Engineering & Tech

TNEB 2016 Assisant Engineer recruitment ECE questions

2016-02-02T12:43:00.001+05:30

Part - 3 (ECE)

1.For a D/A converter, the resolution required is 50mV ad the total maximum input is 10 V.
The number of bits required is

a) 7
b) 8
c) 9
d)200

Ans: Option b)

2. An OPAMP has a slew rate of 100V/msec. For a frequency of 10 MHz, the maximum value of sine wave output voltage will be
a) 100V

b) 50/π V

c) 10 V

d) 5 V

Ans: Option b)

3. The oscillator with the best frequency stability and accuracy is

a) Hartley oscillator

b) Colpitts Oscillator

c) Tickler feedback Oscillator

d) Crystal Controlled Oscillator

Ans: Option d)

4. In Output of a DM speech encoder, the consecutive pulses are of opposite polarity during time interval t1
a) Input to the modulator is essentially constant
b) Modulator is going through slope overload
c) Accumulator is in saturation
d) Speech signal is being sampled at Nyquist rate

Ans: Option a)

5. A silicon diode is operating at 25^oC with a forward bias of 0.6 V and a current of 0.5 A. If the current is held constant at 0.5 A and the temperature of the device is raised to 75^oC, the voltage across the diode is likely to be

a) 0.49 V

b) 0.60 V

c) 0.66 V

d) 0.75 V

Ans: Option a)

6. One of the following microwave diodes is suitable for very low power oscillator

a) Tunnel

b) Gunn

c) IMPATT

d) LSA

Ans: Option a)

7. Frequency Shift Keying is used mostly in

a) Radio Transmission

b) Telegraphy

c) Telephony

d) Television

Ans: Option c)

8. Fourier transform of a unit step signal is

a)    πδ(ω)
b)    1/jω
c)    πδ(ω) + 1/jω
d)    πδ(ω) - 1/jω

Ans: Option c)

9. An Amplifier is said to suffer from distortion when its output is
a) Low
b) different from its input
c) noisy
d) larger than its input

Ans: Option b)

10. Backlash in a stable control system can cause
a) Over damping
b) Low level Oscillations
c) Under damping
d) Poor Stability at reduced values of open loop gain

Ans: Option b)

11. The number of multiplications needed to compute a 32 point DFT using radix-2 FFT algorithm is
a) 80
b) 60
c) 40
d) 20

Ans: Option a)

12. The content of a 4-bit register is 1101. The register is shifted 6 times to the right with serial input being 101101. The final content of register will be
a) 1011
b) 0111
c) 0010
d) 1010

Ans: Option a)

13. Fibers have numerical aperture in the region of 0.15 to 0.4. Fibers with higher N.A. values generally exhibit
a) Reduced losses
b) High bandwidth
c) Reduced losses and low bandwidth
d) Greater losses and low bandwidth

Ans: Option d)

14. A D/A converter has 5V full scale output voltage and an accuracy of ± 0.2%. The maximum error for any output voltage will be

a) 5 mV

b) 10 mV

c) 20 mV

d) 25 mV

Ans: Option b)

15. For a dominant mode, in a rectangular waveguide with breadth 10 cm, the guide wavelength for a signal of 2.5 GHz will be

a) 20cm

b) 18 cm

c) 15 cm

d) 12 cm

Ans: Option c)

16. Radiation from a helical antenna is

a) Plane polarised

b) partially plane polarised

c) Circularly Polarised

d) Elliptically Polarised

Ans: Option c)

17. The cavity magnetron uses strapping to
a) ensure bunching
b) prevent cathode back-heating
c) prevent mode skipping
d) improve phase focusing effect

Ans: Option c)

18. Intrinsic impedance of free space

a) 120Ω

b) 100Ω

c) 277Ω

d) 377Ω

Ans: Option d)

Part II - Basic Engineering and Science

1. Two computers communicating simultaneously comes under the category

a) Serial

b) Full Duplex

c) Half Duplex

d) Simplex

Ans: Option b)

2. The ------------ layer decides the location of synchronization points
a) Network
b) Transport
c) Presentation
d) Session
Ans: Option b)

3. Which of the following addressing modes is convenient to handle pointers?
a) Immediate and Direct addressing
b) Indirect addressing
c) Base addressing
d) Relative addressing

Ans: Option c)

4. Ohm's law is applicable to
a) Silicon Carbide
b) Zener diode
c) Voltage Regulator tube
d) Copper

Ans: Option d)

5. The material in which spontaneous polarization changes with temperature is known as
a) Piezoelectric
b) Ferroelectric
c) Pyroelectric
d) Magneto optic
Ans: Option c)

6. A mode of fracture that is caused by extensive plastic deformation is called
a) Brittle fracture
b) Ductile fracture
c) Plastic fracture
d) Fatigue fracture

Ans: Option d)

7. The dimension of ferromagnetic domains is in the order of

a) 10⁶ m

b) 10^{-9 m}

c) 10^{-6 m}

d) 10^-3 m

^{Ans: Option c)}

8. Which of the following is true? K and σ are thermal and electrical conductivity in a solid, according to Wiedemann-Franz law
a)    KT/ σ = constant
b)    Kσ/T = constant
c)    σ/KT = constant
d)    K/ σT = constant

Ans: Option d)

9. The idea of the quantum nature of light is required to explain
a) interference of light
b) thermionic emission
c) Radioactivity
d) Black body radiation

Ans: Option d)

10. The wavelength of emission from He-Ne laser is
a) 10.64 µ m
b) 337.1 nm
c) 694.3 nm
d) 632.8 nm

Ans: Option a)

11. An optical fibre has a core material of refractive index of 1.55 and cladding material of refractive index of 1.50. The numerical aperture of the fibre is
a) 0.05
b) 0.39
c) 3.05
d) 0.90

Ans: Option b)

12. The increase in order of carbon content of the different types of coal is given by
a) Peat < Sub-bituminous coal < Bituminous Coal < Anthracite
b) Peat < Bituminous coal < Sub -bituminous Coal < Anthracite
c) Anthracite < Sub-bituminous coal < Bituminous Coal < Peat
d) Anthracite < Bituminous coal < Sub-bituminous Coal < Peat

Ans: Option a)

13. Ethernet belongs to
a) IEEE 802.2
b) IEEE 802.3
c) IEEE 802.4
d) IEEE 802.5

Ans: Option b)

14. The purpose of including an external resistance at the time of starting a DC motor is to
a) increase the starting torque
b) increase the armature flux
c) reduce the starting current
d) maintain the constant flux

Ans: Option a)

15. Which of the following can be used to extend the range of an ammeter?
a) A low resistance in series with the ammeter
b) A high resistance in series with the ammeter
c) A low resistance in parallel with the ammeter
d) A high resistance in parallel with the ammeter

Questions on Communication Systems

2016-01-04T23:33:00.000+05:30

1. An AM signal has the form x(t) = [ 10 + 3 cos 3000πt +4 cos 6000πt].cos 2πf_ct, where f_c=10⁶ Hz. The modulation index is ------------------

2. A super heterodyne receiver uses an IF frequency of 455 KHz. The receiver is tuned to a transmitter having a carrier frequency of 2400 KHz. High side band tuning is to be used. The image rejection ratio will be (Q=50)

a) 32.715

b) 35.25

c) 25.715

d) 23.715

3. An angle modulated signal is given by s(t) = Cos 2π ( 2 x 10⁶ t + 30 sin 300 t + 40 cos 300t). The maximum frequency and phase deviation of s(t) are

a) F_m = 11.18 KHz, ∆φ =100

b) F_m = 70.24 KHz, ∆φ =50

c) F_m = 11.18 KHz, ∆φ =100 π

d) F_m = 1.1 KHz, ∆φ =100 π

4. A speech signal band limited to 5 kHz and peak voltage varying between +7V and -3V, is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. The number of quantization levels required to reduce the quantization noise by a factor of √2 would be

a) 1024

b) 512

c) 256

d) 362

5. An analog signal has spectral components from 2 KHz to 7 KHz. What is the minimum band pass sampling rate?

a) 14 KHz

b) 5 KHz

c) 9 KHz

d) 10 KHz

6. A communication channel having AWGN has a bandwidth of 6 KHz and SNR of 7. The highest transmission rate that such a channel can support is

a) 18 Kbps

b) 42 Kbps

c) 16 KPbs

d) 20 Kbps

7. The sum of two signals E₁= 3 sin 4 π x 10³t and E₂= 5 sin 2 π x 256 t are sampled at 1024 Hz.

The sampled signal is passed through a LPF with fc = 2048 Hz. The output of this filter will contain components at

a) only 1024 Hz

b) 256 Hz and 1744 Hz

c) 256 Hz and 1024 Hz

d) only 256 Hz

8. An angle modulated signal is expressed by F(t) = 2 cos (2 x 10⁸π t + 75sin 4 x 10³ π t).

Find the total power and bandwidth of the signal.

a) Pt = 4 Watts; BW = 304 KHz

b) Pt = 152 watts; BW = 4 KHz

c) Pt = 2 watts; BW = 304 KHz

d) Pt = 15 watts; BW = 4 KHz

9. When a radio receiver is tuned to 750 KHz its local oscillator provides the mixer with the input at 1250 KHz. At the output, another signal is also received along with the desired signal. The frequency of the other station is

a) 1750 KHz

b) 1500 KHz

c) 1250 KHz

d) 500 KHZ

10. 25 telephone channels, each band limited to 4 KHz, are to be time division multiplexed(TDM) by using PCM. Calculate the transmission rate of the PCM system for 64 quantization levels and sampling frequency is 1.25 times the Nyquist rate.

a) Rb= 1200 Kbps

b) Rb =750 Kbps

c) Rb =1750 Kbps

d) Rb = 1500 Kbps

11. Which of the following demodulator can be used for demodulating the signal

X(t) = 3( 1 + 2.5 cos 500 πt). Cos 50 10³πt is

a) Envelope detector

b) Synchronous demodulator

c) Square law demodulator

d) All the above

12. 14 signals each band limited to 4 KHz are to be transmitted over a single channel by FDM.

If AM-SSB modulation guard band of 0.75KHz is used, then the bandwidth of the multiplexed signal will be

a) 63.75 KHz

b) 121.75 KHz

c) 37.75 KHz

d) 70 KHz

13. A delta modulator is designed to operate on speech signals limited to 3.4 KHz. The sampling rate is 10 times the Nyquist rate. The step size is 100mV. The modulator is tested with 1KHz sinusoidal signal. The maximum amplitude of the test signal required to avoid slope overload distortion is

a) 1 mV

b) 2.08 mv

c) 2.08 V

d) 1.08 V

14. A source generates four equiprobable symbols. If the source coding is adopted, the average length of the code for 100% efficiency is --------- bits per symbol.

15. An AM wave is given by s(t) = 10( 1 + 0.4 cos 2 π x 10³t + 0.3 cos 2 π x 10⁴ t). Cos 2π x10⁶t.

The following frequency will not be present in the spectrum is/are

a) 1 MHz

b) 2 MHz

c) 1010 KHz, 1001 KHz

d) 990 KHz, 999KHz

16. A source generates 3 symbols with probabilities 1/2, 1/4 and 1/4 at a rate of 2500 symbols per second. Assuming independent generation of symbols, the most efficient source encoder would have average bit rate

a) 3750 bits/sec

b) 1666 bits/sec

c) 4500 bits/sec

d) 3500 bits/sec

17. A single tone frequency modulated wave is processed through a non-linear system y(t) = x²(t). (β and ∆f are modulation index and frequency deviation of original FM wave). The bandwidth required to transmit the output of the non-linear device is

a) 4 ∆f + 4 fm

b) 4 ∆f + 2 fm

c) 2 ∆f + 2 fm

d) 2 ∆f + 4 fm

18. An SSB transmission contains 8kW. This transmission is to be replaced by a standard amplitude modulated signal with same power content. If the modulation index is 0.75, then the upper side band power is -----------------

19. In a multitone modulation, the maximum peak to peak voltage of an AM wave is 14mV and the minimum peak to peak voltage is 6 mV and second modulating wave has modulation index µ = 0.5. The overall modulation index is --------------

20. The frequency deviation of an FM signal is increased from 30 kHz to 60 kHz. For the same sinusoidal modulating signal of 12kHz, the improvement in the demodulated signal to noise power ratio will be ______________

21. To overcome slope over distortion and granular noise problem, which type of integrator is used in Delta modulation?

a) Linear Slope

b) Fixed Slope

c) Companding

d) Variable slope

22. A carrier wave with frequency 8 MHz and peak amplitude value of 10V is DSB-SC amplitude modulated by a 5 kHz sine wave of amplitude 6 V. The amplitude of the side band component is _______

23. The tuned-circuit of the oscillator in an A.M. transmitter uses a 25µH coil and 2.5 nF capacitor. Now if the oscillator output is modulated by audio frequencies upto 5kHz, then the frequency range of side bands would be

a) 631.62 kHz to 641.62 kHz

b) 630 kHz to 645 kHz

c) 630.62 kHz to 646.62 kHz

d) 646 kHz to 656 kHz

24. A 3 V, 1 kHz signal modulates the carrier to cause frequency deviation of 6.5 kHz. On increasing the modulating voltage to 12 V, the frequency deviation is ___________

25. A TDM link has 15 signal channel, each sample is represented by 8 binary bits and it contains an additional bit for synchronisation. If the total bit rate for the TDM link is 1250kbps, then the value of sampling duration (Ts) is ___________

a) 108µs

b) 54µs

c) 125µs

d) 250µs

26. For an AM signal, the bandwidth is 8 kHz and the lowest frequency component present is 800kHz. The carrier frequency used for this AM signal (in kHz) is --------------

Questions on Probability

2015-01-13T00:29:00.001+05:30

1. Five cards are drawn at random one after another from a deck of 52 cards with replacement. The probability that, a spade card occurs at most once is
a) 81/128 b) 27/32 c) 37/64 d) 81/256

2. A bag contains 4 tickets marked AAB, ABA, BAA, BBB. One ticket is drawn at random from the bag. Let Ei(i=1,2,3) denote the event that ith letter on the ticket is B; then which of the following is false?
a) E1 and E3 are independent
b) E2 and E3 are independent
c) E1 and E2 are independent
d) None of these

3.Probability that a factor of 30 ²⁹ is a multiple of 30 ²⁴ is

a) 1/125 b) 6/125 c) 9/125 d)12/125

4. A biased coin is tossed 16 times. If the probability of getting 8 heads is same as that of getting 9 heads, then the probability of getting a head in a single toss is
a) 9/17 b) 8/17 c) 7/17 d) 10/17

5. In 512 sets of rolls of a fair six-sided die, the expected number of sets(rounded off to the nearest integer) in which 12 prime numbers and 3 non-prime numbers occur is
a) 5 b) 4 c) 7 d) 9

6. From a bag containing 8 white and 6 red balls, Ramu selected balls at random at a time first and then Somu selected 3 balls at random at a time without replacing Ramu's balls. Probability that the balls selected by Ramu are all white and that of Somu are all red

a) 5/429 b) 5/143 c) 5/286 d) 7/286

7. Among the aspirants of PSU jobs in BHEL, NTPC and HPCL, of a reputed university, the probabilities of a student getting selected in both BHEL and NTPC, in both NTPC and HPCL, in both HPCL and BHEL and in all the three among BHEL, NTPC and HPCL are 0.4, 0.3, 0.5 and 0.2 respectively. The probability that a student, among these aspirants, getting selected in exactly two of the three PSUs is ---------------------------

8. Two friends decided to meet between 7:00 p.m. and 8:00 p.m. on a certain day at a certain venue. They agreed that whoever arrived first among them at the venue would wait for at most 20 minutes for the other person. Find the probability that they will not meet on that day
a) 4/9 b) 5/9    c) 5/19 d) 13/18

9. Let S = { 0, 1,2,3,............2015}. If a number is selected at random from the set S, the probability that it is a prime factor of 2015 is
a) 3/2015 b) 1/1008 c) 1/226 d) 1/672

10. The probability that Rohan will pass atleast one of the two subjects Maths and Science is 0.6 and the probability that Rohan will pass both Maths and Science is 0.2. Then the sum of the probabilities of Rohan not passing Maths and not passing Science is

a) 0.4 b) 0.8 c) 1.2    d) 1.4

11. Two biased dice are thrown together. On one of them, 6 appears twice as often as any other number while on the other, an odd number appears thrice as frequently as an even number. What is the probability that the sum of the scores on them is 11 0r 12?

a) 1/12             b) 9/28             c) 3/28              d) 5/12

12. For two rolls of a fair die, the probability of getting a prime number in the first roll and a composite number in the second roll is ---------------------

13. Find the probability of a randomly selected leap year having 53 Mondays and 53 Wednesdays.
a) 1/7       b) 2/7      c) 3/7     d) 0

14. Urn 1 contains 14 marbles out of which 4 are blue. Urn 2 contains 16 marbles out of which 6 are blue. If one marble is drawn at random from each Urn simultaneously, the probability of getting exactly one marble is --------------

15. A man speaks truth 2 out of 3 times. He threw a biased coin, that has 60% chance of getting heads and reports that it turned up heads. What is the percentage of chance that it actually turned up on heads?
a) 25% b) 60% c) 66% d) 75%

16. At a certain factory, three machines M1, M2 and M3 manufacture 50%, 30% and 20% respectively, of the total spare parts. Out of this total, 4% of the output of M1, 2% of that of M2 and 5% of that of M3 end up being defective. If a randomly drawn spare part from the total output is defective, find the probability that the part was manufactured by either M1 or M3.
a) 4/5 b) 5/6 c) 11/12 d)1/6

17. An event is called statistically independent if
a) The probability of occurrence of one event is not affected by the occurrence of the other event.
b) The probability of occurrence of one event is affected by the occurrence of the other event.
c) The probability of occurrence of one event is affected by the occurrence of same event.
d) Non of these

Ans: Option a)

18. A fair coin is tossed 4 times, the probability that at least once head turns up is
a) 1/16
b) 15/16
c) 7/8
d) 1/8

19. The probability that Anil speaks truth is 4/5 while that of Bindu is 3/4, the probability that they are likely to contradict each other in stating the same fact is
a) 3/20
b) 4/5
c) 7/20
d) 1/5

20. Probability that at least one of the events A and B occur is 2/3 and probability that both the events A and B occur is 1/6. Then the value of P(A^c ) + P(B^c ) is

a) 7/6 b) 6/7 c) 6/5 d)5/6

21. Find the probability that a two-digit number selected randomly from all the two-digit numbers between 1 and 100 is divisible by neither 3 nor 5.

a) 8/15 b) 3/5 c) 2/5 d) 7/15

22. Find the probability that a two-digit number selected randomly from all the two-digit numbers between 1 and 100 is divisible by neither 3 nor 5.

a) 8/15 b)3/5 c)2/5 d)7/15

23. For a biased coin, when tossed 12 times, probability of getting exactly 7 heads is same as probability of getting exactly 6 heads. Then the probability of getting heads, when that coin is tossed once is --------------------

a) 5/13 b) 8/13 c) 6/13 d) 7/13

24. A bag contains 5 red balls 8 green balls. Two balls are drawn from the bag one after another without replacing the first ball. What is the probability that both balls are different color?

a) 10//39 b) 5/39 c) 5/13 d) 20/39

25. What is the probability that a quadratic equation ax²+bx+c has equal roots if a,b and c are distinct and are taken from {1,2,3,4,6,8,9}

a) 1/35 b) 2/35 c) 1/105 d) 2/105

26. An unbiased coin is tossed six times. The outcome of each toss is either head or tail. The probability of getting at least two heads is --------------

IES 2009 E & T Solved Question paper 2 Objective

2014-06-23T12:33:00.001+05:30

1. Consider the following:

1. Oscillator

2. Emitter follower

3. Cascaded amplifier

4. Power amplifier

Which of these use feedback amplifiers?

a) 1 and 2

b) 1 and 3

c) 2 and 4

d) 3 and 4

Ans: Option a)

2. Why npn-transistors are preferred over pnp transistors?

a) Leakage current in NPN-transistors is less than pnp-transistors.

b) Mobility of majority carrier in npn-transistors is greater than the mobility of majority carriers in pnp-transistors.

c) Bias voltage required in npn is less than in pnp-transistors.

d) Bias voltage required in npn is greater than in pnp-transistors.

Ans: Option b)

3. Consider the following statements

To draw a.c. equivalent circuit of a transistor all

1. d.c. sources are shorted

2. a.c. sources are shorted

3. d.c. sources are opened

4. a.c. sources are connected to d.c. sources

Which of the above statements is/are correct?

a) 2 and 4

b) 1 and 2

c) 1 only

d) 3 and 4

Ans: Option c)

4. Which one of the following statements is not correct with regard to power amplifiers?

a) The collector current is large

b) They are used as the front end of multistage amplifier

c) They are used near the end of multistage amplifier

d) They have a high power rating (>1/2 W)

Ans: Option b)

5. Consider the following statements regarding the Class-B power amplifiers(Complementary symmetry type):

1. The efficiency of the amplifier is higher than that of Class-A amplifier

2. The power output is low

3. Cross-over distortion is present

4. The standby power dissipation is absent

Which of the above statements are correct?

a) 1,2 and 3

b) 1,2 and 4

c) 1, 3 and 4

d) 2, 3 and 4

Ans: Option c)

6. Consider the following:

1. Distortion

2. Gain

3. Bias Stabilization

4. Sensitivity

5. Frequency Response

Which of these properties of the power amplifier one should concentrate upon while designing a good power amplifier circuit?

a) 1, 2 and 3

b) 1, 3 and 5

c) 2, 3 and 4

d) 4 and 5

Ans: Option a)

7. Consider the following:

1. Coupling Capacitor

2. Emitter by-pass capacitor

3. Emitter to base diffusion capacitance of the BJT

4. Stray capacitance of the circuit.

Which of these components in a R-C coupled amplifier control the lower cut-off frequency of the amplifier?

a) 1 and 2

b) 2 and 3

c) 3 and 4

d) 1 and 4

Ans: Option a)

8. Which one of the following is a regulated power supply?

a) IC 555

b) IC 844

c) IC 3080

d) IC 723

Ans: Option d)

9. Consider the following statements regarding an OP-AMP:

1. All types of negative feedback reduce non-linear distortion

2. All types of negative feedback reduce the output offset voltage

3. Non-inverting (current and voltage) feedback increases the input impedance

4. Inverting (current and voltage) feedback decreases the input impedance

Which of the above statements is/are correct?

a) 1 only

b) 2 and 3 only

c) 2 and 4 only

d) 1, 2, 3 and 4

Ans: Option d)

10. Consider the following statements:

The bias stability of an emitter-bias amplifier circuit improves by

1. Decreasing the value of R_B.

2. Increasing the value of R_E.

3. Decreasing the value of R_E.

4. Increasing the value of R_B.

5. Increasing the value of R_C.

Which of the above statements are correct?

a) 1 and 2

b) 2 and 3

c) 3 and 4

d) 4 and 5

Ans: Option a)

11. Which of the following will be true for a CE transistor amplifier if the emitter resistor value is made equal to zero?

1. Its gain will increase.

2. Its stability will increase.

3. Its gain will decrease.

4. Its stability will decrease.

Select the correct answer from the codes given below:

a) 1 and 2

b) 2 and 3

c) 3 and 4

d) 1 and 4

Ans: Option d)

12. Which one of the following circuits is used for converting a sine wave into square wave?

a) Astable multivibrator

b) Monostable Multivibrator

c) Bistable Multivibrator

d) Schmitt Trigger

Ans: Option d)

13. Which of the transistor models is most preferred for the analysis of a transistor circuit both at mid-band and at high frequencies?

a) h-parameter model

b) y-parameter model

c) s-parameter model

d) hybrid-π model

Ans: Option d)

14. Which of the following describe the correct properties of an emitter follower circuit?

1. It is a voltage series feedback circuit.

2. It is a current series feedback circuit.

3. Its voltage gain is less than unity.

4. Its output impedance is very low.

Select the correct answer from the codes given below:

a) 1, 3 and 4

b) 2, 3 and 4

c) 2 and 3 only

d) 2 and 4 only

Ans: Option a)

15. Which one of the following type of negative feedback increases the input resistance and decreases the output resistance of an amplifier?

a) Current series feedback

b) Voltage series feedback

c) Current shunt feedback

d) Voltage shunt feedback

Ans: Option b)

16.Which one of the following oscillators is well suited for the generation of wide range audio frequency sine waves?

a) RC phase-shift oscillator

b) Wien-bridge oscillator

c) Col-pitts oscillator

d) Hartley oscillator

Ans: Option b)

17. Consider the following statements regarding a good power supply:

1. The a.c. ripple should be high

2. S_v, (Voltage stability factor) should be low

3. S_T, (Temperature stability factor) should be low.

Which of the above statements are correct?

a) 1, 2 and 3

b) 2 only

c) 3 only

d) 2 and 3 only

Ans: Option d)

18. Which of the following are the non-linear applications of OP-AMP?

1. Current-to-voltage convertor

2. Comparator

3. Peak detector

4. Limiter

Select the correct answer from the codes given below:

a) 1, 2 and 3

b) 2, 3 and 4

c) 1, 3 and 4

d) 1, 2 and 4

Ans: Option b)

19. Consider a 565 PLL with R_T = 10 KΩ and C_T = 0.01 μF. What is the output frequency of the VCO?

a) 10 kHz

b) 5 kHz

c) 2.5 kHz

d) 1.25 kHz

Ans: Option c)

20. Which of the following does not show non-linear V-I characteristics?

a) Schottky diode

b) Tunnel diode

c) Thermistor, at a fixed temperature

d) p-n junction diode

Ans: Option c)

21. Which of the following conditions must be satisfied for a transistor to remain under saturation?

1. Its collector to base junction should be under forward bias.

2. Its collector to base junction should be under reverse bias.

3. Its emitter to base junction should be under reverse bias.

4. Its emitter to base junction should be under forward bias.

Select the correct answer from the codes given below:

a) 1 and 2

b) 1 and 3

c) 2 and 3

d) 1 and 4

Ans: Option d)

22. Which junction has least junction capacitance?

a) Alloy

b) Grown

c) Diffused

d) Point contact

Ans: Option d)

23. Assertion (A): A fixed bias BJT circuit exhibits better performance as compared to a self bias BJT circuit.

Reason (R) : A fixed bias BJT circuit uses less components as compared to self bias BJT circuit.

a) Both A and R are individually true and R is the correct explanation of A

b) Both A and R are individually true but R is not the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

24. Assertion (A): The small signal analysis of a transistor amplifier is done to obtain the current gain, voltage gain and the conversion efficiency of an amplifier.

Reason (R): The small signal analysis of a transistor amplifier uses the small signal parameter of the transistor.

a) Both A and R are individually true and R is the correct explanation of A

b) Both A and R are individually true but R is not the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

25. Assertion (A): A rectifier with inductor filter is more efficient for high load current.

Reason(R): In rectifier with inductor filter we can use a larger choke to reduce ripple, larger choke will have higher dc resistance which will result in lower dc output voltage for higher load current.

a) Both A and R are individually true and R is the correct explanation of A

b) Both A and R are individually true but R is not the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option a)

26. Assertion (A): It is not desirable to drive a transistor into hard saturation in high speed switching circuits.

Reason (R): It may not be possible to bring it back to cut off state, if it is driven into hard saturation

a) Both A and R are individually true and R is the correct explanation of A

b) Both A and R are individually true but R is not the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option c)

27. What are the ultimate purposes of minimizing logic expressions?

1. To get a small size expression.

2. To reduce the number of variables in the given expression.

3. To implement the function of the logic expression with least hardware.

4. To reduce the expression for making it feasible for hardware implementation.

Select the correct answer from the codes given below:

a. 1 only

b. 2 and 3

c. 3 only

d. 3 and 4

Ans: Option d)

28. Which of the following factors are responsible to design IC logic gates to operate at a fixed supply voltage of 5 volts?

1. Low heating of IC logic gates.

2. Compatibility with other logic gates.

3. Satisfactory and safe operation.

4. Standardization from IC Manufacturing point of view.

Select the correct answer from the below codes:

a) 1 only

b) 2 only

c) 2 and 3

d) 3 and 4

Ans: Option c)

29. Which of the following statements is not correct?

a) Propagation delay is the time required for a gate to change its state.

b) Noise immunity is the amount of noise which can be applied to the input of a gate without causing the gate to change state

c) Fan-in of a gate is always equal to fan-out of the same gate

d) Operating speed is the maximum frequency at which digital data can be applied to a gate

Ans: Option c)

30. Which of the following are universal gates?

1. NAND

2. NOR

3. XOR

Select the correct answer from the codes given below:

a) 1 and 2 only

b) 1 and 3 only

c) 2 and 3 only

d) 1,2 and 3

Ans: Option a)

31. Which of the following output configurations are available in a TTL gate?

1. Open collector output

2. Totem-pole output

3. Tristate output

Select the correct answer from the codes given below

a) 1 only

b) 1 and 2 only

c) 2 and 3 only

d) 1,2 and 3

Ans: Option d)

32. Which one of the following logic families can be operated using a supply voltage from 3V to 15V?

a) TTL

b) ECL

c) PMOS

d) CMOS

Ans: Option d)

33. Which of the following circuits come under the class of combinational logic circuits?

1. Full adder

2. Full subtractor

3. Half adder

4. J-K Flip-flop

5. Counter

Select the correct answer from the codes given below:

a) 1 only

b) 3 and 4

c) 4 and 5

d) 1, 2 and 3

Ans: Option d)

34. Consider a multiplexer with X and Y as data inputs and Z as control input. Z = 0 selects input X and Z = 1 selects input Y. What are the connections required to realize the 2-variable Boolean function f = T + R, without using any additional hardware?

a) R to X, 1 to Y, T to Z

b) T to X, R to Y, T to Z

c) T to X, R to Y, 0 to Z

d) R to X, 0 to Y, T to Z

Ans: Option a)

35. With which decoder it is possible to obtain many code conversions?

a) 2 line to 4 line

b) 3 line to 8 line

c) not possible with any decoder

d) 4 line to 16 line decoder

Ans: Option d)

36. Match List-I (Application of Circuits) with List-II (Circuit name) and select the correct answer using the correct code given below the lists:

List-I

A. Divider

B. Clips input voltage at two pre-determined levels

C. Square wave generator

D. Narrow current pulse generator

List-II

1. Astable multivibrator

2. Schmitt trigger

3. Bistable Multivibrator

4. Blocking Oscillator

Codes:

A B C D

a) 4 2 1 3

b) 3 2 1 4

c) 4 1 2 3

d) 3 1 2 4

Ans: Option d)

37. Consider the following statements:

For a master-slave J-K Flip-flop,

1. The toggle frequency is the maximum clock frequency at which the flip-flop will toggle reliably.

2. The data input must precede the clock triggering edge transition time by some minimum time.

3. The data input must remain fixed for a given time after the clock triggering edge transition time for reliable operation.

4. Propagation delay time is equal to the rise time and fall time of the data.

Which of the above statements is/are correct?

a) 1, 2 and 3

b) 1 and 2 only

c) 2 and 3 only

d) 3 and 4 only

Ans: Option a)

38. Consider the following statements:

1. A flip-flop is used to store 1-bit of information.

2. Race-around condition occurs in a J-K flip-flop when both the inputs are 1.

3. Master-slave configuration is used in flip-flops to store 2-bits of information.

4. A transparent latch consists of a D-type flip-flop

Which of the above statements is/are correct?

a) 1 only

b) 1, 3 and 4

c) 1, 2 and 4

d) 2 and 3 only

Ans: Option c)

39. Which of the following flip-flops is used as a latch?

a)J-K flip-flop

b) R S flip-flop

c) T flip-flop

d) D flip-flop

Ans: Option d)

40. Which of the following conditions should be satisfied to call an astable multivibrator circuit using discrete components as a digital circuit?

1. A flip-flop is always a digital circuit.

2. Only when we assign 1 and 0 to the high and low a level of the output, a flip-flop is called a digital circuit.

3. Only if the power supply voltage is maintained at +5V or -5V, it is called a digital circuit

4. Only if it is in IC form, following the technology of IC Manufacture, it is called a digital circuit.

Select the correct answer from the codes given below:

a) 1 only

b) 2 and 3

c) 2 only

d) 3 and 4

Ans: Option a)

41. Which of the following Boolean algebra rules is correct?

a) A.A’ = 1

b) A + AB = A+ B

c) A + A’B = A+ B

d) A(A+B) = B

Ans: Option c)

42. Which of the following comes under the class of sequential logic circuits?

1. Full adder

2. Full subtractor

3. Half adder

4. J-K Flip-flop

5. Counter

Select the correct answer from the codes given below:

a) 1 and 2

b) 2 and 3

c) 3 and 4

d) 4 and 5

Ans: Option d)

43. Consider the following statements regarding registers and latches:

1. Registers are made of edge triggered FFs whereas latches are made from level-triggered FFs.

2. Registers are temporary storage devices whereas latches are not

3. A latch employs cross-coupled feedback connections.

4. A register stores a binary word whereas a latch does not.

Which of the above statements is/are correct?

a) 1 only

b) 1 and 3

c) 2 and 3

d) 3 and 4

Ans: Option b)

44. Which of the following abilities are available in a universal Shift register?

1. Shift Left

2. Shift Right

3. Parallel Load

4. Serial add

Select the correct answer from the codes given below:

a) 2 and 4 only

b) 1, 2 and 3

c) 1, 2 and 4

d) 1, 3 and 4

Ans: Option b)

45. Which of the following measurements can be done using a counter?

1. Pulse duration

2. Interval between two pulses

3. Amplitude of the pulse

4. Rise time of a pulse

Select the correct answer from the codes given below:

a) 1 and 2

b) 2 and 3

c) 1 and 4

d) 2 and 4

Ans: Option a)

46. Match List-I (Type of N-bit ADC) with List-II (Characteristics) and select the correct answer using the codes given below the lists:

List-I

A. Flash Converter

B. Successive Approximation

C. Counter Ramp

D. Dual Slope

List-II

1. Integrating Type

2. Fastest converter

3. Maximum conversion time = N bits

4. Uses a DAC in its feedback path

Codes:

a) 2 3 4 1

b) 1 3 4 2

c) 2 4 3 1

d) 1 4 3 2

Ans: Option a)

47. In which one of the following types of analog to digital converters the conversion time is practically independent of the amplitude of the analog signal?

a) The dual slope integrating type

b) Successive Approximation Type

c) Counter ramp type

d) Tracking type

Ans: Option b)

48. Assertion (A): When all inputs of a NAND gate are shorted to get a one input, one output gate, it becomes an inverter.

Reason (R): When all inputs of a NAND-gate are at logic ‘0’ level, the output is at logic ‘1’.

a) Both A and R are individually true and R is the correct explanation of A

b) Both A and R are individually true but R is not the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

49. Which of the following statements about the matched filter in a communication receiver are correct?

1. Its impulse response depends on the signal shape.

2. It maximizes the SNR at the detection stage.

3. It produces ISI.

4. It may produce phase error if synchronization is improper.

Select the correct answer from the codes given below:

a) 1 and 4 only

b) 1 and 2 only

c) 2, 3 and 4

d) 1,2 and 4

Ans: Option b)

50. A single mode fibre does not suffer from which type of dispersion?

a) Waveguide dispersion

b) Material dispersion

c) Intermodal dispersion

d) Polarization mode dispersion

Ans: Option c)

51. A balanced modulator is used in the generation of which of the following?

a) DSB-SC signal

b) FM signal

c) PM signal

d) PAM signal

Ans: Option a)

52. An amplitude modulated signal occupies a frequency range from 395 kHz to 405 kHz. It can be demodulated by which of the following?

a) Using an envelope detector and filter

b) Multiplying with a 395 kHz local signal

c) Multiplying with a 405 kHz local signal

d) Low pass filtering with cut off at 400 kHz

Ans: Option d)

53. An audio signal is band limited to 4 kHz. It is sampled at 8 kHz. What will be the spectrum of the sampled signal?

a) -4 kHz to 4 kHz

b) -8 kHz to 8 kHz

c) every 4n kHz and repeating

d) every +- 8 kHz and repeating as well as at zero (k integer)

Ans: Option d)

54. A signal occupies a band 5 kHz to 10 kHz. For proper error free reconstruction at what rate it should be sampled?

a) 10 kHz

b) 20 kHz

c) 5 kHz

d) (10 + 5) x 2 kHz

Ans: Option a)

55. The spectral range of a band pass signal extends from 10 MHz to 10.4 MHz. What is the minimum sampling frequency required for reconstruction?

a) 20 MHz

b) 20.8 MHz

c) 20.4 MHz

d) 0.8 MHz

Ans: Option d)

56. An audio signal is to be transmitted digitally. Which is the system best suited for good fidelity?

a) 8 bit PCM

b) 13 bit PCM

c) 32 bit PCM

d) PCM system with non-uniform quantizer

Ans: Option d)

57. For good quality signal transmission all frequency components should have the same transmission delay, t_d and same phase shift -ᵠ s. What can be said about the statement?

a) correct

b) True for t_d but not for ᵠ s

c) Not true for t_d but true for ᵠ s

d) Both t_d and ᵠ s are not involved in the equality

Ans: Option b)

58. Which of the following introduces mode partition noise?

a) coaxial line

b) Waveguide

c) Fibre transmission line

d) Both coaxial line ans waveguide

Ans: Option c)

59. Which of the following doesn’t cause losses in optical fibre cables?

a) Impurities

b) Microbending

c) Attenuation in glass

d) Stepped index operation

Ans: Option d)

60. On which bands, do the optical fibres operate?

1. Ultra violet band

2. Ultra high frequency band

3. Visible light band

4. Infra red band

Select the correct answer from the codes given below:

a) 1 only

b) 1 and 2 only

c) 1, 2 and 3

d) 1, 3 and 4

Ans: Option d)

61. Which one of the following photo-detector doesn’t provide gain?

a) Photo-transistor

b) Photo conductor

c) Avalanche photodiode

d) p-i-n photodiode

Ans: Option d)

62. Consider the following statements:

In case of space wave propagation, the signal strength at the receiver is

1. Directly proportional to transmitter and receiver heights

2. Inversely proportional to distance between transmitter and receiver

3. Directly proportional to the frequency.

Which of the above statements is/are correct?

a) 1 and 2

b) 1 and 3

c) 2 and 3

d) 3 only

Ans: Option b)

63. What was the first commercial geostationary communication satellite?

a) INTELSAT 1

b) ECHO

c) INSAT-1A

d) SPUTNIK

Ans: Option a)

64. What does a link budget for satellite communication include?

a) Total cost of the satellite

b) Cost of satellite plus launch vehicle

c) Signal and noise levels in dB

d) Margins of error permitted

Ans: Option c)

65. Which one of the following statements is correct?

a) AGC in radio receivers will keep the total signal output fairly constant but the noise component will be reduced, with the result S/N ratio will improve

b) AGC in radio receivers is a linear operation w.r.t both signals and noise

c) Sudden changes in the output while tuning which may cause damage to the components, is an unavoidable feature of AGC

d) AGC operation is independent of filter components used in the AGC circuit.

Ans: Option c)

66. Consider the following statements:

1. Taking 2’s complement representation is equivalent to sign change.

2. In the 2’s complement representation the most significant bit (MSB) is zero for a positive number.

3. In a 4 bit binary representation of a binary number A, A + 1’s complement of A = 2⁴.

Which of the above statements are correct?

a) 1 and 2 only

b) 1 and 3 only

c) 2 and 3 only

d) 1, 2 and 3

Ans: Option a)

67. Consider the following statements:

1. Strictly speaking C supports 1 dimensional array only.

2. An array element may be an array by itself.

3. Array elements need not occupy contiguous memory locations.

Which of the above statements is/are correct?

a) 1 only

b) 2 only

c) 1 and 2

d) 2 and 3

Ans: Option b)

68. What can be the maximum dimension of an array in C language program>

a) 3

b) 4

c) 5

d) It is compiler dependent

Ans: Option d)

69. With reference to C programming language, which of the following statements are correct?

1. An identifier may start with an underscore.

2. An identifier may end with an underscore.

3. IF is a valid identifier.

4. The number of significant characters in an identifier is implementation dependent.

Select the correct answer from the codes given below:

a) 1 and 2 only

b) 2 and 3 only

c) 1, 2, 3 and 4

d) 3 and 4 only

Ans: Option c)

70. How many distinct binary trees can be constructed with three nides?

a) 1

b) 2

c) 3

d) 5

Ans: Option d)

71. Consider the following statements:

1. Internal sorting is used if the number of items to be sorted is very large.

2. External sorting is used if the number of items to be sorted is very large.

3. External sorting needs auxiliary storage.

4. Internal sorting needs auxiliary storage.

Which of the above statements are correct?

a) 1 and 2

b) 2 and 3

c) 3 and 4

d) 2 and 4

Ans: Option b)

72. Which of the following has a major role in implementation of function calls in C?

a) Processor’s register

b) Data segment

c) The heap

d) System stack

Ans: Option d)

73. Which one of the following algorithms design techniques is used in quick sort algorithms?

a) Dynamic programming

b) Back tracking

c) Divide and conquer

d) Greedy

Ans: Option c)

74. There are four different algorithms A1, A2, A3 and A4 to solve a given problem with the complexity order log (n), log (log (n)), n log(n) and n/log(n) respectively.

Which is the best algorithm?

a) A1

b) A2

c) A3

d) A4

Ans: Option b)

75. Which of the following is/are correct statement (s)?

1. Bus is a group of wires carrying information.

2. Bus is needed to achieve reasonable speed of operation.

3. Bus can carry data or address.

4. A bus can be shared by more than one device.

Select the correct answer from the codes given below:

a) 1 only

b) 1 and 2 only

c) 2, 3 and 4 only

d) 1, 2, 3 and 4

Ans: Option d)

76. Which of the following is included in the architecture of a computer?

1. Addressing modes, CPU

2. Instruction set, data formats

3. Secondary memory, Operating system

Select the correct answer from the codes given below:

a) 1 and 2

b) 1 and 3

c) 2 and 3

d) 3 only

Ans: Option a)

77. A 3 x 8 decoder with two enable inputs is to be used to address 8 blocks of memory. What will be the size of each memory block when addressed from a sixteen bit bus with two MSBs used to enable the decoder?

a) 2 K

b) 4 K

c) 16 K

d) 64 K

Ans: Option a)

78. Match List-I (Type of Memory) with List-II (Used as) and select the correct answer using the code given below the lists:

List-I

A. DRAM

B. SRAM

C. Parallel Access Registers

D. ROM

List-II

1. Cache Memory

2. Main Memory

3. BIOS Memory

4. CPU registers

Code:

A B C D

a) 1 4 2 3

b) 3 4 2 1

c) 1 2 4 3

d) 3 2 4 1

Ans: Option c)

79. Which of the following are the memory performance parameters?

1. Access time and latency

2. Block size and Block access time

3. Cycle time and bandwidth

Select the correct answer from the codes given below:

a) 1 only

b) 1 and 2 only

c) 2 and 3 only

d) 1, 2 and 3

Ans: Option d)

80. What is the address space of 8086 CPU?

a) One Megabyte

b) 256 kilobyte

c) 1 K Megabytes

d) 64 kilobytes

Ans: Option a)

81. Which of the following counters can be used to divide the clock frequency of the microprocessor by 5?

a) 3 bit counter

b) 5 bit counter

c) mod 3 counter

d) mod 5 counter

Ans: Option d)

82. Identification of highest priority interrupt can be achieved in a minimum time by which of the following schemes?

a) Hardwired polling

b) Priority encoder circuit

c) Software polling

d) Subdivision of interrupt registers into a number of sub-registers which are checked parallel

Ans: Option a)

83. Which of the following is used as the interface chip for data transmission between 8086 and a 16-bit ADC?

a) 8259

b) 8255

c) 8253

d) 8251

Ans: Option b)

84. Which one of the following addressing modes is used in the instruction PUSH B?

a) Direct

b) Register

c) Register Indirect

d) Immediate

Ans: Option b)

85. What is the purpose of a start bit in RS232 serial communication protocol?

a) To synchronize receiver for receiving every byte.

b) To synchronize receiver for receiving a sequence of byte.

c) Acts as a parity bit

d) To synchronize receiver for receiving the last byte.

Ans: Option b)

86. The resolution of a DAC depends on which of the following?

a) The number of bits

b) Monotonocity

c) Reference

d) The values of resistance

Ans: Option a)

87. What is the purpose of DMA facility in microprocessor based system?

a) To increase the speed of data transfer between the μP and I/O devices.

b) To increase the speed of data transfer between the μP and memory.

c) To increase the speed of data transfer between the memory and the I/O devices.

d) To improve the reliability of the system.

Ans: Option c)

88. Personal Computer cannot be used for which one of the following?

a) Game Playing

b) Weather Forecasting

c) Office Automation

d) Home Computing

Ans: Option b)

89. What is the characteristic of a good control system?

a) Sensitive to parameter variation.

b) Insensitive to input command.

c) Neither sensitive to parameter variation nor sensitive to input commands.

d) Insensitive to parameter variation but sensitive to input commands.

Ans: Option d)

90. How can the bandwidth of a control system be increased?

a) By the use of phase lead network.

b) By the use of phase lag network.

c) By the use of both phase-lag and phase-lead network.

d) By the use of cascaded amplifiers in the system.

Ans: Option a)

91. Which of the following may result in instability problem?

a) Large error

b) High Selectivity

c) High Gain

d) Noise

Ans: Option c)

92. A negative feedback closed-loop system is supplied to an input of 5V. The system has a forward gain of 1 and a feedback gain of 1. What is the output voltage?

a) 1.0 V

b) 1.5 V

c) 2.0 V

d) 2.5 V

Ans: Option d)

93. For what positive value of K does the polynomial

s⁴+ 8s³+ 24s²+32s+K

Have roots with zero real parts?

a) 10

b) 20

c) 40

d) 80

Ans: Option d)

94. How many roots with positive real parts do the equation s³ + s² – s + 1 = 0 have?

a) Zero

b) One

c) Two

d) Three

Ans: Option c)

95. The characteristics equation of a control system is given as

s⁴ + 8s³ + 24s² + 32s + K = 0

What is the range of values of K for this system to be stable?

a) 0 <= K< 80

b) 0 <= K< 100

c) 0 <= K< 300

d) 0 <= K< 600

Ans: Option a)

96. Which of the following can be used as a tacho generator in control system?

a) Microsyn

b) DC servomotor

c) AC servomotor

d) Magnetic amplifier

Ans: Option c)

97. Consider the equation

s² + 2s + k (s+2) = 0

Where do the roots of this equation break on the root loci plot?

a) -3.414

b) -2.414

c) -1.414

d) -.0.414

Ans: Option a)

98. How many number of branches does the root loci of the equation

s(s+2)(s+3)+K(s+1) = 0 have?

a) Zero

b) One

c) Two

d) Three

Ans: Option d)

99. The characteristic equation of a control system is given as

s⁴ + 4s³ + 4s² + 3s + K = 0

What is the value of K for which this system is marginally stable?

a) 9/16

b) 19/16

c) 29/16

d) 39/16

Ans: Option d)

100. The transfer function of a controller is given as K_p + K_d.s where K_p and K_d are constant. What type of controller is this?

a) Proportional

b) Proportional plus integral

c) Proportional plus derivative

d) Integral plus derivative

Ans: Option c)

101. The transfer function of a linear-time-invariant system is given as 1/(s+1). What is the steady-state value of the unit-impulse response?

a) Zero

b) One

c) Two

d) Infinite

Ans: Option a)

102. Consider the function F(s) = w/ (s² + w²) where F(s) is the Laplace transform of f(t). What is the steady state value of f(t)?

a) Zero

b) One

c) Two

d) A value between –1 and +1

Ans: Option d)

IES 2009 E & T Solved Question paper 1 Objective

2014-05-25T19:22:00.001+05:30

1. Which of the following statements is/are true for the diamond structure?
i. Coordination number is four

ii. Packing fraction is 0.34

iii. Copper crystallizes into diamond structure

iv. Lattice is FCC

Select the correct answer using the codes given below:

a) i only

b) i,ii and iv

c) ii and iii only

d) ii, iii and iv

Ans: Option b)

2. Which of the following statements is/are true for a good conductor of electricity?

i. Its conductivity decreases with increasing temperature

ii. Number of free electrons is around 10²⁶ m^-3

iii. Its conductivity decreases with addition of impurities

iv. It is a good conductor of heat also

Select the correct answer using the codes given below:

a) i, ii, iii and iv

b) i only

c) ii and iii only

d) iii and iv only

Ans: Option a)

3. Which of the following materials is not an insulator?

a) Diamond

b) Graphite

c) Bakelite

d) Lucite

Ans: Option b)

4. Consider the following statements:

The conductivity of a metal has negative temperature coefficient since:

i. The electron concentration increases with temperature

ii. The electron mobility decreases with temperature

iii. The electron-lattice scattering rate increases with temperature.

Which of the above statements is/are correct?

a) i only

b) i and ii

c) ii and iii

d) iii only

Ans: Option c)

5. Which of the following is not conducting material?

a) Copper

b) Tungsten

c) Germanium

d) Platinum

Ans: Option c)

6. What is the chemical bonding in silicon semiconductor?

a) Metallic

b) Ionic

c) Covalent

d) Van der Waals

Ans: Option c)

7. Which of the following is a trivalent material?

a) Antimony

b) Phosphorous

c) Arsenic

d) Boron

Ans: Option d)

8. The fuse material used in electrical lines must have which one of the following properties?

a) High resistivity

b) Low conductivity

c) High melting point

d) Low melting point

Ans: Option d)

9. Manganin, an alloy of copper and manganese is used in

a) Soldering material

b) Heating elements

c) Ballast resistors

d) Standard resistances

Ans: Option d)

10. Which if the following pairs is not correctly matched?

a) NaCl Diamagnetic

b) Gd Paramagnetic

c) Ferrite Ferrimagnetic

d) Cr2O3 Ferromagnetic

Ans: Option b)

11. Hysteresis loss in a transformer working at 220 V and at frequency of 50 Hz is 100 W. When the transformer is operated at 220 V and at a frequency of 100 Hz, What is the hysteresis loss?

a) 50 W

b)100 W

c) 200 W

d) 400 W

Ans: Option c)

12. Which of the following is not an electro-magnetic device?

a) Hall Transducer

b) Transformer

c) Speedometer

d) Eddy current damping device

Ans: Option a)

13. Which one of the following materials is used for making permanent magnets?

a) Steel

b) Carbon

c) Carbon-Steel

d) Graphite

Ans: Option c)

14. What happens when a paramagnetic material is heated above Curie temperature?

a) It becomes diamagnetic

b) It becomes non-magnetic

c) It becomes ferromagnetic

d) It becomes anti-ferromagnetic

Ans: Option a)

15. Ferromagnetic materials show hysteresis in B-H characteristic. As the magnetic field is increased slowly from zero value, What is the first process which sets in the material to give net magnetization?

a) Growth of favorably oriented domains at the cost of other domains by reversible boundary displacements.

b) Growth of favorably oriented domains at the cost of other domains by irreversible boundary displacements.

c) Domain wall orientation

d) A combination of processes a) and c) above

Ans: Option d)

16. The following properties are associated with ferroelectric materials:

i) Its susceptibility is negative.

ii) The susceptibility is expressed as χ = C/ (T – Tc)

Where C is the curie temperature.

iii) It has permanent dipoles oriented randomly

Which of the above statements is/are correct?

a) i only

b) i and iii

c) ii only

d) i, ii and iii

Ans: Option c)

17. The materials not having negative temperature coefficient of resistivity are

a) Metals

b) Semiconductors

c) Insulators

d) None of the above

Ans: Option a)

18. Consider the following:

i) Si

ii) Ge

iii) GaAs

iv) InP

Which of the following semiconductors should be used for making highly efficient photodiodes?

a) i and iv only

b) iii and iv only

c) i, iii and iv

d) ii, iii and iv

Ans: Option b)

19. Which of the following compounds is widely used for making ferrites?

a) FeO

b) CuO

c) MgO

d) Fe2O3

Ans: Option d)

20. Effective Q of the equivalent electric circuit of quartz crystal is of the order of

a) 200

b) 2000

c) 20,000

d) 2,00,000

Ans: Option c)

21. In a material, the fermi-level is located between the center of the forbidden band and the conduction band. Then what is that material?

a) A p-type semiconductor

b) A n-type semiconductor

c) An intrinsic semiconductor

d) An insulator

Ans: Option b)

22. Consider the following statements:

1) Acceptor level is formed very close to the conduction band.

2) The effective mass of the free electron is same as that of a hole.

3) The magnitude of the charge of a free electron is same as that of a hole.

4) Addition of donor impurities adds holes to the semiconductor

Which of the following statements are correct?

a) 1 and 3

b) 2 and 3

c) 2 and 4

d) 3 and 4

Ans: Option b)

23. Diffusion current of holes in a semiconductor is proportional to ( with p = concentration of holes/unit volume)

a) dp/dx²

b) dp/dx

c) dp/dt

d) d²p/dx²

Ans: Option b)

24. The junction capacitance of linearly graded pn-junction (with applied voltage = VB) is proportional to

a) V_B^1/2

b)V_B^-1/2

c) V_B^1/3

d) V_B^-1/3

Ans: Option d)

25. As per Hall effect, if any specimen carrying a current I is placed in a transverse magnetic field B, then an electric field E is induced in the specimen in the direction

a) parallel to I

b) perpendicular to B and parallel to I

c) parallel to I and B

d) perpendicular to both I and B

Ans: Option d)

26. Which of the following quantities cannot be measured/determined using Hall effect?
a) Type of semiconductor ( p or n)
b) Mobility of charge carriers
c) Diffusion constant
d) Carrier concentration

Ans: Option c)

27. A junction FET can be used as a voltage variable resistor
a) at pinch-off condition
b) beyond pinch-off voltage
c) well below pinch-off condition
d) for any value of V_DS

Ans: Option c)

28. The maximum power dissipation capacity of a transistor is 50 mW. If the collector emitter voltage is 10 V, what is the safe collector current that can be allowed through the transistor?
a) 5 mA
b) 2.5 mA
c) 10 mA
d) 25 mA

Ans: Option a)

29.

The above figure shows the symbol of

a) p channel depletion MOSFET

b) p channel enhancement MOSFET

c) complementary MOSFET

d) p channel JFET

Ans: Option a)

30. Which of the following statements is correct for MOSFETs?

a) p channel MOS is easier to produce than n channel MOS

b) n channel MOS must have twice the area of p channel MOS for the same ON resistance

c) p channel MOS has faster switching action than n channel MOS

d) p channel MOS has higher packing density than n channel MOS

Ans: Option a)

31. The process of extension of a single-crystal surface by growing a film in such a way that the added atoms form a continuation of the single-crystal structure is called

a) Ion implantation

b) Chemical vapour deposition

c) Electroplating

d) Epitaxy

Ans: Option d)

32. The maximum concentration of the element which can be dissolved in solid silicon at a given temperature is termed as

a) Solid Solubility

b) Dissolution coefficient

c) Solidification index

d) Concentration index

Ans: Option a)

33. Which of the following devices is used in the microprocessors?

a) JFET

b) BJT

c) MOSFET

d) CMOS

Ans: Option d)

34. In a CMOS CS amplifier, the active load is obtained by connecting a

a) p channel current mirror circuit

b) n channel transistor

c) p channel transistor

d) BJT current mirror

Ans: Option a)

35. Which of the following is not LED material?

a) GaAs

b) GaP

c) SiC

d) SiO2

Ans: Option d)

36. The minimum energy of a photon required for intrinsic excitation is equal to

a) energy of bottom of conduction band

b) energy of top of valence band

c) forbidden gap energy

d) Fermi level

Ans: Option c)

37. Assertion (A): An unbiased p-n junction develops a built-in-potential at the junction with the n-side positive and the p-side negative

Reason (R): The p-n junction behaves as a battery and supplies current to a resistance connected across its terminals.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option c)

38. Assertion (A): Cut-in voltage for Germanium diode is greater than that for Silicon diode

Reason (R): Germanium diode has a higher reverse saturation current than Silicon diode.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

39. Assertion (A): The h-parameter model of a BJT can be derived from its hybrid -π model and vice-versa.

Reason (R): The hybrid-π model has many more additional elements as compared to h-parameter model of the BJT.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

40. Assertion (A): For same drain current rating N-channel MOSFET occupies more area than -channel MOSFET.

Reason (R): Electron mobility is much higher than hole mobility.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

42. A signal x₁(t) and x₂(t) constitute the real and imaginary parts respectively of a complex valued signal x(t). What form of waveform does x(t) possess?
a) Real Symmetric
b) Complex symmetric
c) Asymmetric
d) Conjugate Symmetric

Ans: Option d)

43. A function of one or more variables which conveys information on the nature of physical phenomenon is called
a) Noise
b) Interference
c) System
d) Signal

Ans: Option d)

44.

Ans: Option a)

45. What is the period of the sinusoidal signal x(n) = 5 cos (0.2 π n)?
a) 10
b) 5
c) 1
d) 0

Ans: Option a)

46.

Ans: Option c)

47.

Ans: Option b)

48. Assertion (A): There are no convergence issues with the discrete-time Fourier series in general.
Reason (R): A discrete-time signal is always obtained by sampling a continuous time signal.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

49. In the field of a charge Q at the origin, the potentials at A(2, 0, 0) and B( 1/2, 0, 0) are Va = 15 volts and Vb= 30 volts respectively. What will be the potential at C( 1, 0, 0 )?

a) 25 volts

b) 22.5 volts

c) 20 volts

d) 17.5 volts

Ans: Option b)

50. What will be the equipotential surfaces for a pair of equal and opposite line charges?

a) Spheres

b) Concentric cylinders

c) Non-concentric cylinders

d) None of the above

Ans: Option c)

51. If the potential functions V1 and V2 satisfy Laplace's equation within a closed region and assume the same values on its surface, then which of the following is correct?

a) V1 and V2 are identical

b) V1 is inversely proportional to V2

c) V1 has the same direction as V2

d) V1 has the same magnitude as V2 but has different direction

Ans: Option a)

52. By what name is the equation ∇. J = 0 frequently known?

a) Poisson's equation

b) Laplace's equation

c) Continuity equation for steady currents

d) Displacement equation

Ans: Option c)

53. Method of images is applicable to which fields?

a) Electrostatic fields only

b) Electrodynamic fields only

c) Neither electrostatic nor electrodynamic fields

d) Both electrostatic and electrodynamic fields

Ans: Option a)

54. Who developed the concept of time varying electric field producing s magnetic field?

a) Gauss

b) Faraday

c) Hertz

d) Maxwell

Ans: Option b)

55.

Ans: Option b)

56. For plane wave propagating in free space or two conductor transmission line, what must be the relationship between the phase velocity Vp, group velocity Vg and speed of light C?

a) Vp > C >Vg

b) Vp < C

c) Vp = C =Vg

d) Vp < Vg < C

Ans: Option a)

57. The reflection coefficient on a 500 m long transmission line has a phase angle of -150 degrees. If the operating wavelength is 150 m, what will be the number of voltage maxima on the line?

a) 0

b) 3

c) 6

d) 7

Ans: Option d)

58. Consider the following statements:

For a 10 m long common power line connecting a switch to a light bulb

i. It is a distributed circuit.

ii. Time delay for propagation through it is negligible.

iii. It is in the form of a shielded coaxial cable of circular cross-section.

iv. As the intensity of the lamp varies, input impedance of this line also changes.

Which of the above statements is/are correct?

a) i only

b) i and ii

c) ii and iii

d) ii and iv

Ans: Option c)

59. With regard to a transmission line, which of the following statements is correct?

a) Any impedance repeats itself every λ/4 on the smith chart.

b) The S.W.R. = 2 circle and the magnitude of reflection coefficient = 0.5 circle coincide on the smith chart.

c) At any point on a transmission line, the current reflection coefficient is the reciprocal of the voltage reflection coefficient.

d) Matching eliminates the reflected wave between the source and the matching device location.

Ans: Option c)

60. It is required to match a 200 Ω load to a 450 Ω transmission line. To reduce the SWR along the line to 1, What must be the characteristic impedance of the quarter-wave transformer used for this purpose, if it is connected directly to the load?

a) 90 kΩ

b) 300 Ω

c) 9/4 Ω

d) 3/2 Ω

Ans: Option b)

61. The load end of a quarter wave transformer gets disconnected thereby causing an open-circuited load. What will be the input impedance of the transformer?

a) Zero

b) Infinite

c) Finite and positive

d) Finite and negative

Ans: Option a)

62. Multiple member of antennas are arranged in arrays in order to enhance what property?

a) Both directivity and bandwidth

b) Only directivity

c) Only bandwidth

d) Neither directivity nor bandwidth

Ans: Option b)

63. Consider the following statements regarding an antenna:

1. It is a transducer.

2. Its performance is essentially frequency sensitive.

3. It is a reciprocal device.

4. With increase in its effective aperture area, width of radiated beam increases.

Which of the above statements are correct?

a) 1,2 and 3

b) 1,2 and 4

c) 2 and 3 only

d) 1 and 4 only

Ans: Option a)

64.What is the minimum value of VSWR that may exist on a transmission line?

a) Less than zero

b) Zero

c) One

d) 10

Ans: Option c)

65. Assertion (A): Capacitance of a solid conducting spherical body of radius 'a' is given by 4πϵ₀a in free space.

Reason (R): ∇ x H = j ϵ 𝛚E + J

a) Both A and R are true and R is the correct explanation of A

b) Both A and R are true but R is NOT the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

66. Assertion (A): The expression E = -∇V, Where E is the electric field and V is the potential is not valid for time varying fields.

Reason (R): The curl of a gradient is identically zero.

a) Both A and R are true and R is the correct explanation of A

b) Both A and R are true but R is NOT the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

67.

a) Both A and R are true and R is the correct explanation of A

b) Both A and R are true but R is NOT the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

68. Assertion (A): As the length of the resonant antenna is increased, the number of lobes increases and the direction of the major lobes is closer and closer to the direction of the dipole.

Reason (R): As the length increases, the current distribution along the wire becomes more and more uniform.

a) Both A and R are true and R is the correct explanation of A

b) Both A and R are true but R is NOT the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option c)

69. For a second order instrument, the optimum range of ξ(damping ratio), which gives good frequency response over a wide range of frequencies is
a) 0.5 to 0.6
b) 0.6 to 0.7
c) 0.7 to 0.8
d) 0.8 to 1.0

Ans: Option a)

70.The wheatstone bridge method of measuring resistance is ideally suited for the measurement of resistance values in the range of
a) 0.001 to 1 Ω
b) 0.1 to 100 Ω
c) 100 Ω to 10 kΩ
d) 100 kΩ to 10 MΩ

Ans: Option c)

71. What is the major cause of creeping in an energy-meter?
a) Over compensation for friction
b) Mechanical vibrations
c) Excessive voltage across the potential coil
d) Stray magnetic fields

Ans: Option a)

72. A compensated wattmeter has its reading corrected for error due to which one of the following parameters?
a) Frequency
b) Friction
c) Power consumed in current coil
d) power consumed in pressure coil

Ans: Option d)

73. Which of the following bridges is also used in an oscillator?
a) Maxwell
b) Schering
c) Hay
d) Wien

Ans: Option d)

74. Which of the following meters cannot measure a.c. quantities?
a) Thermocouple
b) Hot wire
c) P.M.M.C
d) Electrodynamometer

Ans: Option c)

75. Which of the following statements is not correct for thermistors?
a) They have negative temperature coefficient of resistance.
b) The sensing element is made of sintered ceramics, which are oxides of metals in the form of beads.
c) The variation of resistance with temperature is linear.
d) The resistance value at ambient temperature may range from 100 Ωto 100 k Ω.

Ans: Option c)

76. Which of the following devices is used at the first stage of an electronic voltmeter?
a) BJT
b) SCR
c) MOSFET
d) UJT

Ans: Option c)

77. Consider the following statements regarding sources of error in a Q-meter:
1. If a coil resistance R is connected in direct measurement mode and if the residual resistance of Q-meter is 0.1 R, then the measure Q of the coil would be 1.1 time the actual Q.
2. If the inductance to be measured is less than 0.1 mH, the error due to presence of residual inductance cannot be neglected.
3. The presence of distributed capacitance in a coil modifies the effective Q of the coil.
Which of the above statements are correct?
a) 1, 2 and 3
b) 1 and 2 only
c) 2 and 3 only
d) 1 and 3 only

Ans: Option c)

78. What is an advantage of an electronic voltmeter over a non-electronic voltmeter?
a) Low power consumption
b) Low input impedance
c) The ability to measure wide ranges of voltages and resistances
d) Large Portability

Ans: Option a)

79. An average response rectifier type electronic voltmeter has a d.c. voltage of 10 V applied to it. What is the meter reading?
a) 7.1 V
b) 10 V
c) 11.1 V
d) 22.2 V

Ans: Option c)

80. Which one of the following oscillators is used for the generation of high frequencies?
a) R-C phase shift oscillator
b) Wien bridge oscillator
c) L-C oscillator
d) Blocking oscillator

Ans: Option c)

81. Which of the following transducers requires a high input impedance pre-amplifier for proper measurements?
a)Thermocouple
b) Piezoelectric
c) Thermistor
d) L.V.D.T

Ans: Option b)

82. In a digital voltmeter the oscillator frequency is 400 kHz and the ramp voltage falls from 8 V to 0 V in 20 ms. What is the number of pulses counted by the counter?
a) 800
b) 2000
c) 4000
d) 8000

Ans: Option d)

83. Which of the following cannot provide as much time interval accuracy as the oscilloscope but can capture and display eight or more signals simultaneously, something that scopes cannot do?
a) Logical Analyzer
b) Digital Oscilloscope
c) Frequency Analyzer
d) Wave Analyzer

Ans: Option a)

84. Which of the following transducers is most suitable for monitoring continuous variations in very fine thickness of a material?
a) Diaphragm
b) Capacitor
c) L.V.D.T
d) Piezoelectric crystal

Ans: Option b)

85. Consider the following statements about ultrasonic flowmeters:
1. The measurement is insensitive to viscosity, pressure and temperature variations.
2. It has bidirectional measuring capability and can be used for any pipe size.
3. It has a relatively lower cost.
4. It has good accuracy, fast response and wide frequency range.

Which of the above statements is/are correct?
a) 1 only
b) 1 and 2 only
c) 1, 2 and 4
d) 3 and 4 only

Ans: Option c)

86.

Ans: Option b)

87.

Ans: Option c)

88.

Ans: Option c)

89.

Ans: Option c)

90.

Ans: Option d)

91.

Ans: Option b)

92.

Ans: Option a)

93.

Ans: Option b)

94.

Ans: Option b)

95.

Ans: Option d)

96.

Ans: Option b)

97.

Ans: Option a)

98.

Ans: Option c)

99.

Ans: Option a)

100.

Ans: Option b)

101.

Ans: Option a)

102.

Ans: Option c)

103.

Ans: Option d)

104.

Ans: Option a)

105.

Ans: Option c)

106.

Ans: Option d)

107.

Ans: Option d)

108.

Ans: Option a) & c)

109.

Ans: Option c)

110.

Ans: Option b)

PSU MCQs on Electromagnetics

2014-04-15T07:37:00.002+05:30

1. An Antenna that is circularly polarized is the
a) Helical
b) Small circular loop
c) Parabolic reflector
d) Yagi-uda

Ans: Option a)

2. The standard reference antenna for the directive gain is the
a) Infinitesimal dipole
b) Isotropic antenna
c) Elementary doublet
d) Half-wave dipole

Ans: Option b)

3. Top loading is sometimes used with an antenna in order to increase
a) Effective height
b) Bandwidth
c) Beam width
d) Input Capacitance

Ans: Option a)

4. A helical antenna is used for satellite tracking because of its
a) Circular polarization
b) Maneuverability
c) Broad bandwidth
d) Good front-to-back ratio

Ans: Option a)

5. The directivity of an isotropic antenna is
a) Zero
b) Less than unity
c) Unity
d) Infinity

Ans: Option c)

6. In order to receive a vertically polarized wave the conductor of the dipole should be mounted
a) Horizontally
b) Vertically
c) At an angle of 45^o
d) None of these

Ans: Option b)

7. For a dipole antenna
a) The radiation intensity is maximum along the normal to the dipole axis
b) The current distribution along its length is uniform irrespective of the length
c) The effective length equals to its physical length
d) The input impedance is independent of the location of the feed point

Ans: Option a)

8. Two isotropic antennas are separated by a distance of two wavelengths. If both the antennas are fed with currents of equal phase and magnitude, the number of lobes in the radiation pattern in the horizontal plane is
a) 2
b) 4
c) 6
d) 8

Ans: Option d)

9. Consider the following statements:
1.Antenna radiates energy
2. An antenna is a transition device or transducer between a guided wave and free space or vice-versa
3. The resonators and transmission lines store energy
4. An antenna converts electromagnetic signal into current and vice-versa
Which of the following statements are correct?
a) 1,2 and 4 only
b) 1,2 and 3 only

c) 2,3 and 4 only
d) 1,2,3 and 4

Ans: Option a)

10. An antenna can be made more directional by
a) Increasing its diameter
b) Increasing frequency of transmission
c) either a) or b)
d) none of the above

Ans: Option c)

11. The radiation resistance of a circular loop of a turn is 0.01 Ω. The radiation resistance of five turns of such a loop will be
a) 0.002 Ω
b) 0.01 Ω
c) 0.05 Ω
d) 0.25 Ω

Ans: Option c)

12. Far field of an antenna varies with distance r as
a) 1/r
b) 1/r²

c) 1/r³

d) 1/√r

Ans: Option a)

13. Cassegrain feed is used with a parabolic antenna in order to
a) increase the gain of the system
b) Increase the beamwidth of the system
c) Reduce the size of the main reflector
d) Allow the feed to be placed at a convenient point

Ans: Option d)

14. For a plane wave propagating in an unbounded medium (free space), the minimum angle between electric and magnetic field vectors is
a) 0
b) 60
c) 90
d) 180

Ans: Option c)

15. The main difference between the operation of transmission lines and waveguides is that
a) The latter are not distributed, like transmission line
b) The former can use stubs ans quarter-wave transformers, unlike the latter
c) Transmission lines use the principal mode of propagation and therefore do not suffer from low frequency cutoff
d) Terms such as impedance matching and standing wave ratio cannot be applied to waveguides

Ans: Option c)

16. The wavelength of a wave in a waveguide
a) is greater than in free space
b) depends only on the waveguide dimensions and the free space wavelength
c) is inversely proportional to the phase velocity
d) is directly proportional to the group velocity

Ans: Option a)

17. A transmission line whose characteristic impedance is a pure resistance
a) must be a lossless line
b) must be a distortionless line
c) May not be a lossless line
d) May not be a distortionless line

Ans: Option a)

18. A 300 Ω line is terminated in a load impedance of 100 + j 200 Ω. The voltage reflection coefficient is
a) 0.6325 ∟108
b) 0.7 ∟30
c) 0.27 + j 0.196
d) 0.377 ∟42.7

Ans: Option a)

19. Diffraction of electromagnetic waves
a) is caused by reflections from the ground
b) arises only with spherical wavefronts
c) will occur when the wave pass through a large slot
d) will occur around the edge of a sharp obstacle

Ans: Option d)

20. An electromagnetic wave incident on a perfect conductor is
a) Entirely reflected
b) Fully transmitted
c) Partially transmitted
d) None of these
Ans: Option a)

21. Which one of the following sets of equations is independent in maxwell's equations?
a) Two curl equations
b) two divergence equations
c) Both the curl and divergence equations
d) two curl equations combined with the continuity equation

Ans: Option c)

22. Consider the following statements:
For electromagnetic waves propagating in free space:
1. Electric field is perpendicular to direction of propagation
2. Electric field is along the direction of propagation
3. Magnetic field is perpendicular to direction of propagation
4. Magnetic field is along the direction of propagation
Which of these statements are correct?
a) 1 and 3
b) 1 and 4
c) 2 and 3
d) 2 and 4

Ans: Option a)

23. The dominant mode in a rectangular waveguide is TE10 because this mode has
a) No attenuation
b) No cut-off
c) No magnetic field component
d) The highest cut-off wavelength

Ans: Option d)

24. 8-point charges of 1nC each are located at the corners of a cube in free space that on 1m on a side, then at the center is
a) 0 V/m
b) 5 V/m
c) 4 V/m
d) -5 V/m

Ans: Option a)

25. A 50 Ω lossless transmission line has a pure reactance of j100 Ω as its load. The VSWR in the line is
a) 0
b) Infinity
c) 50
d) 100 + j 100

Ans: Option b)

26. Calculate the front-to-back ratio of an antenna in dB which radiates 3 kW in its optimum direction and 500 watts in the opposite direction
a) 0.782
b) 7.782
c) -22.22
d) none of these

Ans: Option b)

27. An uniform plane wave incident normally on a plane surface of dielectric material is reflected with a VSWR of 3. What is the percentage of incident power that is reflected.
a) 10%
b) 25 %
c) 50%
d) 75%

Ans: Option b)

28. Two coaxial cables 1 and 2 are filled with different dielectric constants ϵr1 and ϵr2 respectively. The ratio of the wavelengths in the two cables λ1/ λ2 is
a) √( ϵr1/ ϵr2)
b) √( ϵr2/ ϵr1)
c) ϵr1/ ϵr2
d) ϵr2/ ϵr1

Ans: Option b)

29. Which of the following is zero?
a) Grad div
b) Div grad
c) Curl grad
d) Curl curl

Ans: Option c)

30. Which is not an example of convection current?
a) A moving charged belt
b) Electronic movement in a vacuum tube
c) An electron beam in a television tube
d) Electric current flowing in a copper wire

Ans: Option d)

31. One of the following is not a source of magnetostatic fields
a) A dc current in a wire
b) A Permanent magnet
c) An accelerated charge
d) An Electric filed linearly changing with time

Ans: Option c)

32. Which of thse statements is not characteristic of a static magnetic field?
a) It is solenoidal
b) It is conservative
c) It has no sinks or sources
d) Magnetic flux lines are always closed

Ans: Option b)
Static magnetic field is not conservative

33. Two thin parallel wires carry currents along the same direction. The force experienced by one due to the other is
a) Parallel to the lines
b) Perpendicular to the lines and attractive
c) Perpendicular to the lines and repulsive
d) Zero

Ans: Option b)

PSU MCQs on Satellite Communication and Radar

2014-04-02T18:03:00.002+05:30

1. Most satellites operate in the frequency range of
a) 300 MHz to 3 GHz
b) 30 MHz to 300 MHZ
c) Above 300 GHz
d) 3 GHz to 30 GHz

Ans: Option d)

2. The frequency band used by most satellite is
a) UHF
b) VHF
c) SHF
d) EHF

Ans: Option c)
Super High Frequency: 3 to 30 GHz

3. The bandwidth of a typical satellite is
a) 500 MHz
b) 900 MHz
c) 200 MHz
d) None of these

Ans: Option a)

4. For satellite communication, the frequency should be
a) Less than the critical frequency of ionosphere
b) Equal to the critical frequency of ionosphere
c) More than the critical frequency of ionosphere
d) None of these

Ans: Option c)

5. Geostationary satellites follow
a) circular path
b) elliptical path
c) inclined path
d) cycloidal path

Ans: Option b)

6. A synchronous satellite orbits the earth once in
a) 24 hours
b) 12 hours
c) 6 hours
d) 1 hour

Ans: Option a)

7. The distance of a geostationary satellite from the surface of the earth is nearly
a) 360 Km
b) 3600 Km
c) 36,000 Km
d) 3,60,000 Km

Ans: Option c)

8. Satellite sends back signals to earth by means of
a) Yagi antenna
b) chicken-mesh antenna
c) horn antenna
d) dipole antenna

Ans: Option c)
Satellite sends back signals through horn antenna

9. In satellite communication
a) Amplitude modulation is used
b) Frequency modulation is used
c) Pulse width modulation is used
d) Pulse Amplitude modulation is used

Ans: Option b)

10. Antenna elevation angle at the ground station for satellite communication is always kept above 5^oto
a) minimize the sky noise temperature
b) reduce the effect of oxygen and water vapour absorption on the antenna noise temperature
c) minimize the slant range
d) increase the visibility of the satellite

Ans: Option d)

11. For global communication, the minimum number of satellite needed is
a) one
b) three
c) seven
d) eleven

Ans: Option b)
One satellite can see "one-third" of the globe

12. FM is preferred for satellite communication because
a) satellite channel has large bandwidth and less noise
b) It gives high modulation index
c) low bandwidth is essentially required
d) Other methods of modulation will result in fading and distortion

Ans: Option a)

13. In a satellite system:
a) upward link frequency is half of downward link frequency
b) upward link frequency is greater than that of downward link frequency
c) upward link frequency is lesser than that of downward link frequency
d) upward link frequency is equal to downward link frequency

Ans: Option b)

14. A geostationary satellite
a) remains stationary in space
b) remains at a height of 1000 km above the surface of earth
c) orbits the earth with 24 hour period
d) remains always in a direction opposite to that of sun, with respect to earth

Ans: Option c)

15. Satellite communication links are preferred over sub-marine cables because
a) they are faster
b) they involve lesser cost
c) of their multiple access ability
d) none of these

Ans: Option c)

16. The satellite orbit almost invariably used with remote sensing satellite is:
a) geostationary orbit
b) geosynchronous orbit
c) sun synchronous orbit
d) Molniya orbit

Ans: Option c)

17. The beam width required for a satellite antenna for full global coverage is approximately
a) 1
b) 5
c) 18
d) 4

Ans: Option c)

18. A satellite earth station antenna having a maximum gain of 60 dB at the operational frequency is fed from a power amplifier generating 10 KW. If the feed system has a loss of 2 dB, determine earth station EIRP(Effective Isotropic Radiated Power)

a) 98dBW
b) 100 dBW
c) 89 dB
d) 98 dB

Ans: Option a)

19. A radio communication link is to be established via the ionosphere. The virtual height at the midpoint of the path is 300 km and the critical frequency is 9 MHz. The maximum usable frequency for the link between the stations of distance 800 km assuming flat earth is
a) 11.25 MHz
b) 12 MHz
c) 15 MHz
d) 25.5 MHz

Ans: Option c)

20. If a satellite is launched at an orbital radius of twice that of a geostationary satellite, how much time will the launched satellite take to travel around the earth
a) 48 hrs
b) 12 hrs
c) 96 hrs
d) 6 hrs

Ans: Option c)

T² α r³ by kepler’s law

Since the time period of geostationary satellite is 24 hrs

(T/24)² = 2³

T = 67.88 hrs

20. Which of the following techniques not suitable for automatic satellite tracking?
a) Monopulse
b) Step-track
c) Conical Scanning
d) Lobe switching

Ans: Option b)

21. Which of the following statements is not correct?
a) A geo-synchronous satellite remains practically stationary relative to earth antennas
b) A geo-synchronous satellite means the same thing as geo-stationary satellite
c) There is a trade-off between the cost of a communication satellite and cost of its earth stations
d) Three geo-synchronous satellites cannot give 100% global coverage.
Ans: Option d)

22. Which ionosphere layer is responsible for return of a radiation at frequency 30 MHz?
a) D
b) E
c) F
d) All the above

Ans: Option c)

23. Communication satellites are allotted bandwidth of 500 MHz. This can be increased by using
a) Frequency and Polarization re-use
b) Time division Multiplexing
c) Frequency division Multiplexing
d) Triple modular redundancy

Ans: Option a)

24. What does a link budget for satellite communication include
a) Total cost of satellite
b) Cost of satellite plus launch vehicle
c) Signal and noise levels in dB
d) Margins of error permitted

Ans: Option: c)

25. The output stage of a transponder on-board a satellite has a maximum power output of 10 watts. However, it is not operated at the maximum power output in order to
a) Conserve the available limited battery power
b) Reduce noise due to device
c) Avoid inter-modulation distortion
d) Avoid heating up of the satellite beyond a preset value

Ans: Option a)

RADAR

1) The term RADAR stands for
a) Radio direction and reflection
b) Radio waves dispatching and receiving
c) Random detection and re-radiation
d) Radio detection and ranging

Ans: Option d)

2) Frequency in UHF range propagate by means of
a) Ground waves
b) Sky waves
c) Surface waves
d) Space waves

Ans: Option d)

3) Which of the following diode is used as a detector in a RADAR?
a) Gunn Diode
b) Schottky diode
c) IMPATT diode
d) Any of the above

Ans: Option c)

4) Most of the aircraft surveillance Radars operate in
a) X-band
b) C-band
c) L-band
d) S-band

Ans: Option c)

5) In case of RADAR receiver the IF bandwidth is inversely proportional to
a) Pulse interval
b) Pulse repetition frequency
c) square root of peak transmitted power
d) Pulse width

Ans: Option d)

6) Radar detection is limited to line of sight because
a) Of curvature of the earth
b) The waves are not reflected by the ionosphere
c) Long wavelengths are used
d) Short wavelengths are used

Ans: Option a)

7) To increase the radar range of ground and surface targets to see well beyond the normal radar horizon, the electromagnetic wave propagation adopted is
a) Ionosphere scatter
b) Tropo Scatter
c) Ground wave propagation
d) Duct

Ans: Option b)

8) Troposphere scatter is used with frequencies in the following range
a) HF
b) VHF
c) UHF
d)VLF

Ans: Option c)

9) A Radar receives an echo from a target 20 microseconds after sending the signal. The approximate range of the target is
a) 300 m
b) 3000 m
c) 600 m
d) 6000 m

Ans: Option b)

Range= cT/2 = 3x10⁸ x 20 x 10^-6/2 = 6000/2 = 3000 m

10) Which of the following can be used to improve range resolution in a Radar?
a) Short duration pulse
b) Long duration pulse
c) High frequency of operating signal
d) Increasing bandwidth

Ans: Option a)

11) In a radar system, if the peak transmitted power is increased by a factor of 16 and the antenna diameter is increased by a factor of 2, then the maximum range will increase by a factor of
a) 16
b) 8
c) 4
d) √8

Ans: Option c)

R_max α [ P_t A_e ²]^1/4

R_max α [ P_t D⁴]^1/4

[16 x 16]^1/4=4

12) For identifying a radar target in a non-lossy medium, the range of the target is to be doubled, the RF power radiated must be increased by

a) 2 times

b) 4 times

c) 8 times

d) 16 times

Ans: Option d)

R_max α [ P_t ]^1/4

R_max α [ 16]^1/4

^{13) An Altimeter is basically}

^{a) a CW Radar}

^{b) a FM Radar}

^{c) a Doppler Radar}

^{d) a device to indicate the direction at height}

^{Ans: Option a)}

PSU MCQs on Microwave Engineering

2014-03-29T20:55:00.001+05:30

1. A reflex Klystron fuctions as
a) Microwave oscillator
b) Microwave amplifier
c) Both as Microwave amplifier and oscillator
d) A high gain cavity

Ans: Option a)

2. The modes in a reflex Klystron
a) give the same frequency but different transit times
b) result from excessive transit time across the resonator gap
c) are caused by spurious frequency modulation
d) are just for theoretical considerations

Ans: Option a)

3. Klystron operates on the principle of
a) Amplitude Modulation
b) Frequency Modulation
c) Pulse Modulation
d) Velocity Modulation

And: Option d)

4. In Microwave we take the elements as
a) Lumped circuit elements
b) Distributed circuit elements
c) Both a) and b)
d) None of the above

Ans: Option b)

5. Short term fading in microwave communication links can be overcome by
a) Increasing the transmitted power
b) Changing the antenna
c) Changing the modulation scheme
d) Diversity reception and transmission

Ans: Option d)

6. For handling large microwave power, the best medium is
a) Coaxial line
b) Rectangular waveguide
c) Stripline
d) Circular waveguide

Ans: Option b)

7. A Microwave tube amplifier uses an axial magnetic field and radial electric field. This is the
a) Reflex Klystron
b) Coaxial Magnetron
c) Travelling wave magnetron
d) CFA-Crossed Field Amplifier

Ans: Option d)

8. A disadvantage of microstrips with respect to stripline circuit is that the former:
a) Do not let themselves to be printed-circuits
b) Are more likely to radiate
c) Are bulkier
d) Are more expensive and complex to manufacture

Ans: Option d)

9. Most of the power measuring microwave devices measure
a) Average power
b) Peak power
c) Instantaneous power
d) None of these

Ans: Option a)

10. HEMT used in microwave circuit is a
a) Source
b) High power amplifier
c) Detector
d) Low noise Amplifier

Ans: Option d)

11. Ionospheric preparation is not possible for microwaves because
a) Microwaves will be fully absorbed by the ionospheric layers
b) There will be an abrupt scattering in all directions
c) Microwave will penetrate through the ionospheric layers
d) There will be dispersion of microwave energy

Ans: Option c)

12. A waveguide section in a microwave circuit will act as a
a) Low-pass filter
b) Band-pass filter
c) High-pass filter
d) Band-reject filter

Ans: Option c)

13. The biggest advantage of the TRAPATT diode over the IMPATT diode is its
a) Low noise
b) Higher efficiency
c) Ability to operate at higher frequencies
d) Lesser sensitivity to harmonics

Ans: Option b)

14. A varactor diode may not be useful at microwave frequencies
a) For electronic tuning
b) for frequency multiplication
c) as an oscillator
d) As a parametric amplifier

Ans: Option c)

15. The negative resistance in a tunnel diode
a) is maximum at the peak point of the characteristic
b) is available between the peak and valley points
c) is maximum at valley point
d) may be improved by the use of reverse bias

Ans: Option b)

16. Which one of the following is a transferred electron device?
a) BARITT diode
b) IMPATT diode
c) Gunn diode
d) Step recovery diode

Ans: Option c)

17. A PIN diode is suitable for use as a
a) Microwave switch
b) Microwave mixed diode
c) Microwave detector
d) None of these

Ans: Option a)

18. The semiconductor diode which can be used in switching circuits at microwave range is
a) PIN diode
b) Tunnel diode
c) Varactor diode
d) Gunn diode

Ans: Option a)

19. Microwave antenna aperture efficiency depends on
a) Feed Pattern
b) Antenna Aperture
c) Surface losses
d) Low side lobe level

Ans: Option b)

20. The noise produced in a microwave tube due to random nature of emission and electron flow is called
a) Partition noise
b) Shot noise
c) Johnson noise
d) Shannon noise

Ans: Option b)

21. A duplexer is used
a) To couple two different antennas to a transmitter without mutual interference
b) To allow one antenna to be used for reception or transmission without mutual interference
c) To prevent interference between two antennas when they are connected to a receiver
d) To increase the speed of the pulses in pulsed radar

Ans: Option b)

22. One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their
a) Noise figure increases
b) Transit time becomes too short
c) Shunt capacitive reactances become too large
d) Series inductive reactances become too small

Ans: Option a)

23.A magic-Tee is nothing but
a) A modification of E-plane tee
b) A modification of H-plane tee
c) A combination of E-Plane and H-Plane
d) Two E-plane tees connected in parallel

Ans: Option c)

24. Which of the following can be used for amplification of microwave energy?
a) Travelling wave tube
b) Magnetron
c) Reflex Klystron
d) Gunn diode

Ans: Option a)

25. In microwave power measurements using bolometer, the principle of working is the variation of
a) Inductance with absorption of power
b) Resistance with absorption of power
c) Capacitance with absorption of power
d) Cavity dimensions with heat generated by the power

Ans: Option b)

26. In π mode operation of magnetron, the spokes due to phase focusing effect rotate at an angular velocity corresponding to
a) One pole/cycle
b) Two poles/cycle
c) Four poles/cycle
d) Six poles/cycle

Ans: Option b)

27. For Gunn diodes, gallium arsenide is preferred to silicon because the former
a) Has a suitable empty energy band, which silicon does not have
b) Has a higher ion mobility
c) Has a lower noise at the highest frequencies
d) Is capable of handling higher power densities

Ans: Option a)

28. For best low-level noise performance in the X-band an amplifier should use
a) A bipolar transistor
b) A Gunn diode
c) A step recovery diode
d) An IMPATT diode

Ans: Option c)

29. Travelling wave parametric amplifiers are used to
a) provide a greater gain
b) reduce the number of varactor diodes required
c) avoid the need for cooling
d) provide a greater bandwidth

Ans: Option d)

30. The major advantage of TWT over Klystron
a) higher gain
b) higher frequency
c) higher output
d) higher bandwidth

Ans: Option d)

31. Microwave frequency range extends from
a) 3 MHz to 30 MHz
b) 30 MHz to 300 MHz
c) 300 MHz to 3000 MHz
d) 500 MHz to 30000 MHz

Ans: Option d)

32. Due to curvature of earth, microwave repeaters are placed at a distance of about
a) 10 Km
b) 50 Km
c) 150 Km
d) 250 Km

Ans: Option b)

33. At microwave frequencies the size of the antenna becomes
a) Very large
b) Large
c) Small
d) Very Small

Ans: Option d)

34. Which of the following noise becomes important at microwave frequencies
a) Shot noise
b) Flicker noise
c) Thermal noise
d) Transit time noise

Ans: Option d)

35. The phenomenon of microwave signals following the curvature of earth is known as
a) Faraday effect
b) Ducting
c) Wave tilt
d) Troposcatter

Ans: Option b)

36. The front end of an amplifier chain in manufacture of a communication system is kept immersed in liquid nitrogen to
a) Dissipate heat generated by amplifier
b) Expand the frequency response
c) Improve its noise figure
d) reduce the distortion by the amplifier

Ans: Option c)

37. In microwave communication links, the rain drop attenuation experienced is mainly due to
a) Absorption of microwave energy by water vapour
b) resonance absorption of atomic vibration in water molecules
c) scattering of microwaves by collection of water drops
d) refraction of microwaves through liquid-drop lenses formed by rain

Ans: Option a)

PSU MCQs on Microprocessors

2014-03-27T21:10:00.002+05:30

1. A memory system has a total of 8 memory chips, each with 12 address lines and 4 data lines. The total size of the memory system is
a) 16 Kbytes
b) 48 Kbytes
c) 32 Kbytes
d) 64 Kbytes

Ans: Option a)
Each chip has 2¹² = 4096 x 4 bits
Capacity of 8 chips = 4096 x 4 x 8 = 16 Kbytes

2. What will be the size of memory address space for a 16 bit data and 20 bit address bus?
a) 1 MB
b) 64 KB
c) 2 MB
d) None of these

Ans: Option a)

Size of memory address space depends on the address bus size.
2²⁰ = 1048576 = 1 MB

3. The memory address of last location of an 8 KB memory chip is FFFF H. Find the starting address.
a) F000 H
b) E001 H
c) E000 H
d) F001 H
Ans: Option c)

4. A microprocessor is capable of addressing 64 K bytes of memory. Its address bus width is
a) 8
b) 16
c) 12
d) 20

Ans: Option b)
64 K = 2ⁿ

64 x 1024 = 2ⁿ

2⁶ x 2¹⁰ = 2¹⁶

5. How many address lines are necessary to address 2 MB of memory?

a) 21

b) 20

c) 22

d) 10

Ans: Option a)

6. How many memory cells are there in a 128 x 4 memory chip?
a) 128
b) 512
c) 4
d) 1024

Ans: Option b)

7. An 8-bit microprocessor signifies that it has
a) An 8-bit address bus
b) An 8 bit controller
c) 8-bit interrupt lines
d) An 8 bit data bus

Ans: Option d)

8. In a microprocessor based system, the stack is always in
a) Microprocessor
b) ROM
c) RAM
d) EPROM

Ans: Option c)

9. Which of the following statements is false?
a) A microprocessor has bi-directional address bus
b) A microprocessor has a unidirectional address bus
c) A microprocessor has bidirectional data bus
d) A microprocessor has an ALU

Ans: Option b)

10. A stack is
a) An 8 bit register in the microprocessor
b) An 16 bit register in the microprocessor
c) A set of memory locations in R/W memory reserved for storing information
d) An 16 bit memory address stored in the PC

Ans: Option c)

11. When a sub routine is called, the address of instruction following the CALL instruction is stored in/on the
a) Stack Pointer
b) Accumulator
c) Program Counter
d) Stack

Ans: Option c)

12. The stack operates as
a) FIFO
b) LILO
c) LIFO
d) None of these

Ans: Option c)

13. The data bus of any microprocessor is always
a) Unidirectional
b) bi-directional
c) Either unidirectional or bi-directional
d) None of these

Ans: Option b)

14. Which one of the following is not a vectored interrupt?
a) TRAP
b) RST 7.5
c) INTR
d) RST3

Ans: Option a)

15. Identify the non-maskable interrupt from the following
a) RST 7.5
b) RST 5.5
c) RST 6.5
d) RST 4.5

Ans: Option d)
Except TRAP( RST 4.5), all other interrupts are maskable

16. The number of hardware interrupts present in 8085 microprocessor are
a) 5
b) 10
c) 8
d) 16

Ans: Option a)

TRAP
RST 7.5
RST 6.5
RST 5.5
INTR

17. An instruction which contains the data in it uses
a) Register Addressing
b) Immediate Addressing
c) Register Indirect Addressing
d) Relative addressing

Ans: Option b)

18. The clock frequency of 8085 microprocessor is
a) 2 MHz
b) 3 MHz
c) 4 MHz
d) 6 MHz

Ans: Option b)

19. The crystal frequency of 8085 microprocessor is
a) 2 MHz
b) 3 MHz
c) 4 MHz
d) 6 MHz

Ans: Option d)

20. The addressing mode used in the instruction PUSH B is
a) direct
b) register
c) register indirect
d) Immediate

Ans: Option c)

21. When any arithmetic instruction such as ADD or SUB is executed the condition flags
a) are always set
b) are always reset
c) are not affected
d) are affected indicating specific conditions

Ans: Option d)

22. When any data transfer instruction, for transfer of data between memory and microprocessor, is executed the condition flags are
a) not affected
b) always set
c) always reset
d) affected indicating specific conditions

Ans: Option a)

23. Which of the following flag condition are not available in 8085 microprocessor?
a) Zero Flag
b) Parity Flag
c) Overflow Flag
d) Auxillary Flag

Ans: Option c)

24. Which of the following instruction will never affect the zero flag?
a) DCR reg.
b) ORA reg.
c) DCX reg.
d) XRA reg.

Ans: Option c)

25. In a flag register of 8085, where does the sign flag and parity flag set?
a) D₇ and D₆

b) D₆ and D₄

c) D₇ and D₂

d) D₇ and D₄

Ans: Option c)

26. Specify the number of times the given loop will count

LOOP: MVI B, 64 H
DCR B
JNZ LOOP
a) 101
b) 100
c) 65
d) infinite

Ans: Option d)

27. If the result has an odd number of 1s, what will happen to the parity flag
a) Set
b) Reset
c) Data insufficient
d) None of these

Ans: Option b)

28. The instruction RST 7 is a
a) Restart instruction that begins the execution of a program
b) One-byte call to the memory address 0038 H
c) One-byte call to the memory address 0007 H
d) Hardware interrupt

Ans: Option b)

29. Which of the following instruction can be set to clear CY flag?
a) XRA A
b) CLR
c) AND A
d) ADD A

Ans: Option a)

30. The number of status flags present in 8085 microprocessor are
a) 8
b) 5
c) 16
d) 10

Ans: Option b)

31. Let the contents of register C be 00000000 before DCR C is executed. The contents of the register after the execution of this instruction will be
a) 00000000
b) 00000001
c) 11111111
d) None

Ans: Option c)

32. PUSH B instruction in 8085 microprocessor causes
a) the contents of register B only to be copied in the stack
b) the contents of register B and C to be copied in the stack
c) the contents of register B and C to be transferred in the stack and the registers get cleared
d) Registers B and C to be cleared

Ans: Option b)

33. How many times the following loop will be executed?

LXI B, 0007 H

LOOP: DCX B

MOV A, B

ORA C

JNZ LOOP

a) 7 times

b) Cant say

c) 8 times

d) infinitely

Ans: Option a)

34. The multiplexing of address bus and data buses is used in microprocessors

a) To reduce the hardware complexity

b) To increase the number of pins

c) To reduce the number of pins on IC

d) To improve the operation

Ans: Option c)

35. In a 8085 microprocessor based system, the contents of SP are 1000 H. PUSH B instruction will transfer the contents of registers B and C respectively for memory locations

a) OFFF H and OFFE H

b) 1000 H and 0FFF H

c) OFFE H and OFFFH

d) 1000 H and 1001 H

Ans: Option a)

36. Intel 8085 is an
a) 8 bit NMOS processor
b) 8 bit CMOS processor
c) 8 bit PMOS processor
d) 8 bit HMOS processor

Ans: Option a)

37. Which of the following is a 3 byte instruction?
a) LDA 2050 H
b) MVI A, 32 H
c) MOV C, A
d) ADD B

Ans: Option a)

38. Which of the following devices is commonly used to interface O/P devices?
a) Latch
b) Tristate buffer
c) Both a) and b)
d) None of these

Ans: Option a)

39. Which of the following devices is commonly used to interface I/P devices?
a) Latch
b) Tristate buffer
c) Both a) and b)
d) None of these

Ans: Option b)

40. Specify the flag status (CY, S, Z) after the execution of instruction DRA.

MVI A, A9 H

MVI B, 57 H

ADD B

ORA A

a) 1,1,1

b) 0,1,0

c) 1,0,1

d) 1,1,0

Ans: Option a)

41. Wait states are used
a) to give slow devices additional time to put out valid data
b) to insert deliberate delay
c) during I/O operation
d) none of the above

Ans: Option a)

42. READY signal in 8085 is useful when the CPU communicates with
a) a slow peripheral device
b) a fast peripheral device
c) a DMA controller chi
d) A PPI chip

Ans: Option a)

43. Direct-Memory-Access Channel (DMA) facilitates data to move into and out of system
a) on first-come-first-serve basis
b) with equal time delay
c) with sub-routine
d) without program intervention

Ans: Option d)

44. Return from subroutine is affected by
a) a jump instruction
b) an RST instruction
c) a RET instruction
d) a hardware interrupt signal

Ans: Option c)

45. In a generic microprocessor instruction cycle time is
a) shorter than machine cycle time
b) larger than machine cycle time
c) exactly double the machine cycle time
d) exactly the same as the machine cycle time

Ans: Option d)

46. The highest priority interrupt in 8085 microprocessor system is
a) RST 7.5
b) RST 6.5
c) INTR
d) TRAP

Ans: Option d)

47. Which of the following statements is not applicable to serial transmission of data?
a) one bit at a time
b) faster method of transmission
c) LSB transferred first
d) only one wire used

Ans: Option b)

48. The three buses associated with three-bus system are I/O bus, memory bus and
a) address bus
b) unibus
c) direct memory access bus
d) data bus

Ans: Option c)

49. The bus which is used to transfer data from main memory to peripheral device is
a) data bus
b) input bus
c) DMA bus
d) output bus

Ans: Option c)

50. SHIFT LEFT instruction causes all bits shifted from one position to the left with rightmost bit set to zero. The effect is to
a) multiply by 2
b) divide by 2
c) SET the most significant bit
d) none of the above

Ans: Option a)

51. Which of the following signal is used when a peripheral device request the microprocessor to have a DMA operation?

a) IO/M
b) READY
c) HOLD and HLDA
d) RD and WR

Ans: Option c)

52. The output data lines of microprocessors and memories are usually tri-stated, because
a) More than one device can transmit information over the data bus by enabling only one device
b) More than one device can transmit information over the data bus at the same time
c) The data lines can be multiplexed for both input and output
d) It increases the speed of data transfers over the data bus

Ans: Option a)

53. Which of the following instruction copies a byte of data into the accumulator from the memory address given in the instruction?
a) LDA address
b) LDAX B
c) LHLD address
d) STA address

Ans: Option a)

ISRO EC 2006 SET B

2014-03-17T23:10:00.003+05:30

Sol: Option c)

Taking the characteristic equation

Another Method:

Sol: option C)

Sol: Option a)

Sol: Option b)
At resonance

Sol: Option d)
In a series RLC circuit:
Below resonance frequency, circuit has capacitive impedance
At resonance, circuit impedance is totally resistive
Above resonance, circuit has inductive impedance

Sol: Option d)

Sol: Option a)
In Sigma delta ADC, high bit accuracy is achieved by Over Sampling and noise shaping.

Sol: Option a)

Sol: Option b) or d)

Sol: option a)

Sol: Option a)

Sol: Option a)

Sol: Option c)

Sol: Option a)

Sol: Option c)

Sol: Option d) with small correction in last but first term. It should be (Xn-2)(Xn-1) '+' sign should be removed in between .

Sol: Option a)

Sol: Option b)

Sol: Option a)

Sol: Option b)

Sol: Option d)

Sol: Option c)

Sol: Option b)

Sol: Option d)

Sol: Option c)

Sol: Option d)

Sol: Option a)

Sol: Option b)

Sol: Option c)
No possible grouping.

Sol: None of the options. It is actually gray to binary converter.

Sol: Option a)

Sol: Option d)

Sol: Option b)

Sol: Option d)

Sol: Option a)

Sol: Option d)

Sol: Option c)

Sol: Option b)

Sol: Option b)

Sol: Option d)

Sol: Option b)

Sol: Option a)

Sol: Option c)

Sol: Option d)

Sol: Option c)

Sol: Option b)

Sol: option b)

Sol: Option d)

Sol: Option a)

Sol: Option b)

Sol: Option c)

Sol: Option d)

Sol: Option c)
Hysteresis loss and Eddy current loss depends on frequency.

Sol: Option c)

Sol: Option a)

Sol: Option d)
A Capacitor blocks dc voltage. Therefore its zero steady state current.

Sol: Option b)

Sol: Option d)

Sol: Option a)

Sol: option d)

Sol: Option d)

ISRO 2011 ECE Answers

2013-05-06T19:11:00.002+05:30

ISRO 2011 EC SET A

1. In an amplitude modulated system if the total power is 600 W and the power in the carrier is 400W, the modulation index is
a. 0.5
b. 0.75
c. 0.9
d. 1
Solution:

P_{Side band}= P_Total – P_carrier

P_{Side
band = 600 - 400 = 200 W}

P_S / P_{T = 200/600 = 1/3}

Solving we get µ = 1

Answer: Option d

2. The channel capacity under the Gaussian noise environment for a discrete memoryless channel with a bandwidth of 4 MHz and SNR 31 is
a. 20 Mbps
b. 4 Mbps
c. 8 Kbps
d. 4 Kbps

Solution:

Channel capacity = C=B log₂(1+ SNR)

= 4 M log₂(1+31)

= 4 M x 5 = 20 Mbps

Answer: Option: a

3. In satellite communication, frequency modulation is used because satellite channel has
a. High Modulation index
b. Small bandwith and negligible noise
c. Large bandwidth and severe noise
d. Maximum Bandwidth and Minimum noise
Answer: Option d
4. For a 3-µm diameter optical fiber with core and cladding indexes of refraction of 1.545 and 1.510 respectively. The cut off wavelength is
a. 2.3 µm
b. 1.29 µm
c. 1.5 µm
d. 3.24 µm
Solution:

= 1.2808 µm

Answer: option b

5. A 12 bit ADC is operating with a 1 µs clock period and total conversion time is seen to be 14 µs always. The ADC must be of the type

a) Flash

b) Counting type

c) Integrating type

d) Successive Approximation type

Answer: option d

Solution:

Answer: Option b

A Process contains only sequential statements.
Answer : option b

2¹² = 4096 bytes = 4Kbytes

Answer: option d

A resistance in parallel with an indeal current source.

Answer: Option b

The dominant mode has lowest cutoff frequency and hence highest cutoff wavelength.
Answer: Option d

The reverse recovery time involves a diode switching from FB to RB. Reverse recovery time will be of several microseconds. Therefore at t=0, the diode would not have recovered from forward bias condition. Hence current will be same as 100 mA.
Answer: Option d

Aswer: option d

Thread: the primitive that can execute code. It contains an Instruction pointer and sometimes has its own stack.
Process: An environment in which one or several threads run.
Kernel: Run time OS- takes care of thread scheduling.
Answer: Option d

Answer: Option c

Total frequency = 3.6k + 3 x (1.2k) = 7.2kHz

Sampling frequency = 2 x 7.2 k = 14.4 Khz

Answer: Option b

An Addition of 6-dB improvement in SNR is obtained for each bit added to the PCM word.

6.02 x n = 6.02 x 2 = 12.04 = increase by 12 dB

Answer: Option b

QPSK is mostly used in digital data.

Answer: option d

Answer: Option a

Clock	J	K	Qn	Q’n	Qn+1	Q’n+1
0^th clock	0	1	0	1	1	0
1^st clock	1	1	1	0	0	1
2^nd clock	0	1	0	1	1	0
3^rd clock	1	1	1	0	0	1
4^th clock	0	1	0	1	1	0
5^th clock	1	1	1	0	0	1

The ouput toggles when J=K=1.
Answer: Option d

Answer: Option c

Answer: Option d

An instruction cycle has one or more machine cycles.

Instruction > Machine

Machine cycle time period is shorter than instruction cycle time period .

Answer: option c

Pnew = 2000 W

Answer: Option d

Answer: Option a

Answer: Option c

Pre-emption : The ability of the operating sytem to pre-empt or stop a currently scheduled task in favour of a higher priority task.

Answer: Option c

Answer: Option a

1200k + 2(450k) = 1200 + 900 = 2100kHz

Answer: Option d

Answer: Option c

Answer: option d

Answer: Option b

Answer: Option c

Anwer: Option b

First 3 choices are wrt I/o mapped I/o

Answer: Option d

Answer: Option a

Answer: Option b

Answer: Option c

Answer: Option a

Answer: Option b

Answer: Option c

Answer: Option b

Answer: Option C

Answer: Option b

Answer: Option c

Answer: Option a

Answer: Option d

Answer: Option c

Answer: Option a

Answer: Option d

Answer: Option b

Answer: Option a

Answer: Option c

Answer: Option a

Answer: Option b

Answer: Option d

Answer: Option a

Answer: Option d

Answer: Option a

Answer: Option c

Answer: Option b

Answer: Option c

Answer: Option b

Answer: Option c

Answer: Option a

Answer: Option b

Answer: Option a

Answer: Option c

Answer: Option d

Answer: Option b

Useful Formula's - Semiconductor devices

2011-07-04T20:50:00.000+05:30

FAQs

2011-04-12T14:18:00.000+05:30

1. What is a) Current b)Voltage c) Resistance?
Ans: a) Flow of electric charge in a medium b)Energy carried by the charge c) Force that opposes the flow of electric charge
2. What are active and passive elements?
Ans: Active elements are capable of delivering power, while passive elements are capable of receiving, and possibly storing, power.
3. What is the difference between ac and dc current?
Ans: In DC(Direct current), the electrons flow steadily in a single direction, or "forward." In AC (Alternating Current), electrons keep switching directions, sometimes going "forwards" and then going "backwards."
4. What is a Spectrum?
Ans: Range of all possible frequencies of electromagnetic radiation.
5. What is a filter?
Ans: A circuit designed to selectively filter a frequency or a range of frequencies is called a filter.
6. What is dependent and independent source?
Ans: A dependent source maintains an output (fixed or varying with time) which is affected by any other quantity.
An independent source maintains an output (fixed or varying with time) which is not affected by any other quantity.
7. What is Power and What is its relation to Current and voltage?
8. What is the difference between voltage and induced e.m.f.?
9. What is a) Ohms law b) KVL
c) KCL d) Thevenins Theorem
e) Nortons Theorem f) Superposition Theorem?
Ans:
a) Ohms law states that the voltage is directly proportional to current, the proportionality constant being resistance. (V= I.R)
b) KVL states that the algebraic sum of the voltages between successive nodes in a closed path in a circuit is equal to zero.
c) KCL states that the algebraic sum of the currents in all the branches that converge in a common node is equal to zero.
10. What is the difference between series and parallel connection?
11. What is resistivity?
Ans: Resistivity = (Resistance x Cross-sectional area)/ Length

ρ = R.A/L

Electronics and Communication Engineering Reference Books

2011-03-17T21:35:00.000+05:30

Networks:

Network Analysis VanValkenburg
Engineering Circuit Analysis Hayt & Kemmerly
Electric Circuits by Joseph A. Edminister
Fundamentals of Electric Circuits – Sadiku

Electronic devices:

Integrated electronics by Milman Halkias
Electronic Principals by Malvino
Micro Electronic Circuits by Sedra & Smith
Electronic Devices and Circuits by David A Bell
Electronic Devices And Circuits by Boylestead
Solid State Electronic Devices by Benjamin G Streetman

Analog Circuits:

Integrated Electronics by Millman and Halkias
Electronic devices and circuits by Boylestad and Nashelsky
Electronic devices and circuits by Millman and Halkias
Microelectronics by Millman and Grabel
Analog Circuits by Sedra and smith
Linear ICs and integrated circuits by Gaekwad

Signals and Systems:

Signal and Systems Simon Haykin
DSP by Proakis and Manolkis
Signals and Systems by Oppenheim and Schaffer
Signals and systems by B.P.Lathi

Digital Circuits:

Digital Electronics by Morris Mano
Microprocessor by Ramesh Gaonkar
Digital Principles and Design by Donald Givone
Digital Circuits by Taub and Shilling
Digital Electronics by Salivahanan

Electromagnetics:

Engineering Electromagnetics by William Hayt
Elements of Electromagnetics by Mathew Sadiku
Electromagnetic waves and Radiating system by Jordan and Balmein
Electromagnetics by K.D.Prasad
Microwave devices and circuits by Liao
Schaum Series for solved problems

Communications:

Communication System by Simon Haykin
Principles of Communication system by Taub and Schilling
Schaum series for solved problems
Modern and Digital Communication system by B.P. Lathi

MIT Lectures on Single variable Calculus

2011-03-14T20:06:00.000+05:30

Lecture 1:
Definition of Derivative

Lecture 2:
Limits and Continuity

Lecture 3:
Derivatives

Lecture 4:
Chain Rule

Lecture 5:
Implicit Differentiation

Lecture 6:
Exponential and Log

Lecture 7:
Hyperbolic Functions

Lecture 9:
Linear and Quadratic Approximations

Lecture 10:
Curve Sketching

Lecture 11:
Max-Min

Lecture 12:
Related-Rates

Lecture 13:
Newtons-Method

Lecture 14:
Mean-Value Theorem

Formula's- Basic electronics

2011-03-13T13:53:00.000+05:30

Ohm's Law:
For Resistance:(R)ohms
V = I.R Volts
R = V/I Ohms
I = V/R Amperes

For Inductance:

V = L.(di/dt)

For Capacitor:
I = C.(dv/dt)

Lead out Loud

2011-03-13T11:56:00.000+05:30