Electrical MCQ

Power Electronics MCQ #17

2019-09-01T22:19:00.000-07:00

1) The middle region of transistor is called _____.

(a) Emitter

(b) Base

(c) Collector

(d) diffusion

2) When the PN junction diode is under forward biased condition, increasing the battery voltage is results ________.

(a) the current through PN junction remains constant.

(b) the current flow through the junction is zero.

(c) the current through PN junction is decreased.

(d) increasing the current through PN junction.

3) In half wave rectifier, ______ number of diode/s needed.

(a) one

(b) two

(c) eight

(d) four

4) Which of the following material has a resistance between the insulator and conductor?

(a) conductors

(b) insulators

(c) semiconductor materials

(d) none of the above

ANSWER: | 1-b | 2-d | 3-a | 4-c |

5) Purest form of the semiconductor form is known as______.

(a) extrinsic semiconductors

(b) intrinsic semiconductors

(c) combinations of A and B

(d) trivalent substance

6) By adding impurity, the conductivity of semiconductor increased is known as _____.

(a) doping

(b) increase energy gap

(c) increase forbidden gap

(d) reduced energy gap

7) The doped semiconductors are known as ______.

(a) electrons majority carries

(b) extrinsic semiconductor

(c) intrinsic semiconductor

(d) holes majority carries

8) In intrinsic semiconductor, the number of holes is ______.

(a) equal to number of electrons

(b) greater than number electrons

(c) less than number electrons

(d) none of the above

ANSWER: | 5-b | 6-a | 7-b | 8-a |

9) The forbidden energy gap of silicon is ____and for germanium is ____.

(a) 1.1 eV; 1.1 eV

(b) 0.72 eV; 1.1 eV

(c) 0.72 eV; 0.72 eV

(d) 1.1 eV; 0.72 eV

10) In semiconductor, the highest filled band is known as _____ band.

(a) forbidden gap

(b) conduction

(c) valance

(d) none of the above

11) By which region the conduction band and valence band are separated?

(a) forbidden energy gap

(b) conduction band

(c) valance band

(d) none of the above

12) Which of the following band has highest energy level?

(a) forbidden energy band

(b) valance band

(c) energy band

(d) conduction band

ANSWER: | 9-d | 10-c | 11-a | 12-d |

Electrical Machine MCQ #18

2019-08-28T00:01:00.000-07:00

1) In synchronous generator, to reduce hysteresis loss the stator core is assembled with

(a) low grade silicon steel

(b) high grade silicon steel

(c) laminated core

(d) cast iron

2) In case of 4-pole machine, how many cycles of emf is generated in one complete revolution of rotation?

(a) one cycle

(b) two cycles

(c) three cycles

(d) four cycles

3) Which equation gives the relation between electrical degree and mechanical degree?

(a) Electrical degree = P/6 x mechanical degree

(b) Electrical degree = P/4 x mechanical degree

(c) Electrical degree = P/2 x mechanical degree

(d) Electrical degree = P x mechanical degree

4) For a 2-pole machine, 360° of electrical cycle is equal _______ of mechanical rotation?

(a) 90°

(b) 180°

(c) 270°

(d) 360°

ANSWER: | 1-b | 2-b | 3-c | 4-d |

5) The pole pitch is defined as _____.

(a) It is the peripheral distance between the two adjacent poles

(b) The periphery of the armature divided by the number of poles

(c) Both A and B

(d) It is the distance between the two coil sides

6) Why the starters are used in the induction motor?

(a) to provide under voltage protection

(b) to reduce the heavy starting current

(c) to provide over load protection

(d) all of the above

7) Which starters commonly used for the cage type induction motors?

(a) Autotransformer

(b) star-delta starter

(c) direct online starter

(d) all of the above

8) A star-delta starter is used for _____, designed to run normally on _____ winding.

(a) cage rotor motor; delta connected rotor

(b) wound rotor motor; delta connected stator

(c) cage rotor motor; delta connected stator

(d) wound rotor motor; delta connected rotor

ANSWER: | 5-c | 6-d | 7-d | 8-c |

9) In autotransformer starter the starting current is limited to reduced

(a) the initial stator currents

(b) the field current

(c) the initial load currents

(d) the initial stator voltage applied

10) A star delta starter is

(a) commonly used for small and medium size motors

(b) cheaper than auto transformer

(c) Both A and B

(d) costly than autotransformer

11) Which test is performed to calculate the efficiency of the motors?

(a) no-load test

(b) blocked rotor test

(c) regenerative test

(d) Both A and B

12) which test is performed to calculate friction and windage loss?

(a) blocked rotor test

(b) open circuit test

(c) regenerative test

(d) any of the above

ANSWER: | 9-d | 10-c | 11-d | 12-b |

Basic Electrical MCQ #20

2019-08-06T22:27:00.002-07:00

1) A thermo-couple device

a) has low time constant when it is bare.

b) has same time with or without sheath.

c) has low time constant when the sheath is provided.

d) none of the above.

2) A null type instruments has ______ compared to the deflection type instruments.

a) fast response

b) less sensitivity

c) high accuracy

d) a and b both

3) The dynamic characteristic of capacitive transducer is similar as _____.

a) high pass filter

b) low pass filter

c) band stop filter

d) notch filter

4) In HRC fuses, which material is used to fill the space within the body surrounding the element?

a) Zinc

b) Silver

c) Copper

d) Quartz

ANSWER: | 1-a | 2-c | 3-a | 4-d |

5) Candela is the unit of which quantity?

a) Luminous intensity

b) Wavelength

c) Frequency

d) Luminous flux

6) Which lamps can be directly connected to a solar cell?

a) Incandescent

b) Metal Halide

c) Compact Fluorescent

d) LED

7) Which type of photoelectric transducers is used to generate the electrical energy from the solar energy?

a) Photo voltaic cell

b) Photo diode

c) Photo transistor

d) Photo emission cell

8) The value of resistance of earthing electrode depends on ______.

a) shape and material of the electrode

b) specific resistance of the soil

c) depth of which electrode is driven into earth

d) all of the above

ANSWER: | 5-a | 6-d | 7-a | 8-d |

9) A transformer transforms

a) voltage

b) current

c) voltage and current

d) power

10) Which quantity is remains constant in the transformer?

a) voltage

b) current

c) frequency

d) frequency and voltage

11) CT is used for measuring

a) Voltage

b) Frequency

c) Power factor

d) Alternating current

12) The following is Y class insulating material:

a) Mica

b) Cotton

c) Porcelain

d) Asbestos

ANSWER: | 9-c | 10-c | 11-d | 12-b |

Power Electronics MCQ #16

2019-08-02T00:53:00.001-07:00

1) Which device is used to convert DC power into AC power?

a) Inverter

b) Rectifier

c) Transformer

d) Amplifier

2) _____ is defined as the ratio of RMS value of the AC component in the output to the average or DC component represent in the output.

a) Transformer Utilisation Factor (TUF)

b) Ripple Factor

c) Diversity Factor

d) Demand Factor

3) The circuit which is used to remove unwanted portion of the waveform, without distorting the remaining part of the waveform are called _____.

a) Clippers circuit

b) Clamper circuit

c) Voltage doubler circuit

d) Voltage tripler circuit

4) The circuit which is used to add a DC level as per the requirements to the AC output signal are called ______.

a) Clippers circuit

b) Clamper circuit

c) Voltage doubler circuit

d) Voltage tripler circuit

ANSWER: | 1-a | 2-b | 3-a | 4-b |

5) In NPN transistor, the emitter current (I_E) = _______

a) IB + IC

b) IB – IC

c) IC – IB

d) IB

6) In which region transistor works as an amplifier?

a) Saturation region

b) Cut-off region

c) Active region

d) None of the above

7) SCR has ____ junctions and _____ terminals.

a) 2, 3

b) 3, 3

c) 3, 2

d) 2, 2

8) In reverse blocking state of SCR, anode is biased ______ with respect to cathode.

a) Negative

b) Positive

c) Positive or Negative

d) Zero

ANSWER: | 5-a | 6-c | 7-b | 8-a |

9) In forward blocking state of SCR, anode is biased ______ with respect to the cathode.

a) Negative

b) Positive

c) Positive or Negative

d) Zero

10) In reverse blocking state of SCR, _____ junction in reverse biased and ______ junction in forward biased.

a) J1, J2 and J3

b) J3, J1 and J2

c) J1 and J3, J2

d) J1 and J2, J3

11) In forward blocking state of SCR, _____ junction in reverse biased and ______ junction in forward biased.

a) J2, J1 and J3

b) J3, J1 and J2

c) J1 and J3, J2

d) J1 and J2, J3

12) Turn off time of the SCR is ______.

a) 1us to 10us

b) 100us to 10ms

c) 50us to 500us

d) 5us to 50us

ANSWER: | 9-b | 10-c | 11-a | 12-d |

Power Electronics MCQ #15

Power System MCQ #20

2019-07-26T00:39:00.000-07:00

Power System MCQ 265 to 268:

265) In electrical power system network, which part operates in the highest voltage level?

(a) Generating station

(b) Transmission system

(c) Distribution system

(d) Load

266) The reliability of power system is _____ in mesh type network compared to the nodal type network.

(a) high

(b) low

(c) same as

(d) high or low

267) The mesh type network is also known as _____ type network.

(a) Radial

(b) Longitudinal

(c) Loop

(d) None of the above

268) In underground distribution system, low tension cables used in ______ voltage level.

(a) below 1000 V

(b) up to 11 kV

(c) between 22 kV to 33 kV

(d) more than 33 kV

ANSWER: | 265-b | 266-a | 267-c | 268-a |

Power System MCQ 268 to 272:

269) For insulation in underground cable, the dielectric constant of PVC is ____.

(a) 3.5

(b) 2

(c) 10

(d) 5

270) A _______ is a bus where active power (P) and reactive power (Q) are known.

(a) generator bus

(b) load bus

(c) slack bus

(d) none of the above

271) A _______ is a bus where magnitude of bus voltage (V) and the corresponding generated power (P) are known.

(a) generator bus

(b) load bus

(c) slack bus

(d) none of the above

272) A _______ is a bus where magnitude of bus voltage (V) and phase angle of bus voltage are specified.

(a) generator bus

(b) load bus

(c) slack bus

(d) none of the above

ANSWER: | 269-d | 270-b | 271-a | 272-c |

Power System MCQ 273 to 276:

273) ______ is used when a generating unit is to be taken out for maintenance or repair.

(a) Hot reserve

(b) Cold reserve

(c) Spinning reserve

(d) Operating reserve

274) _____ is provided to meet the load demand under forced outage condition.

(a) Hot reserve

(b) Cold reserve

(c) Spinning reserve

(d) none of the above

275) ______ is provided to meet minute to minute load variations and any extra load due to load forecasting errors.

(a) Hot reserve

(b) Cold reserve

(c) Spinning reserve

(d) none of the above

276) A ______ is a failure in a power system of interconnected parts in which the failure of a part can triggers the failure of successive parts.

(a) Brown out

(b) Black out

(c) Cascade tripping

(d) B and C both

ANSWER: | 273-b | 274-a | 275-c | 276-d |

Power System MCQ #19

Power System MCQ #19

2019-07-25T00:47:00.000-07:00

Power System MCQ 253 to 256:

253) What are the advantages of gas turbine power plants?

(a) no standby loss and requiring small building space

(b) simple lubrication and high reliability

(c) simplicity in design and installation

(d) all of the above

254) Which of the following fuel is used in gas turbine power plants?

(a) kerosene, natural gas

(b) gas oil, diesel oil

(c) residual oil

(d) all of the above

255) The exhaust temperature of gas turbine is about _____

(a) 540°C

(b) 150°C

(c) 240°C

(d) 650°C

256) The fuel consumption of gas turbine power plant is about _____ output.

(a) 0.40 – 0.80 kg per kWh

(b) 0.2 – 0.25 kg per kWh

(c) 0.50 – 1.00 kg per kWh

(d) 1.0 – 2. Kg per kWh

ANSWER: | 253-d | 254-d | 255-a | 256-b |

Power System MCQ 257 to 260:

257) A gas turbine works on _____ cycle.

(a) Rankine

(b) dual

(c) Carnot

(d) Brayton

258) In which of the following the gas turbines are not widely used?

(a) as a base load

(b) as standby power plants

(c) as peak load

(d) in combination with steam power plant

259) Which of the following compressor is used in gas turbine power plants?

(a) reciprocating compressor

(b) multistage axial flow compressor

(c) either a or B

(d) screw compressor

260) In closed cycle gas turbine power plant, the work ratio is depending

(a) temperature ratio, pressure ratio and specific heat ratio

(b) specific heat ratio and pressure ratio

(c) specific heat ratio and temperature ratio

(d) only specific heat ratio

ANSWER: | 257-d | 258-a | 259-b | 260-a |

Power System MCQ 261 to 264:

261) Hydroelectric power stations are usually located in

(a) high hilly areas

(b) small hilly areas

(c) Plain areas

(d) any of the above

262) In hydropower station the amount of storage can be determined with the help of _____

(a) Flow duration curve

(b) Hydrograph

(c) Mass curve

(d) Storage

263) Why diesel power plant is suitable for peak load plants?

(a) because of quick starting and absence of standby losses

(b) because of high operating cost

(c) because of lower installation cost per kW as compared to steam power plants

(d) all of the above

264) The specific fuel consumption in diesel power plant at full load is about _____ kg per kWh.

(a) 0.23

(b) 1.23

(c) 2.3

(d) 3.5

ANSWER: | 261-a | 262-b | 263-a | 264-a |

Basic Electrical MCQ #19

2019-07-22T21:00:00.000-07:00

1) What is the phase difference between voltage and current, if AC circuit consist only resistance?

(a) 45º

(b) Zero

(c) 90º

(d) 270º

2) What is the phase difference between voltage and current, if AC circuit consist of purely inductive load?

(a) 45º

(b) Zero

(c) 90º

(d) 270º

3) What is the power factor of AC circuit with purely inductive load?

(a) leading

(b) lagging

(c) unity

(d) fluctuate between leading and lagging

4) Impedance of purely inductive circuit is expressed by______.

(a) Z = R + j XC

(b) Z = j XL

(c) Z = R

(d) Z = j XL + R

ANSWER: | 1-B | 2-C | 3-B | 4-B |

5) what is the phase difference between the voltage and current of ac circuit consist only capacitor?

(a) 45º

(b) Zero

(c) 90º

(d) 270º

6) In a purely capacitive circuit current ______ voltage by _______

(a) lags, 90

(b) leads, 90

(c) in phase

(d) out of phase

7) Which of the following represent ohm’s law for purely capacitive circuit?

(a) V = I Xc

(b) V = I Xl

(c) V = I

(d) Xc = I/V

8) In purely capacitive circuit, the resistive part is ______

(a) infinite

(b) finite

(c) unity

(d) zero

ANSWER: | 5-C | 6-B | 7-A | 8-D |

9) What is the unit of impedance (Z)?

(a) Weber per meter

(b) Henry per meter

(c) ohm per meter

(d) ohm

10) What is unit of susceptance?

(a) Siemens

(b) ohms

(c) Henry

(d) Farad

11) Find voltage across R and L if a series circuit of R= 20 ohms and L = 20 mH and supply is 60 V with 100 Hs.

(a) 31.9 V and 50.8 V

(b) 5.08 V and 3.19 V

(c) 50.8 V and 31.9 V

(d) 51.8 V and 32.9 V

12) which of the following is reciprocal of impedance?

(a) capacitance

(b) Admittance

(c) inductance

(d) reactance

ANSWER: | 9-D | 10-A | 11-C | 12-B |

Power System MCQ #18

2019-07-19T20:09:00.000-07:00

Power System MCQ 241 to 244:

241) In thermal power plant, the super-heater is a device

(a) increases the steam temperature above the saturation temperature

(b) which removers the last traces of moisture from the saturated steam leaving the boiler

(c) which removers the last traces of moisture from the saturated steam leaving the turbine exhaust

(d) Both A and B

242) From below options, which is a type of super heater

(a) radiant superheaters

(b) combinations of radiant and convection superheaters

(c) convection superheaters

(d) all of the above

243) The boiler efficiency is increased _____ by using economizer.

(a) 10-12%

(b) 5%

(c) 15-20%

(d) 5-10%

244) In modern economizer, the temperature of the feed water is raises from about ___ °C to ___ °C

(a) 100, 150

(b) 247, 276

(c) 300, 350

(d) 80, 120

ANSWER: | 241-D | 242-D | 243-A | 244-B |

Power System MCQ 245 to 248:

245) The design of boiler depends upon the ______ of the boiler.

(a) characteristic of operating labor, life and efficiency

(b) height, weight, bulk

(c) portability, safety

(d) all of the above

246) The selection and size of the boiler is depending upon which factor/s?

(a) portable load factor

(b) operating temperature and pressure

(c) the output required in term of amount of steam per hour

(d) all of the above

247) Which material is used in the boiler furnace wall _____.

(a) cement material

(b) refractory material

(c) Asbestos material

(d) cement with concrete material

248) In boiler the combustion of coal is controlled by

(a) the damper opening

(b) quantity of coal entering the grate

(c) controlling the grate speed

(d) all of the above

ANSWER: | 245-D | 246-D | 247-B | 248-D |

Power System MCQ 249 to 252:

249) In combustion of coal, air drawn from atmosphere to combustion chamber is through

(a) forced draught fan

(b) induced draught fan

(c) Both A and B

(d) naturally

250) The function of deaerator is to

(a) increase the dissolved gases

(b) reduced conductivity of water

(c) reduce the dissolved gases

(d) increase the pH value of water

251) The cooling water is passing through screens to _____

(a) remove the matters

(b) eliminate the choke the condensate tube

(c) increase the conductivity of water

(d) Both A and B

252) In evaporator, the water is heated by ____

(a) high pressure heater

(b) economizer

(c) low pressure heater

(d) turbine exhaust steam

ANSWER: | 249-C | 250-C | 251-D | 252-C |

Power System MCQ #18

Power Electronics MCQ #15

2019-04-28T23:16:00.000-07:00

1) BJT has _____ operating region.
  a) 1
  b) 2
  c) 3
  d) 4

2) The BJT is supposed to work as an amplifier, the circuit is so designed to bias it in _______ of operation.
  a) Active region
  b) Cut-off region
  c) Saturation region
  d) None of the above

3) BJT will work in cutoff region when it is ______ and in saturation region when it is ______.
  a) OFF, OFF
  b) ON, OFF
  c) OFF, ON
  d) ON, ON

4) When the switch is _______, it has zero voltage drop across it and carries full current through it, and when it is in _______ condition.
  a) ON, OFF
  b) ON, ON
  c) OFF, OFF
  d) OFF, ON

ANSWER: | 1-c | 2-a | 3-c | 4-a |

5) When positive terminal of a voltage source is connected to the n-type region and the negative terminal of the source is connected to the p-type region then the pn junction is said to be in_______ condition.
  a) Forward biased
  b) Reverse biased
  c) Both forward and reverse biased
  d) Cannot predict

6) When there is no voltage applied across the p n junction, the potential developed across the junction is _______ volts at 25 C for germanium pn junction.
  a) 0.5
  b) 0.7
  c) 0.8
  d) 0.3

7) When there is no voltage applied across the p n junction, the potential developed across the junction is _______ volts at 25 C for silicon pn junction.
  a) 0.5
  b) 0.7
  c) 0.8
  d) 0.3

8) Saturation current in PN junction is ____ A.

a) 10^-9 to 10^-18 A

b) 10^-19 to 10^-28 A

c) 10^-1 to 10^-8 A

d) 10^-1 to 10^-2 A

ANSWER- | 5-b | 6-d | 7-b | 8-a |

9) The forward biased p-n junction resistance is rd ohm it is called _______.

a) AC resistance

b) Dynamic resistance

c) DC resistance

d) (a) and (b) both

10) The depletion layer ______ the transition capacitance of PN junction value goes down.

a) decrease

b) increase

c) both

11) ________ is the time taken by the electrons to move from n-type region to p-type region and p-type region to n-type region.

a) Storage Time

b) Transition Time

c) Reverse Recovery Time

d) Fall time

12) ________ is sum of the storage time and transition time.

a) Storage Time

b) Transition Time

c) Reverse Recovery Time

d) Fall time

ANSWER: | 9-d | 10-a | 11-a | 12-c |

Basic Electrical MCQ #18

2019-04-15T21:01:00.000-07:00

1) The rate of change of charge with respect to time is called as ______.

(a) Power

(b) Current

(d) Flux density

2) The direction of flow of conventional current is always ______.

(a) Same as compared to that of the electron current

(b) Undefined

(d) Both A and B

3) The force between like charge _____ and unlike charge ______.

(a) Repulsive, Attractive

(b) Attractive, Attractive

(d) Attractive, Repulsive

4) The conventional current always flow from ______ potential?

(a) Negative to Positive

(b) Positive to Negative

(d) Positive to Positive

ANSWER: | 1- b | 2-c | 3-a | 4-b |

5) The electron and proton contain _______and _______ charge?

(a) Negative, Positive

(b) Positive, Positive

(d) Positive, Negative

6) The property of material to oppose the flow of current is called _____

(a) Conductance

(b) Inductance

(d) Resistance

7) If the length of the conducting material is increases, then _____

(a) Resistance of the material increases

(b) Resistance of the material remains same

(d) None of the above

8) The unit of resistivity is _____.

(a) Ohm-ohm

(b) Ohm-meter

(d) Ohm per meter

ANSWER: | 5-a | 6-d | 7-a | 8-b |

9) A material is classified on the basis of electrical property.

(a) Conductors

(b) Insulators

(d) All of the above

10) The length of conductor is doubled and its area remains same then its resistance will be _____

(a) Remains same

(b) Increased by 4 time

(d) None of the above

11) The current density is the ratio of____?

(a) Current per unit area

(b) Current per unit resistance

(d) All of the above

12) A 1 ampere is equal to ______emu of current?

(a) 1/40 emu of current

(b) 1/20 emu of current

(d) 1/10 emu of current

ANSWER: | 9-d | 10-c | 11-a | 12-d |

Electrical Machine MCQ #17

2019-04-06T00:40:00.002-07:00

For more article and MCQ click here;

Electrical Article

1) Which of the following material is used for magnetic core of the transformer?

(a) silicon steel

(b) iron

(c) cast steel

(d) cast iron

2) The magnetic core and yokes of the transformer is made up of laminated ______

(a) cast steel

(b) electrotechnics steel

(c) cast iron

(d) hard drawn copper

3) The transformer grade steel consisting of _______

(a) 3.5% of silicon

(b) 3.5% copper

(c) 3.5% of iron

(d) all of the above

4) The silicon content in transformer core also affect the

(a) mechanical properties

(b) electrical properties

(c) chemical properties

(d) all of the above

ANSWER: | 1-a | 2-b | 3-a | 4-a |

5) The steel used for transformer core may be

(a) cast steel

(b) hot rolled

(c) cold rolled

(d) B or C

6) Generator transformers are ____________

(a) Step-up transformers

(b) Step-down transformers

(c) Auto-transformers

(d) One-one transformers

7) Station transformers are generally used for __________

(a) Providing generator voltage to transmission

(b) Providing power to load from transmission

(c) Isolating DC

(d) To supply power section auxiliary

8) On-load power factor for generator transformer is __________

(a) high

(b) low

(c) can’t define

(d) zero

ANSWER: | 5-d | 6-a | 7-d | 8-a |

9) A star connected three phase transformers is provided with tertiary delta connected winding which allows the flow of

(a) Second harmonic of exciting current

(b) Third harmonic of exciting current

(c) Fifth harmonic of exciting current

(d) Seventh harmonic of exciting current

10) In a step-down autotransformer, if the transformation ratio increases then the saving of copper

(a) Increases

(b) Decreases

(c) Remains same

(d) None of these

11) Overheating of transformer windings and of load are due to ________

(a) third harmonic currents

(b) third harmonic voltages

(c) fifth harmonic currents

(d) fifth harmonic voltages

12) In 4-wire star connection 3rd harmonic currents may flow through __________

(a) lines

(b) phases

(c) from fourth wire to neutral

(d) all connections

ANSWER: | 9-b | 10-a | 11-a | 12-d |

Electrical Machine MCQ #16

2019-04-05T00:57:00.002-07:00

1) The concentric type winding of transformer can be classified as
A) continuous disc winding
B) helical and crossover winding
C) cylindrical winding
D) all of the above

2) The winding of the transformer should be mechanically stable in respect of
A) the force appearing when sudden short circuits of transformer occurs
B) the force appearing load through off of transformer occurs
C) load consumes too much reactive power
D) none of the above

3) The transformer windings are made up of ______
A) aluminum strip
B) solid copper
C) stranded copper
D) all of the above

4) In transformer winding to reduce eddy current losses in the conductors______
A) several series straps are preferred
B) several parallel straps are preferred
C) one large strap is preferred
D) Both A or B

ANSWER: | 1-D | 2-A | 3-D | 4-D |

5) A sandwich type winding is employed for
A) shell type transformer
B) core type transformer
C) step down transformer
D) step up transformer

6) In core type transformer _____ winding is employed.
A) sandwich type winding
B) concentric type winding
C) rectangular type winding
D) all of the above

7) Which one of the following has the better magnetic properties in the direction of rolling?
A) cold rolled steel
B) hot rolled steel
C) cast iron
D) aluminium

8) The thickness of lamination of transformer core varies from _____
A) 0.35 mm to 0.5 mm
B) 0.25 mm to 0.35 mm
C) 0.45 mm to 0.55 mm
D) 0.55 mm to 0.65 mm

ANSWER: | 5-A | 6-B | 7-A | 8-A |

9) The thickness of lamination should not be below 0.3 mm because
A) the lamination becomes mechanically strong and tends to buckle
B) the lamination becomes mechanically weak and tends to buckle
C) the lamination becomes electrically strong and tends to buckle
D) the lamination becomes electrically weak and tends to buckle

10) In high capacity transformer, varnish insulation is used instead of paper insulation because of paper insulation
A) occupies too large percentage of the stack cross section
B) its heat resisting and heat conducting properties are worse
C) its mechanical strength is worse
D) all of the above

11) What are the most important requirements of winding of the transformer?
A) efficiency of transformer in services
B) economical in initial cost with view of market availability of copper
C) heating conditions of winding should meet standard requirements
D) all of the above

12) A part of the magnetic circuit which carry the transformer winding are called_____
A) yoke
B) limbs
C) legs
D) Both B and C

ANSWER: | 9-B | 10-D | 11-D | 12-D |

Power Electronics MCQ #14

2019-03-27T22:11:00.001-07:00

1) DIAC is _____ terminal device.

(a) 1

(b) 2

(c) 3

(d) 4

2) Which of the following is bi-directional device?

(a) SCR

(b) Diode

(c) DIAC

(d) All of the above

3) Which of the following is unidirectional device?

(a) SCR

(b) TRIAC

(c) DIAC

(d) None of the above

4) SCR can be turned on by ______

(a) Raising temperature

(b) Focusing light

(c) Applying high voltage

(d) All of the above

ANSWER: | 1-b | 2-c | 3-a | 4-d |

5) In construction of power transistor, the emitter layer is ______, the base layer is _______ and the drift region is ______.

(a) Heavily doped - Lightly doped - Moderately doped

(b) Heavily doped - Moderately doped - Lightly doped

(c) Lightly doped - Moderately doped - Heavily doped

(d) Moderately doped - Heavily doped - Lightly doped

6) In active region of operation of power transistor, the transistor works as _______

(a) Amplifier

(b) Open circuit

(c) Short circuit

(d) (b) and (c) both

7) In construction of power MOSFET, ____ layer is used to separate GATE terminal and P layer.

(a) SiO₂

(b) N+ layer

(c) N- layer

(d) P+ layer

8) What is the full-form of SITH? (SITH is a power electronic switch)

(a) Static induction thyristor

(b) Silicon induction transistor

(c) Static induction transistor

(d) State induction thyristor

ANSWER: | 5-b | 6-a | 7-a | 8-a |

9) _____ is used to trigger the TRIAC.

(a) SCR

(b) UJT

(c) DIAC

(d) Both (b) and (c)

10) “On state voltage drop across IGBT is less than the MOSFET.” This statement is TRUE or FALSE.

(a) TRUE

(b) FALSE

11) Once _____ is turned on, the gate will not have control on the operation.

(a) Diode

(b) IGBT

(c) MOSFET

(d) SCR

12)

This is a symbol of which device?

(a) SCR

(b) DIAC

(c) TRIAC

(d) BJT

ANSWER: | 9-d | 10-a | 11-d | 12-b |

Power system MCQ #17

2019-03-25T20:32:00.000-07:00

Power System MCQ 229 to 232:

229) Why demand of electrical energy is increasing day by day?

(a) Electrical energy is a convenient form of energy.

(b) It is easy control.

(C) Greater flexibility

(D) All of the above

230) What is/are the limitation of solar energy?

(a) It requires large area for generation of even a small amount of power

(b) It cannot be used in cloudy days or a night

(c) It is uneconomical method

(d) All of the above

231) How many tons of coal will produce the energy is equal to energy produced by 1 kg uranium?

(a) 3000 tones

(b) 4000 tones

(c) 4500 tones

(d) 5000 tones

232) What is/are the unit of mechanical energy in M.K.S. system?

(a) Newton-meter

(b) Joule

(c) Both

(d) None of the above

ANSWER: | 229-d | 230-d | 231-c | 232-c |

Power System MCQ 233 to 236:

233) 1 kWh = ………………… watt-sec

(a) 36x 10^3

(b) 36x 10^4

(c) 36x 10^5

(d) 36x 10^9

234) 1 calorie = ……………. Joules

(a) 3.25

(b) 3.90

(c) 4.02

(d) 4.18

235) 1kWh = …………... kcal

(a) 780

(b) 860

(c) 950

(d) 1030

236) Which of the following cycle steam power station basically works on?

(a) Otto cycle

(b) Rankine cycle

(c) coal and ash cycle

(d) Cooling cycle

ANSWER: | 233-c | 234-d | 235-b | 236-b |

Power System MCQ 237 to 240:

237) Which of the following equipment of steam power plant is convert steam energy into mechanical energy?

(a) Boiler

(b) Economizer

(c) Generator

(d) Steam turbine

238) At where coal is pulverized in thermal power plant?

(a) Boiler

(b) Coal storage plant

(c) Ash storage plant

(d) Superheater

239) Which of the equipment converts water into steam at high pressure and temperature in thermal power plant?

(a) Superheater

(b) Economizer

(c) Boiler

(d) Turbine

240) To arrange the sequence of flow of flue gases in power plant?

(a) Boiler – air preheater – economizer – superheater –chimney

(b) Boiler – economizer – superheater – air pre-heater – chimney

(c) Boiler – superheater – air pre-heater – economizer – chimney

(d) Boiler – superheater – economizer – air pre-heater – chimney

ANSWER: | 237-d | 238-b | 239-c | 240-d |

Basic Electrical MCQ #17

2019-03-22T22:13:00.000-07:00

1) If the frequency of the supply is increase, then reactance of inductive circuit is ______.
    (a) decrease
      (b) increase
      (c) remain same
      (d) inductive reactance does not depend on supply frequency

2) What is the value of reactance of a 2µF capacitor of 2.5 kHz?
      (a) 15.91 Ω
      (b) 159.1 Ω
      (c) 1591 Ω
      (d) 1.591 Ω

3) When the load connected to ac is purely resistive, the reactive part is ______.
      (a) equal to resistive part
      (b) infinite
      (c) not defined
      (d) zero

4) In a purely capacitive circuit current _____voltage by _____
      (a) lags, 90
      (b) in phase
      (c) leads, 90
      (d) out of phase

ANSWER: | 1-b | 2-c | 3-d | 4-c |

5) Capacitive reactance is measured in____.
      (a) Henry
      (b) Farad
      (c) Weber
      (d) Ohms

6) A pure capacitor has its leakage resistance equal to___.
(a) infinite value
      (b) finite value
      (c) capacitance
      (d) unity

7) Arrange following alloys in decreasing order of their resistivity.
(a) Constantan- German silver- Monel metal
      (b) German silver- Constantan- Monel metal
      (c) Constantan- Monel metal- German silver
      (d) German silver- Monel metal- Constantan

8) Which of the following has highest dielectric strength?
      (a) Marble
      (b) Polystyrene
      (c) cotton
      (d) Transformer oil

ANSWER: | 5-d | 6-a | 7-a | 8-b |

9) The capacitance per unit volume is maximum for
      (a) mica capacitor
      (b) ceramic capacitor
      (c) air capacitor
      (d) electrolytic capacitor

10) Which of the following is/are not used as earth continuity conductors?
      (a) gas pipe
      (b) structural steel
      (c) oil pipe
      (d) All of the above

11) ____ type of wiring is mostly safe from fire and mechanical injury.
      (a) casing capping
      (b) CTS /TRS
      (c) conduit
      (d) cleat

12) The minimum height of lamp fitting from the ground level should be____.
      (a) 5 m
      (b) 1.5 m
      (c) 10 m
      (d) 1 m

ANSWER: | 9-d | 10-d | 11-b | 12-b |

Power System MCQ #16

2019-03-06T11:08:00.000-08:00

Power system MCQ 217 to 220:

(217) The electrical power produce at ______.

(a) Load center

(b) Generating station

(c) Substation

(d) Switchyard

(218) Which of the following system is universally adopted for generation and transmission of the electrical power?

(a) 3-phase, 3-wires system

(b) 3-phase, 4-wires system

(c) 2-phase, 2-wires system

(d) 1-phase, 2-wires system

(219) Which of the following system is universally adopted for distribution of the electrical power?

(a) 3-phase, 3-wires system

(b) 3-phase, 4-wires system

(c) 2-phase, 2-wires system

(d) 1-phase, 2-wires system

(220) _______ voltage rating is acceptable in primary transmission system.

(a) 33 KV

(b) 66 KV

(c) 110 KV

(d) 132 KV

ANSWER: | 217-b | 218-a | 219-b | 220-d |

Power system MCQ 221 to 224:

(221) Which of the following voltage rating(s) is/are acceptable in secondary transmission system?

(a) 110 KV

(b) 66 KV

(c) 33 KV

(d) All of the above

(222) In which transmission system, the inductance and capacitance are not considered?

(a) AC transmission system

(b) DC transmission system

(c) AC and DC transmission system

(223) Which of the following is/are protective device(s) of transmission line?

(a) Lightning arrestor

(b) Circuit breaker

(c) Relay

(d) All of the above

(224) Which of the following parameter(s) is/are considering while designing of power transmission line?

(a) Economic choice of conductor size

(b) Economic choice of transmission voltage

(c) Both a and c

(d) None of the above

ANSWER: | 221-d | 222-b | 223-d | 224-c|

Power system MCQ 225 to 228:

(225) The economic size of conductor can be determined by ______?

(a) Faraday’s law

(b) Fleming’s law

(c) Ohm’s law

(d) Kelvin’s law

(226) Which of the material used as insulating material between conductors in overhead line?

(a) Mica

(b) Paper

(c) Air

(d) Rubber

(227) Which of the following property is not of conductive material?

(a) High electrical conductivity

(b) High tensile strength

(c) Low cost

(d) High specific gravity

(228) Which of the reason(s) underground transmission system is not widely used?

(a) Power generally transmitted over a long distance

(b) Power is transmitted on high voltage for economic reason

(c) Both a and c

(d) None of the above

ANSWER: | 225-d | 226-c | 227-d | 228-c |

Power system MCQ #15

Power system MCQ #14

Power system MCQ #13

Electrical Machine MCQ #15

2019-03-01T04:52:00.002-08:00

1) The purpose in breather in a transformer is to

a) provide insulation to the winding

b) provide cooling to the winding

c) extract moisture from the air

d) reduce the copper loss

2) What is the use of auto-transformer?

a) Isolating transformer

b) Variable transformer

c) Control transformer

d) Current transformer

3) The open circuit test is conduct in transformer to find?

a) Copper loss

b) Core loss

c) Efficiency

d) Insulation resistance

4) Which of the following loss is not present in the transformer?

a) Core loss

b) Copper loss

c) Friction loss

d) Eddy current loss

ANSWER: | 1-c | 2-b | 3-b | 4-c |

5) The no load test is conduct in transformer to find?

a) Copper loss

b) Core loss

c) Efficiency

d) Magnetizing current and loss

6) Which chemical is used in the breather of transformer?

a) Silica

b) Fiber

c) Plastic

d) Silica gel

7) Which winding of the transformer has more cross-sectional area?

a) High-voltage winding

b) low-voltage winding

c) Primary winding

d) Secondary winding

8) Short-circuit test on transformer is conducted to determine

a) Hysteresis loss

b) Core loss

c) Copper loss

d) Eddy current loss

ANSWER: | 5-d | 6-d | 7-b | 8-c |

9) In transformer, which winding has less cross-sectional area?

a) High-voltage winding

b) low-voltage winding

c) Primary winding

d) Secondary winding

10) Which test is conduct in transformer to determine temperature?

a) No-load test

b) Open circuit test

c) Sumpner’s test

d) Routine test

11) Harmonics in transformer result in

a) increase core loss

b) increase copper loss

c) magnetic interference with commutation circuit

d) all of the above

12) The noise resulting from vibration of lamination set by magnetic forces in transformer is termed as,

a) zoom

b) hum

c) boo

d) None of the above

ANSWER: | 9-a | 10-c | 11-d | 12-b |

Power System MCQ #15

2019-02-25T21:49:00.000-08:00

Power system MCQ 205 to 208:

205) Induction cup relay is operated due to changes in

(a) Current

(b) Voltage

(d) All of the above

206) Which relay is used for phase fault on short transmission line.

(a) Induction type

(b) Reactance

(d) None of the above

207) Negative sequence current is provided for which of the following protection?

(a) Generator

(b) Transmission line

(d) Motor

208) The single phasing relays are used for the protection of

(a) single phase motor only

(b) two phase motor only

(d) three phase motor

ANSWER: | 205-d | 206-b | 207-a | 208-d |

Power system MCQ 209 to 212:

209) Which of the following parameter can neglect for the representation of the short transmission line.

(a) Resistance

(b) Capacitance

(d) Reactance

210) The under-voltage relay is used for

(a) Generators

(b) Bus-bars

(d) All of the above

211) Which device receive voltage surge first in the transmission system?

(a) Relay

(b) Lightning arresters

(d) Step-down transformer

212) Admittance relay is ______ relay.

(a) Directional

(b) Non-directional

(d) None of the above

ANSWER: | 209-b | 210-d | 211-b | 212-a |

Power system MCQ 213 to 216:

213) The fuse blows off by

(a) Burning

(b) Arcing

(d) None of the above

214) The power loss is an important factor for design of

(a) Motor

(b) Generator

(d) Feeder

215) Fuse is not used beyond ___A

(a) 20

(b) 100

(d) 50

216) A switchgear device is used for which purpose?

(a) Interrupting an electrical circuit

(b) Switching an electrical equipment

(d) Switching, controlling and protecting an electrical circuit and equipment

ANSWER: | 213-c | 214-c | 215-b | 216-d |

Basic Electrical MCQ #16

2019-02-23T09:36:00.000-08:00

1) The value of earth resistance inversely proportional to the square of the _____
(a) Current
(b) Distance
(c) Volume
(d) none of the above

2) Out of below mentioned factors, which factor(s) responsible to increase the earth resistance?
(a) rust between joints
(b) reduced amount of moisture in soil
(c) loose connections
(d) all of the above

3) Fuse works on _____ the principal of electricity.
(a) Electromagnetic
(b) Electrochemical
(c) Chemical
(d) Electic heating

4) For semi enclosed or rewirable fuse, the fusing factor is _____.
(a) less than one
(b) greater than one
(c) 2
(d) unity

Answer: | 1-b | 2-d | 3-d | 4-c |

5) The resistivity of the materials depends on which factors?
(a) cold working, temperature
(b) mechanical stress, alloying
(c) age hardening
(d) All of the above

6) A supper conductor may be used for_______.
(a) Rise temperature
(b) Generate electricity
(c) Generate magnetic field
(d) Create pressure

7) Dielectric constant for vacuum is___.
(a) 100
(b) 1
(c) infinite
(d) zero

8) Thermocouple work on which of the following effects?
(a) Seeback effect
(b) Thomson effect
(c) Joule law
(d) any of the above

Answer: | 5-d | 6-c | 7-b | 8-a |

9) Bronze is an alloy of
(a) copper and tin
(b) copper, lead and tin
(c) copper, zinc and tin
(d) copper and zinc

10) _______is piezo-electric material.
(a) silica sand
(b) polysterene
(c) Quartz
(d) plastic

11) How to minimize the hysteresis loss?
(a) by reducing operating frequency
(b) by reducing volume of the materials
(c) by selecting a material which has narrow hysteresis loop
(d) All of the above

12) The generation of emf due to electromagnetic induction was first obtained by_______.
(a) Hopkinson
(b) Fleming
(c) Rutherford
(d) Michael Faraday

Answer: | 9-d | 10-c | 11-d | 12-d |

Basic electrical MCQ #15

2019-02-12T11:02:00.000-08:00

1) Mobility is the ratio of ______
(a) Acceleration to velocity
(b) Drift velocity to applied electric field
(c) Applied electric field to Drift velocity
(b) Velocity to acceleration

2) The current is ______ proportional to____, according to the ohm’s law?
(a) Inversely, power
(b) Directly, Resistance
(c) Inversely, potential difference
(d) Directly, Potential difference

3) Ohm’s law is not applicable for____.
(a) Semiconductor devices such as diode, transistor, thyristors, SCR
(b) Magnetic coupled circuit like transformer
(c) Vacuum tube such as vacuum diode, triode, tetrode, pentode
(d) All of the above

4) The ohm's law is ______, if the temperature is not constant.
(a) Not applicable
(b) Applicable
(c) Applicable in any condition
(d) None of the above

ANSWER: | 1-b | 2-d | 3-d | 4-a |

5) Mass of Neutron is equal to the mass of ___?
(a) Proton
(b) Electron
(c) Nucleus
(d) Atom

6) The resultant resistance for series combination of R1, R2, and R3 is ______.
(a) RT = R1 + R2/R3
(b) RT = R1 + R2 + R3
(c) 1/RT = 1/R1 + 1/R2 + 1/R3
(d) RT = 1/R1 + 1/R2 + 1/R3

7) The resultant resistance for parallel combination of R1, R2, and R3 is ______.
(a) 1/RT = 1/R1 + 1/R2 + 1/R3
(b) RT = R1 + R2/R3
(c) RT = R1 + R2 + R3
(d) RT = 1/R1 + 1/R2 + 1/R3

8) The total resistance of the series combination of resistors is always ______ the individual resistance.
(a) Less than
(b) Equal to
(c) Higher than
(d) Not defined

ANSWER: | 5-a | 6-b | 7-a | 8-c |

9) The cut - in voltage for silicon and germanium are
(a) 0.3 V, 0.3 V
(b) 0.3 V, 0.7 V
(c) 0.7 V, 0.7 V
(d) 0.7 V, 0.3 V

10) If four bulb B1, B2, B3, and B4 are connected in series. If one of the bulb get damaged, than__.
(a) Remaining bulbs are glows
(b) Remaining bulbs are not glows
(c) Remaining bulbs B2 B3 are glows but B4
(d) All of the above

11) Two bulbs marked 100W,250V and 200W,250V are connected in series to 250V supply. Power consumed in circuit is equal to
(a) 100Watt
(b) 300Watt
(c) 150 watt
(d) 67Watt
[Hint: P = V2/R]

12) _____ is not same as Watt.
(a) Ampere x volt
(b) (Ampere)2 x ohm
(c) Ampere/volt
(d) Joule/sec

ANSWER: | 9-d | 10-b | 11-d | 12-c |

Basic Electrical MCQ #14

2019-02-06T21:47:00.000-08:00

1) Inside a conductor/conducting material, the movement of electrons is known as ______

(a) Ions

(b) Atoms

(d) Electrons, atoms and ions

2) The rate of change of charge with respect to time is called as ______

(a) Power

(b) Current

(d) Flux density

3) The current flowing between them is ______, If the potential difference between the two points is zero.

(a) Infinite

(b) Zero

(d) None of the above

4) The charge on each electron is ______ Coulomb?

(a) 1.6x10-16

(b) 1.9x10-19

(d) 1.6x10-19

ANSWER: | 1-c | 2-b | 3-b | 4-d |

5) The SI unit of electromotive force is ______

(a) Volt

(b) Current

(d) Ampere

6) The atoms contain of followings ______

(a) Proton

(b) Electron

(d) All of the above

7) The property of material to oppose the flow of current is called _______

(a) Conductance

(b) Resistance

(d) Impedance

8) The resistance of material depends upon which of the following ______

(a) Length of the material

(b) Resistivity of the material

(d) All of the above.

ANSWER: | 5-a | 6-d | 7-b | 8-d |

9) The best conductor of electricity is ______

(a) Copper

(b) Silver

(d) Aluminum

10) The resistivity is also called as ______

(a) Specific conductance

(b) Resistance

(d) All of the above

11) The current density is the ratio of ______?

(a) Current per unit area

(b) Area per unit current

(d) All of the above

12) An electric current is a ______ quantity.

(a) Vector

(b) Scalar

(d) None of the above.

13) The mass of electron is ____ kg?

(a) 9.11x10^-19

(b) 9.11x10^-31

(d) 6.25x10¹⁸

ANSWER: | 9-b | 10-c | 11-a | 12-b | 13-b |

Basic electrical MCQ #13

2019-01-04T20:30:00.002-08:00

1) In a circuit, a 29-ohm resistor carries a current of 3 A. Find the voltage across the resistor.

a) 23 V

b) 87 V

c) 3 V

d) 54 V

2) A current of 16 A divide in two paths of 8 ohms and 12 ohms respectively. Find the current in individual path.

a) 6.4 A, 9.6 A

b) 4.6 A, 6.9 A

c) 8 A, 8 A

d) 12 A, 1 A

3) The rating of fuse wire is always in

a) kWh

b) Ampere

c) Volt

d) Watt

4) The hot resistance of the bulb’s filament is higher compared to its cold resistance. In this case, the temperature co-efficient of the filament is

a) negative

b) 1

c) zero

d) positive

ANSWER: | 1-b | 2-a | 3-b | 4-d |

5) The insulation thickness depends on

a) the magnitude of voltage on the conductor

b) the magnitude of current following through it

c) both a) and b)

d) none of the above

6) An electric filament bulb can work on which power source?

a) DC source

b) AC source

c) Battery

d) all of above

7) Find the resistance of 220 V, 100 W lamp.

a) 484 ohms

b) 4.84 ohms

c) 48.4 ohms

d) 4840 ohms

8) Which method is used for absolute measurement of resistance?

a) Ohm’s law

b) Raleigh method

c) Wheatstone bridge

d) Lorentz method

ANSWER: | 5-a | 6-d | 7-a | 8-c |

9) The ratio of mass of proton to that of electron is nearby

a) 1840

b) 184

c) 18.4

d) 1.8

10) Three resistors are connected in parallel. Each resistor dissipates 20 W power. Find how much power is supplied by the voltage source.

a) 20 W

b) 60 W

c) 6.33 W

d) 40 W

11) It becomes more difficult to remove

a) first electrons from the orbit

b) second electrons from the orbit

c) third electrons from the orbit

d) cannot predict the answer

12) International ohm is defined as the resistance of

a) a cube of carbon

b) a cube of iron

c) the unit length of copper wire

d) a column of mercury

ANSWER: | 9-a | 10-b | 11-c | 12-d |

Basic electrical MCQ #12

2019-01-03T20:42:00.000-08:00

1) Three resistors are connected in delta connection. The resistance of each resistor is 15 ohms. Find the value of equivalent star resistance.

a) 10 ohms

b) 5 ohms

c) 7.5 ohms

d) 15 ohms

2) To move electrons in a particular direction, the electrical force or pressure is created is called as _______.

a) Electromotive force

b) Magnetomotive force

c) Electromechanical force

d) Mechanical force

3) By using _______, measuring range of ammeter can be extended.

a) high value of series resistance

b) low value of series resistance

c) low value of shunt resistance

d) high value of shunt resistance

4) In fan, which type of capacitor is used?

a) Mica

b) Electrolytic

c) Ceramic

d) none of the above

ANSWER: | 1-b | 2-a | 3-c | 4-c |

5) The relative permittivity is 5. Find its absolute permittivity.

a) 5/ϵ₀

b) 5ϵ₀

c) ϵ₀/5

d) ϵ₀

6) The unit of absolute permittivity of a medium is

a) n-m

b) farad/m

c) farad/coulomb

d) joule/coulomb

7) The magnetic lines of force are known as

a) the lines of magnetic flux

b) the lines of electromagnetism

c) the lines of magnetic field

d) none of the above

8) The unit of magnetic flux is

a) Wb/m

b) Wb

c) Wb/m³

d) Wb/m²

ANSWER: | 5-a | 6-b | 7-a | 8-d |

9) The unit of magnetomotive force is

a) weber

b) AT

c) tesla

d) ampere

10) The unit of permeance is

a) AT

b) AT/Wb

c) Henry

d) Wb/AT

11) The unit of reluctance is

a) AT

b) AT/Wb

c) Henry

d) Wb/AT

12) For current carrying conductor, the direction of force lying in magnetic field is given by,

a) Fleming left hand rule

b) Fleming right hand rule

c) Thumb rule

d) cork screw rule

ANSWER: | 9-b | 10-d | 11-b | 12-a |

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Electrical machine MCQ #14

2018-12-30T21:24:00.000-08:00

1) Two winding of transformers are connected by means of

(a) physically link

(b) inductively link

(c) conductively link

(d) not linked

2) Why tap changer is used in transformer?

(a) adjusting the primary and secondary voltage

(b) adjusting the secondary voltage

(c) adjusting the primary voltage

(d) none of the above

3) The power is transferred in auto transformer through ______.

(a) conduction process only

(b) induction process only

(c) mutual coupling

(d) both conduction and induction process

4) The rated secondary voltage of 220V for a transformer means the terminal voltage of 220V at which condition?

(a) rated full load

(b) no-load

(c) half full-load

(d) 1/3^rd of full load

ANSWER: | 1-b | 2-b | 3-d | 4-a |

5) The effect of armature reaction on the main flux is

(a) distorting

(b) demagnetizing

(c) distorting and demagnetizing both

(d) assisting

6) The synchronous reactance is the reaction due to

(a) armature reaction of the machine

(b) leakage flux

(c) either due to armature reaction or leakage flux

(d) combined reaction due to armature reaction and leakage flux

7) The short circuit characteristic of an alternator is

(a) always nonlinear

(b) always linear

(c) either of (a) or (b)

(d) none of the above

8) The power factor on which an alternator operates depends on the

(a) nature of the load being supplied

(b) speed of prime mover

(c) armature loss

(d) copper loss

ANSWER: | 5-c | 6-d | 7-b | 8-a |

9) A leading power factor load on an alternator implies that its voltage regulation shall be

(a) positive

(b) negative

(c) zero

(d) any one of the above

10) The power factor of an alternator is _______, under short circuit condition

(a) unity

(b) almost zero leading

(c) almost zero lagging

(d) none of the above

11) The magnitude of field flux ______ in a three-phase synchronous motor.

(a) varies with load

(b) remains constant at all loads

(c) varies with speed

(d) varies with power factor

12) The electromagnetic power varies _____, in a synchronous motor.

(a) inversely of applied voltage

(b) directly as square of applied voltage

(c) directly as applied voltage

(d) none of the above

ANSWER: | 9-d | 10-c | 11-b | 12-a |

Electrical machine #13

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Electrical machine MCQ PDF #14

Power electronics MCQ #13

2018-12-29T07:47:00.000-08:00

1) The resistance of a diode is equal to
a) Ohmic resistance of the P- and N- semiconductors
b) Junction resistance
c) Reverse resistance
d) Algebraic sum of (a) and (b) above

2) When forward biased, a diode
a) Blocks current
b) conducts current
c) Has a high resistance
d) drops a large voltage.

3) At room temperature of 25 °C, the barrier potential for silicon is 0.7 V.
lts value at 125° C is
a) 0.5V
b) 0.3V
c) 0.9V
d) 0.7V

4) An electron has
a) positive charge
b) Negative Charge
c) Neutral
d) none

Answer: | 1-d | 2-b | 3-a | 4-b |

5) Zener breakdown occurs
a) Due to normally generated minority carriers
b) In lightly doped junctions
c) Due to rupture of covalent bonds
d) Mostly in germanium junctions.

6) Which of the following is not a semiconductor
a) Gallium Arsenide
b) Indium
c) Germanium
d) Silicon

7) The depletion region in a PN Junction diode is due to
a) Reverse biasing
b) Forward biasing
c) Area Created by Crystal doping
d) an area void of current carriers

8) Forward bias resistance of ideal diode is
a) 10 ohms
b) 1M ohms
c) Infinity
d) zero

Answer: | 5-c | 6-b | 7-d | 8-d |

9) Emission coefficient of silicon (η) is
a) 0
b) 1
c) 2
d) None

10) The static resistance of a Diode is
a) its opposes the D.C current flow
b) its opposes the A.C current flow
c) resistance of the diode when forward bias
d) none

11) A breakdown which is caused by cumulative multiplication of carriers
through filed induced impact ionization occurs in
a) Zener diode
b) Tunnel diode
c) Varactor diode
d) avalanche diode

12) The capacitance appearing across a reverse biased semiconductor junction
a) increases with increase in bias voltage
b) decreases with increase in bias voltage
c) is independent of bias voltage
d) none of these

Answer: | 9-c | 10-a | 11-d | 11-b |

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