tag:blogger.com,1999:blog-46138584818733289532026-05-19T23:49:00.693+05:30Electromagnetic Theory - Electrostatics, Magneto-statics, Antennas, Transmission Systems.Uttam Agrawalhttp://www.blogger.com/profile/14782822449937945628noreply@blogger.comBlogger82125tag:blogger.com,1999:blog-4613858481873328953.post-24971676467611793362017-04-02T16:16:00.000+05:302017-04-02T16:47:32.269+05:30

1. Define A Uniform Plane Wave. Answer: In an uniform plane wave the electric and magnetic field vectors both lie in a plane and all such planes are parallel to each other. Also the amplitude and phase of vectors E and H are constant over the planes & they are always normal to the direction pf propagation. 2. State Gauss Divergence Theorem. Answer: This theorem states that the net flux

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01. State Three Ways In Which Forces Due To Magnetic Fields Can Be Experienced? Answer: There are at least three ways in which force due to magnetic fields can be experienced. The force can be due to a moving charged particle in a magnetic field. on a current element in an external magnetic field. between two current elements. 02. State The Lorentz Force Equation? Answer: The Lorentz

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01. How Can Materials Be Classified In Terms Of Their Electrical Properties? Answer:  Materials can be classified roughly as conductors (σ >> 1, εr = 1) and dielectrics (σ << 1, εr ≥ 1) in terms of their electrical properties σ and εr where σ is the conductivity and εr is the dielectric constant or relative permittivity. A material

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1. What Do You Mean By Dielectric Constant Of A Material ? Answer: Dielectric constant (k) or relative permittivity (εr) is defined as the ratio of capacitance of a capacitor with dielectric to the capacitance of same capacitor without dielectric. It generally describes the ability of a material to polarize and store a charge. Mathematically, k or εr = C/C0 . [Since C = q/V, we have εr = E0

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1. State Stokes Theorem. Answer: The line integral of a vector around a closed path is equal to the surface integral of the normal component of its curl over any surface bounded by the path ∫ H.dl = ∫ ∫ ( ∆ x H ) ds where, H is the Magnetic field intensity 2. State The Condition For The Vector F To Be Solenoidal. Answer: ∆ . F = 0 where, F = A i + B i + C i 3. State The Condition For

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The differences between Conduction Current and displacement current are: 1. Conduction current obeys ohm's law as V = (I / R) but displacement current does not obey ohm's law. 2. Conduction current density is represented by  whereas displacement current density is given by 3. Conduction current is the actual current whereas displacement current is the apparent current produced by

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1) An electric field strength of 10 µV/m is to be measured at an observation point θ = π/2, 500 km from a λ/4 monopole antenna operating in air at 50 MHz. (a) What is the length of the dipole? (b) Calculate the current that must be fed to the antenna. (c) Find the average power radiated by the antenna. (d) If a transmission line with Zo = 75 Ω is connected to the antenna, determine the

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INDEX Vector analysis is a mathematical tool with which electromagnetic (EM) concepts are most conveniently expressed. It's important to learn its rules and techniques first applying it. VECTOR ALGEBRA: - Scalars and Vectors. - Unit Vectors. - Position and Distance Vectors. - Vector Multiplication. - Components Of a Vector. - Numericals / Solved Examples. COORDINATE SYSTEMS &

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Q.4) A 70 Ω lossless line has s = 1.6 and θΓ = 300o. If the line is 0.6λ long, obtain (a) Γ, ZL, Zin (b) The distance of the first minimum voltage from the load Answer: a) Using the smith chart, locate S at s = 1.6. Draw a circle of radius OS. Locate P where θΓ = 300o . At P, | Γ | = OP / OQ = 2.1 cm / 9.2 cm = 0.228 Γ = 0.228 ∠300o Also at P, ZL = 1.15 – j0.48, ZL = Zo ZL =

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Q.1) A transmission line operating at 500 MHz has Zo = 80Ω, α = 0.04Np/m, β = 1.5 rad/m. Find the line parameters R, L, G and C. Answer: Since Zo is real & α ǂ 0, this is a distortionless line. Ro = α Zo = 0.04 x 80 = 3.2 Ω / m G = α / Zo = 0.04 / 80 = 5 x 10-4 Ω / m L = β Zo / ω = 1.5 x 80 / (2 π x 5 x 108 ) = 38.2 nH / m C = L G / R = 38.2 x 10-9 x 5 x 10-4 /

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19) At the far field, an antenna produces Calculate the directive gain and the directivity of the antenna? SOLUTION: 20) For a thin dipole λ/16 long, find the a) Directive gain b) Directivity c) Effective area d) Radiation resistance SOLUTION: a) On substituting we get, Gφ = 1.5 sin2θ b) Directivity, D = Gφ, max = 1.5 c)

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16) Sketch the normalized E-field and H-field patterns for a. A half-wave dipole b. A quarter-wave monopole. SOLUTION: a) b) The same as for λ/2 dipole except that the fields are zero for θ > π/2 as shown: 17) In free space, an antenna has a far zone field given by Determine the radiated power? SOLUTION: 18) At the far

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13) A 1-m-long car radio antenna operates in the AM frequency of 1.5 MHz. How much current is required to transmit 4 W of power? SOLUTION: This is a monopole antenna λ = c / f = (3 x 108) / (1.5 x 106) = 200 m In this case, it’s pretty clear that l << λ 14) An antenna located on the surface of a flat earth transmits an average power of 200 kW. Assuming that all the power is

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9) A Hertzian dipole at the origin in free space has dl = 20 cm and I = 10 cos2π107t A, find |Eθs| at the distant point (100, 0, 0). SOLUTION: λ = c / f = ( 3 x 108 ) / (107) = 30 m At (100, 0, 0), r = 100 m & θ = π / 2 10) A 2-A source operating at 300 MHz feeds a Hertzian dipole of length 5 mm situated at the origin. Find Es and Hs at (10, 30°, 90°). SOLUTION:  

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6) An antenna in air radiates a total power of 100 kW so that maximum radiated electric field strength of 12 mV/m is measured 20 km from the antenna.  Find its: (a) Directivity in dB (b) Maximum power gain if ηr = 98%. SOLUTION: a) G = 10 log 10 Gd = 10 log 10 (2.16) = 3.34 dB b) G = ηr Gd = 0.98 x 2.16 = 2.117 7) A C-band radar with an antenna 1.8 m in radius transmits 60

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3) A certain antenna with an efficiency of 95% has maximum radiation intensity of 0.5 W/sr. Calculate its directivity when (a) The input power is 0.4 W (b) The radiated power is 0.3 W SOLUTION: a) Prad = ηr Pin = (0.95) (0.4) = 0.38 4) Evaluate the directivity of an antenna with normalized radiation intensity SOLUTION: 5) Determine the maximum effective area of a

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1) An electric field strength of 10 µV/m is to be measured at an observation point θ = π/2, 500 km from a λ/4 monopole antenna operating in air at 50 MHz. (a) What is the length of the dipole? (b) Calculate the current that must be fed to the antenna. (c) Find the average power radiated by the antenna. (d) If a transmission line with Zo = 75 Ω is connected to the antenna, determine the

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Polarization is defined as the orientation of electric field as a function of direction. The polarization of the radio wave can be defined by direction in which the electric vector E is aligned during the passage of at least one full cycle. Also polarization can also be defined the physical orientation of the radiated electromagnetic waves in space. The polarization are of three types. They

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Consider a plane wave incident on a short dipole. The wave is assumed to be linearly polarized with electric field in the y direction. The current in the dipole is assumed constant and in the same phase over its entire length, and the terminating resistance is assumed equal to the dipole radiation resistance. The effective aperture of this dipole is given by Ae = 0.119 λ The directivity

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This page contains basic questions and short notes on some of the keywords on antenna theory: 96) What is Antenna matching? When the antenna is receiving with a load resistance matched to the antenna radiation resistance, maximum power is transferred to the load and the power is also re-radiated from the dipole. This is called antenna matching. 97) What is a Short Dipole? A short dipole

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This page contains basic questions and short notes on some of the keywords on antenna theory: Aperture represents the area of the antenna confining the effective radiations. The various types of antenna apertures are: Effective aperture. Scattering aperture. Loss aperture. Collecting aperture. Physical aperture. Effective aperture (Ae): It is the area over which the power is extrated from

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This page contains basic questions and short notes on some of the keywords on antenna theory: 91) Define Refractive index? It is defined as n = c / Vp where n = √εr 92)Define maximum Usable Frequency? The maximum Frequency that can be reflected back for a given distance of transmission is called the maximum usable frequency (MUF) for that distance. MUF = fcr sec φi 93) Define skip

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This page contains basic questions and short notes on some of the keywords on antenna theory: 86) What are the factors that affect the propagation of radio waves? Curvature of earth. Earth’ s magnetic field. Frequency of the signal. Plane earth reflection. 87) Define gyro frequency? Frequency whose period is equal to the period of an electron in its orbit under the influence of the earths

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This page contains basic questions and short notes on some of the keywords on antenna theory: 81) What is meant by diversity reception? To minimize the fading and to avoid the multi path interference the technique used are diversity reception. It is obtained by three ways: Space diversity reception. Frequency diversity reception. Polarization diversity. 82) Define Space diversity Reception

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This page contains basic questions and short notes on some of the keywords on antenna theory: 76) What is meant by Space Wave? It is made up of direct wave and ground reflected wave. Also includes the portion of energy received as a result of diffraction around the earth surface and the reflection from the upper atmosphere. 77) What is meant by Surface Wave? Wave that is guided along the

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