# Electromagnetic Field Theory MCQ Questions & Answers

Electromagnetic Field Theory MCQs : This section focuses on the "Electromagnetic Field Theory". These Multiple Choice Questions (MCQs) should be practiced to improve the Electromagnetic Field Theory skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode.

A. 4 cm
B. 1 cm
C. 2 cm
D. 8 cm

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Question 2

A rectangular waveguide measures 3 x 4.5 cm internally and has a 10 GHz signal propagated in it. Calculate the wave impedance for dominant mode.

A. 130 p
B. 1.3 p
C. 120 p
D. 12:00 PM

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Question 3

Calculate the directivity of an antenna for θE = 30°, θH = 60

A. 46
B. 23
C. 50
D. 100

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Question 4

The radiation resistance of a λ/16 wire dipole in free space will be nearly

A. 1 Ω
B. 3 Ω
C. 13 Ω
D. 30 Ω

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Question 5

For F1 layer the maximum ionic density is 2.3 x 104 electrons per cc. The critical frequency for this layer will be

A. 1.36 MHz
B. 13.6 MHz
C. 136 MHz
D. 1360 MHz

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Question 6

Find the noise factor for an antenna at 27°C with equivalent noise temperature 30°K

A. 20
B. 100
C. 300
D. 1.1

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Question 7

A rectangular metal waveguide filled with a dielectric of relative permittivity εr = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is

A. 2.5 GHz
B. 5 GHz
C. 10 GHz
D. 12.5 GHz

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Question 8

A parallel polarized wave is incident from air into paraffin having relative permittivity 3, the value of its Brewster angle is

A. 0°
B. 30°
C. 45°
D. 60°

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Question 9

Find the radiation resistance of an antenna of length λ/10 meter?

A. 8 Ω
B. 780 Ω
C. 7.8 Ω
D. 78 Ω

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Question 10

What is the characteristic impedance at 10 MHz?

A. 547.7 Ω
B. 54.7 Ω
C. 5.47 Ω
D. .547 Ω

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Question 11

ZL = 200 Ω and it is desired that Zi = 50 Ω The quarter wave transformer should have a characteristic impedance of

A. 100 Ω
B. 40 Ω
C. 10000 Ω
D. 4 Ω

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Question 12

A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls calculate the phase velocity for dominant mode.

A. 3 x 108 m/sec
B. 5 x 108 m/sec
C. 1.5 x 108 m/sec
D. 9 x 108 m/sec

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Question 13

A hollow rectangular waveguide has dimensions a = 2b. Calculate the amount of attenuation, if the frequency is 3 GHz, and b = 1 cm.

A. 49
B. 47.33
C. 50.33
D. 50

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Question 14

In a 100 turn coil, if the flux through each turn is (t3 - 2t)mWb, the magnitude of the induced emf in the coil at a time of 4 sec is

A. 46 mV
B. 56 mV
C. 4.6 V
D. 5.6 V

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Question 15

The electric field on the surface of a perfect conductor is 2V/m. The conductor is immersed in water with ε = 80 ε0. The surface charge density on the conductor is ((ε0 = 10-9/36p)F/m)

A. 0 c/m2
B. 2 c/m2
C. 1.8 x 10-11 c/m2
D. 1.14 x 10-9 c/m2

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Question 16

Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 1014 Hz in glass. Assume velocity of light is 3 x 108 m/sec in vacuum.

A. 4 μm
B. 3 μm
C. 2 μm
D. 1 μm

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Question 17

The divergence of the electric field intensity at any point equals

A. 1/4 pε0 times the volume charge density
B. l/ε0 times the volume charge density at that point
C. ε0 times the volume charge density at that point
D. the volume charge density at that point

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Question 18

Consider a loss less antenna with a directive gain of + 6 dB. If 1 mW of power is fed to it the total power radiated by the antenna will be

A. 4 mW
B. 1 mW
C. 7 mW
D. 1/4 mW

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Question 19

A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls Calculate group velocity for dominant mode.

A. 1.8 x 108 m/sec
B. 5 x 108 m/sec
C. 3 x 108 m/sec
D. 1.5 x 108 m/sec

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Question 20

The phase angle corresponding to λ/4 in a standing-wave pattern is

A. 30°
B. 90°
C. 135°
D. 180°

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Question 21

Which of the following should dominant wave have?

A. Lowest cut off frequency
B. Highest cut off frequency
C. No attenuation
D. No phase shift

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Question 22

The function f(x - vot) represent which of the following?

A. A stationary wave
B. A wave motion in forward direction
C. A wave motion in reverse direction
D. None of the above

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Question 23

A (75 - j 40) W load is connected to a co-axial line of z0 = 75ω at 6 MHz. The load matching on the line can be accomplished by connecting

A. a short circuit stub at the load
B. an inductance at the load
C. a short circuit stub at a specific distance from the load
D. a capacitance at a specific distance from the load

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Question 24

For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the value of propagation constant P will be

A. 15.9 radians/km
B. 31.8 radians/km
C. 63.6 radians/km
D. 105.4 radians/km

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Question 25

A uniform plane wave is one in which

A. x = 0
B. .
C. and are perpendicular
D. and lie in a plane

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Question 26

A transmission line is feeding 1 watt of power to a horn antenna having a gain of 10 dB. The antenna is matched to the transmission line. The total power radiated by the horn antenna into the free space is

A. 10 watts
B. 1 watt
C. 0.1 watt
D. 0.01 watt

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Question 27

A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be

A. 196 W
B. 73 W
C. 36.5 W
D. 18.25 W

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Question 28

The input impedance of short-circuited line of length l where λ/4 < l < λ/2, is

A. resistive
B. inductive
C. capacitive
D. none of the above

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Question 29

The velocity of electromagnetic wave in a good conductor is

A. 3 x 108 m/s
B. more than 3 x 108 m/s
C. very low
D. high

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Question 30

The Depth of penetration of EM wave in medium having conductivity σ at a frequency of 1 MHz is 25 cm. The depth of penetration at a frequency of 4 MHz will be

A. 6.25 cm
B. 12.50 cm
C. 50 cm
D. 100 cm

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Question 31

A plane electromagnetic wave travels in dielectric medium of relative permittivity 9. Relative to free space, the velocity of propagation in the dielectric is

A. increased by a factor of 9
B. increased by a factor of 3
C. unchanged
D. reduced by a factor of 1/3

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Question 32

A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing 10 cm. And if each array element feeding with 1 amp. current and operating at same frequency then find the half power beamwidth

A. 4°
B. 2°
C. 10°
D. 15°

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Question 33

Which one of the following potential does not satisfy Laplace's equations?

A. v = 10 xy
B. v = p cos φ

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