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 (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

Question 2

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

A. v = 10 xy

B. v = p cos φ

Question 3

What is the characteristic impedance at 10 MHz?

A. 547.7 Ω

B. 54.7 Ω

C. 5.47 Ω

D. .547 Ω

Question 4

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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

A. 46

B. 23

C. 50

D. 100

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

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

Question 15

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

Question 16

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°

Question 17

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

Question 18

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

A. 30°

B. 90°

C. 135°

D. 180°

Question 19

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

Question 20

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

Question 21

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

Question 22

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°

Question 23

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

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

Question 25

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

Question 26

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

Question 27

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

Question 28

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

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

Question 30

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

Question 31

A uniform plane wave is one in which

A. x = 0

B. .

C. and are perpendicular

D. and lie in a plane

Question 32

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

Question 33

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