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

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

Question 3

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

A. 46

B. 23

C. 50

D. 100

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

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

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

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

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°

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

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

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

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

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

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

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

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

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

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

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

Question 20

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

A. 30°

B. 90°

C. 135°

D. 180°

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

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

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

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 uniform plane wave is one in which

A. x = 0

B. .

C. and are perpendicular

D. and lie in a plane

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

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

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

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

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 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

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°

Question 33

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

A. v = 10 xy

B. v = p cos φ