# Electromagnetic Field Theory MCQs

## __________ acts as a depolarizer in a dry cell.

• A. ammonium chloride
• B. carbon powder
• C. manganese dioxide
• D. zinc chloride

• B. Silver
• C. Cobalt
• D. Iron

## ∇2 is

• A. vector
• B. scalar
• C. depend on direction
• D. none

• A. 8.6
• B. 6.8
• C. 8

## 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

• A. finite
• B. infinite
• C. unity
• D. zero

## A dipole antenna was radiating with some excitation in free space radiating a certain amount of the power. If this antenna is immersed in a lake where water is non-dissipative but has a dielectric constant of 81, the radiated power with the same excitation will

• A. decrease to finite non-zero value
• B. remain the same
• C. increase
• D. decrease to zero

## A dominant wave is characterised by which of the following?

• A. No attenuation
• B. Lowest cut off wavelength
• C. Highest cut off wavelength
• D. All of the above

## A higher directivity is specified by

• A. high gain low BW (Beamwidth)
• B. high gain high BW
• C. low gain high BW
• D. none of the above

• A. 57.73
• B. 33.33
• C. 0.11
• D. 11.11

## A medium is said to be isotropic when

• A. ∈ = 0
• B. ∈ = μ
• C. ∈ = σ
• D. ∈ is scalar constant

## A parabolic antenna produces a radiation pattern which is

• A. circularly polarized
• B. highly directional
• C. omnidirectional
• D. linearly polarized

• A. 942 m
• B. 2070 m
• C. 4978 m
• D. 5320 m

## A plane EM wave is travelling in an unbound loss less dielectric having μy = 1 and εy = 4, the time average Poynting vector of the wave is 5 W/m3 . The phase velocity vp (assuming velocity of light as 3 x 108 m/sec) is

• A. 1.5 x 108 m/sec
• B. 3 x 108 m/sec
• C. 2.5 x 108 m/sec
• D. 0.5 x 108 m/sec

• A. 31.11 mW
• B. 31.11 W
• C. 31.11 kW
• D. 31.11 MW

## A rectangular waveguide is a

• A. rectangular conducting wire to propagate electromagnetic waves
• B. hollow rectangular walled room carrying electromagnetic wave
• C. hollow rectangular conducting tube through which electromagnetic waves can be propagated
• D. tube antenna to transmit and receive electromagnetic waves

## A square corner reflector is used in

• C. point to point communication
• D. all of the above

## A square corner reflector is used in which of the following?

• B. Point-to-point communication
• D. All of the above

• A. 30°
• B. 60°
• C. 45°
• D. 90°

## A time varying magnetic field produces

• A. electric field only
• B. magnetic field only
• C. both magnetic and electric fields
• D. none of the above

## A transmission line has characteristics impedance of (75 + j 0.01) Ω and is terminated in a load impedance of (70 + j 50) Ω. The reflection coefficient will be

• A. 0.08 + j 0.32
• B. 0.32 + j 1.38
• C. 0.70 - j 2.97
• D. 1.1 + j 0.32

## A transmission line has primary constants R, L, G and C and secondary constant z0 and γ = (a + Jβ). If the line is loss less, then

• A. R = 0, G ≠ 0, and a = 0
• B. R = 0, G = , 0 and β = |r|
• C. G = 0, = β
• D. R = 0, G = 0, = 0, β = |r|

## A uniform wave have components

• A. in the perpendicular direction E existing while H is zero
• B. in the direction of propagation E existing while H is zero
• C. E and H are zero in direction perpendicular to direction of propagation
• D. E and H existing only in direction perpendicular to direction of propagation

• A. 0.13 W
• B. 0.88W
• C. 7.3 W
• D. 73 W

• A. MF
• B. VHF
• C. VLF
• D. HF

## A waveguide behave as

• A. high Pass filter
• B. low Pass filter
• C. band Pass filter
• D. all Pass filter

## A waveguide operated below cut off frequency can be used as

• A. phase shifter
• B. an attenuator
• C. an isolator
• D. none

## A Yagi antenna has a driven antenna

• A. only
• B. with a reflector
• C. with one or more directors
• D. with a reflector and one or more directors

## A λ/8 section of transmission line is determined of load impedance of (2 – j 5) Ω. If characteristic impedance of line is 10 Ω. Then input impedance of line is

• A. 10 Ω
• B. (6.9 + j 7.24) Ω
• C. (1.75 + j 3.098) Ω
• D. (2 - j 5) Ω

## Absolute permeability (μ) is given by __________ henry/metre

• A. 4 x 10-12
• B. 4 x 10-7
• C. 8.854 x 10-12
• D. 8.854 x 10-7

## After reflection from a plane conducting surface, the apparent velocity of electromagnetic wave becomes greater than the velocity of light in free space is called

• A. conventional velocity
• B. phase velocity
• C. propagation velocity
• D. group velocity

## Alternating current can induce voltage because it has magnetic field which is

• A. constant
• B. time varying
• C. stronger field than D.C.
• D. closed loop nature.

## An alternating current or voltage is that which

• A. changes in magnitude only
• B. changes in direction only
• C. both (a) and (b)
• D. has a random movement of electrons

## An antenna array pattern is to used for increasing

• A. gain
• B. directivity
• C. directive gain
• D. all

• A. 0.4456°
• B. 1.4456°
• C. 2.4456°
• D. 3.4456°

## An antenna having a high Q has

• A. lower BW
• B. higher BW
• C. flat response
• D. none of the above

## An electric charge Q is placed in a dielectric medium which of the following quantities are independent of the dielectric constant ε of the medium

• A. electric potential V and electric field intensity E
• B. displacement density D and displacement φ
• C. electric field intensity E and displacement φ
• D. electric potential V and displacement φ

## An electromagnetic wave incident on a perfect conductor is

• A. fully transmitted
• B. partially transmitted
• C. entirely reflected
• D. none of the above

## An electromagnetic wave incidents on a perfect insulator at an angle. If the wave is not entirely parallel polarized, then

• A. the reflected wave will be entirely polarized parallel to the plane of incidence
• B. there will be no reflection
• C. the reflected wave will be entirely polarized perpendicular to the plane of incidence
• D. any of the above