Explore topic-wise MCQs in Electromagnetic Theory.

This section includes 248 Mcqs, each offering curated multiple-choice questions to sharpen your Electromagnetic Theory knowledge and support exam preparation. Choose a topic below to get started.

1.

Consider two fields
E = 120 cos (106 t x) ay V/m
and H = A cos (106 t x) az A/m
The values of A and which will satisfy the Maxwell's equation in a linear isotropic homogeneous lossless medium with r = 8 and r = 2 will be
A (in A/m) (in rad/m)
A. 10.0105
B. 10.042
C. 20.0105
D. 20.042
A. A
B. B
C. C
D. D
Answer» E.
Discussion
2.

A plane wave is characterised by this wave is

^^
E = (0.5 x +xEj /2)ej t jk2
A. Linearly polarized
B. Circularly polarized
C. Elliptically polarized
D. Unpolarized
Answer» C. Elliptically polarized
Discussion
3.

The phase velocity for the TE10 mode in an air filled rectangular waveguide is

A. Less than C
B. Equal to C
C. Greater than C
D. None of these
Answer» D. None of these
Discussion
4.

A material has conductivity of 10 2 mho/m and a relative permittivity of 4 the frequency at which conduction current in the medium is equal to the displacement current is

A. 45 MHz
B. 90 MHz
C. 450 MHz
D. 900 MHz
Answer» B. 90 MHz
Discussion
5.

The dominant mode in a rectangular waveguide is TE10 because this mode has

A. No attenuation
B. No cut-off
C. No magnetic field component
D. The highest cut-off wavelength
Answer» E.
Discussion
6.

8-point charges of 1 nc each are located at the corners of a cube in free space that is 1 m on a side, then E at the centre is

A. 0 V/m
B. 5 V/m
C. 4 V/m
D. 5 V/m
Answer» B. 5 V/m
Discussion
7.

If a plane electromagnetic wave satisfies the equation
2Ex
 = e2
2Ex
z2 t2

the wave propagates in

A. x-direction
B. z-direction
C. y-direction
D. xy plane at an angle of 45 between x and z direction
Answer» C. y-direction
Discussion
8.

A stub having load impedance ZL and stub length / 2 then input impedance Zin is

A. Z
B.
C. Insufficient data
Answer» B.
Discussion
9.

A uniform plane wave travelling in air is incident on the plane boundary between air and another dielectric medium with r = 4. The reflection co-efficient for the normal incidence is

A. 0
B. 0.5 180
C. 0.333 0
D. 0.333 180
Answer» E.
Discussion
10.

A uniform place wave in air impinges at 45 angle on a lossless dielectric material with dielectric constant r. The transmitted wave propagate in a 30 direction with respect to the normal the wave of r is

A. 1.5
B.
C. 2
D.
Answer» D.
Discussion
11.

Three concentric conducting spherical surfaces of radii R1, R2 and R3 (R1 < R2 < R3) carry charges of 1, 2 and 4 coulombs respectively. The charges on the inner and outer surfaces of the outermost sphere will be respectively (in coulombs)

A. 0, 4
B. 3, 1
C. 3, 7
D. 2, 6
Answer» C. 3, 7
Discussion
12.

The maximum usable frequency of an ionospheric layer at 60 incidance and with 8 MHz. The critical frequency is

A. 16 MHz
B. 16/
C. MHz
D. 8 MHz
E. Approx. 6.93 MHz
Answer» B. 16/
Discussion
13.

Consider the following statements: For electromagnetic waves propagating in free space:
1. Electric field is perpendicular to direction of propagation.
2. Electric field is along the direction of propagation.
3. Magnetic field is perpendicular to direction of propagation.
4. Magnetic field is along the direction of propagation.
Which of these statements are correct?

A. 1 and 3
B. 1 and 4
C. 2 and 3
D. 2 and 4
Answer» B. 1 and 4
Discussion
14.

Unit of displacement density is

A. Coulomb/metre
B. Coulombs/(metre)
C.
D. Newton's law
E. Maxwell's equations
Answer» C.
Discussion
15.

A transmitting antenna radiates 251 watt isotropically. A receiving antenna locating 100 m away from the transmitting antenna has an effective aperture of 500 cm2. The total received power by the antenna is

A. 10 W
B. 20 W
C. 1 W
D. 100 W
Answer» E.
Discussion
16.

TEM wave has proper density 1.2 watt/m2 in a medium r = 3, r = 1. What is the value of E?

A. 22.85 V/m
B. 39.57 V/m
C. 13.19 V/m
D. None of these
Answer» B. 39.57 V/m
Discussion
17.

Consider the following statements regarding Maxwell's equations in differential form (symbols have their usual meaning)
1. For free space H = ( + j ) E
2. For free space . D =
3. For steady current H = j
4. For static electric field . D =
of these statements

A. 1 and 2 are correct
B. 2 and 3 are correct
C. 3 and 4 are correct
D. 1 and 4 are correct
Answer» D. 1 and 4 are correct
Discussion
18.

A plane wave propagating through a medium [Er = 8, Vr = 2 and = 0] has its electric field given by
^
E = 0.5
axe (z/3) sin (108 t 2) V/m
. The wave impedance in ohms is

A. 377
B. 198.5 180
C. 182.9 14
D. 133.3
Answer» B. 198.5 180
Discussion
19.

Medium 1 has the electrical permittivity 1 = 1.5 0 farad/m and occupies the region to the left of the x = 0 plane. Medium 2 has the electrical permittivity 2 = 2.5 0 and occupies the region to the right of x = 0 plane. If E1 in medium 1 is E1 = 2 ux 3 uy + uz V/m, find E2 in medium 2 is

A. (2 ux 7.5 uy + 2.5 uz) V/m
B. (2 ux 2 uy 0.6 uz) V/m
C. (1.2 ux 3 uy + 1 uz) V/m
D. (1.2 ux 2 uy + 0.6 uz) V/m
Answer» D. (1.2 ux 2 uy + 0.6 uz) V/m
Discussion
20.

The maximum usable frequency of an ionospheric layer at 60 incidence and with 8 MHz critical frequency is

A. 16 MHz
B. 16/
C. MHz
D. 8 MHz
E. about 6.93 MHz
Answer» C. MHz
Discussion
21.

E = uxx + uyy + uzz find the potential difference between (2, 0, 0) and (1, 2, 3) is given by

A. + 1 V
B. 1 V
C. + 5 V
D. + 6 V
Answer» D. + 6 V
Discussion
22.

A plane wave is characterized by

E = (0.5 x +yEj /2)ej t jkz

This wave is

A. Linearly polarized
B. Circularly polarized
C. Elliptically polarized
D. Unpolarized
Answer» D. Unpolarized
Discussion
23.

Consider the following statements regarding field boundary conditions:
1. The tangential component of electric field is continuous across the boundary between two dielectrics.
2. The tangential component of electric field at a dielectric-conductor boundary is non-zero.
3. The discontinuity in the normal component of the flux density at a dielectric-conductor boundary is equal to the surface charge density on the conductor.
4. The normal component of the flux-density is continuous across the charge-free boundary between two dielectrics.
Of these statements

A. 1, 2 and 3 are correct
B. 2, 3 and 4 are correct
C. 1, 2 and 4 are correct
D. 1, 3 and 4 are correct
Answer» E.
Discussion
24.

The polarization of wave with electric field vector E = E0 ej z t + z) (ax + ay) is

A. Linear
B. Elliptical
C. Left hand circular
D. Right hand circular
Answer» B. Elliptical
Discussion
25.

An open wire transmission line has R = 5 /m, L = 5.2 10 8 H/n, G = 6.2 10 3 S/m, C = 2.13 10 10 F/m. The signal frequency is 4 GHz. The impedance of the line for which there will be no reflection is in rectangular and polar form

A. 179.44 + j 26.50, 181.39 8.40
B. 15.623 + j 0.0205, 15.623 0.075
C. 200 + j 26.50, 181.39 8.40
D. 220 + j 26.50, 244 0.75
Answer» C. 200 + j 26.50, 181.39 8.40
Discussion
26.

Three concentric spherical shells of radii R1, R2, R3 (R1 < R2 < R3) carry charges 1, 2 and 4 coulombs, respectively. The charge in coulombs on the inner and outer surfaces respectively, of the outermost shell is

A. 0 and 4
B. 3 and 1
C. 3 and 7
D. 2 and 6
Answer» C. 3 and 7
Discussion
27.

The wavelength of a wave with propagation constant (0.1 + j 0.2 ) m 1 is

A. 2/
B. m
C. 10 m
D. 20 m
E. 30 m
Answer» C. 10 m
Discussion
28.

Consider the following statements associated with the basic electrostatic properties of ideal conductors:
1. The resultant field inside is zero.
2. The net charge density in the interior is zero.
3. Any net charge density in the interior is zero.
4. The surface is always an equipotential.
5. The field just outside is zero.
Of the statements:

A. 1, 2, 3 and 4 are correct
B. 3, 4 and 5 are correct
C. 1, 2 and 3 are correct
D. 2 and 3 are correct
Answer» B. 3, 4 and 5 are correct
Discussion
29.

For F1 layer maximum ionic density is 2.3 106 electrons per c.c. The critical frequency for this layer will be

A. 1.36 MHz
B. 13.6 MHz
C. 136 MHz
D. 1.36 10
E. MHz
Answer» C. 136 MHz
Discussion
30.

Match the following:
1. Wave tilt
2. Faraday rotation
(A) Under-water propagation
(B) Ground wave propagation
(C) Space wave propagation
(D) Ionospheric propagation

A. 1-A, 2-C
B. 1-B, 2-D
C. 1-A, 2-D
D. 1-B, 2-C
Answer» E.
Discussion
31.

A transmitting antenna radiates 251 W isotropically. A receiving antenna located 100 m away from the transmitting antenna has an effective aperture of 500 cm2. The total received power by the antenna is

A. 10 W
B. 1 W
C. 20 W
D. 100 W
Answer» E.
Discussion
32.

Choose the correct statements:
For a wave propagating in an air filled rectangular waveguide

A. Waveguide wavelength is never less than the free space wavelength.
B. Wave impedance is never less than the free space impedance.
C. Phase velocity is never less than the free space velocity.
D. TEM mode is possible if the dimensions of the waveguide are properly chosen.
Answer» D. TEM mode is possible if the dimensions of the waveguide are properly chosen.
Discussion
33.

The intrinsic impedance of a lossy dielectric medium is given by

A. j /
B. j /
C.
D.
E.
Answer» D.
Discussion
34.

160. Match the following:
(A) H = J
(B) Os E dl = d/dt s B ds
(C) J = / t
1. Continuity equation
2. Faraday's law
3. Ampere's law
4. Gauss's law
5. Biot-Savart law

A. A - 1, B - 2, C - 3
B. A - 4, B - 1, C - 5
C. A - 3, B - 5, C - 4
D. A - 2, B - 4, C - 1
Answer» E.
Discussion
35.

An air filled rectangular waveguide has dimensions 6 cm, 4 cm. The cut-off frequency for TE10 is

A. 2.5 GHz
B. 25 gHz
C. 25 MHz
D. 5 GHz
Answer» B. 25 gHz
Discussion
36.

A line of length n /4 (n is integer) in short circuited at the far end. The input impedance is

A. Zero
B. Infinite
C. Z
D.
E. None of these
Answer» C. Z
Discussion
37.

An open wire transmission line has primary constant
R = 20 /m G = 0.3 103 s/km
L = 0.25 1 m H/km C = 0.1 F/m
at a frequency of 1 kHz its characteristic impedance is

A. 169.73 , 25
B. 238.2 , 25
C. 715 , 25
D. 50 , 25
Answer» B. 238.2 , 25
Discussion
38.

For a quarter wave transformer characteristic impedance is related with input and load impedance

A. Z
B. =
C. Z
D. =
Answer» C. Z
Discussion
39.

A plane electromagnetic wave travelling along +z-direction, has its electric field given by Ex = 2 cos (t) and Ey = 2 cos (t + 90) the wave is

A. Linearly polarised
B. Right circularly polarised
C. Left circularly polarised
D. Elliptically polarised
Answer» D. Elliptically polarised
Discussion
40.

When N is the maximum electron density in per cubic metre. The critical frequency (fc) is given by

A. 9 N
B. 9N
C. 9
Answer» D.
Discussion
41.

The incoming solar radiation at a place on the surface of the earth is 1.2 kw/m2. The amplitude of the electric field corresponding to this incident power is nearly equal to

A. 80 m V/m
B. 2.5 V/m
C. 30 V/m
D. 950 V/m
Answer» E.
Discussion
42.

A material is described by following electrical parameters as a frequency of 10 GHz, = 106 mho/m = 0 and / 0 = 10. The material at this frequencies is considered to be
0 =
1
 10 9 F/m
36

A. A good conductor
B. A good dielectric
C. Neither a good conductor nor a good dielectric
D. A good magnetic material
Answer» B. A good dielectric
Discussion
43.

The characteristic impedance of a coaxial cable depends on:
1. Ratio of outer and inner diameter
2. Length of the cable
3. Logarithmic ratio of outer and inner diameter
4. Logarithmic ratio of outer and inner diameter and inversely as the square root of dielectric constant.
The correct statement is/are

A. 3 and 4
B. 2 and 3
C. 1, 3, 4
D. 4 only
Answer» E.
Discussion
44.

For incidence from dielectric medium ( 1) into dielectric medium 2 ( 2), the Brewster angle p and the corresponding angle of transmission t for 2/ 1 = 3 will be respecitively

A. 30 and 30
B. 30 and 60
C. 60 and 30
D. 60 and 60
Answer» D. 60 and 60
Discussion
45.

The ratio of the radii required to give a 60 ohm coaxial line filled with PTFE of r = 2, r = 1 is

A. 4.1: 1
B. 3.25: 1
C. 1: 1
D. 7.39: 1
Answer» B. 3.25: 1
Discussion
46.

A loop is rotating about the y-axis in a magnetic field

E = B0 cos ( t + )
axT
.The voltage in the loop is

A. Zero
B. Due to rotation only
C. Due to transformer action only
D. Due to both rotation and transformer action
Answer» E.
Discussion
47.

A transmission line of characteristic impedance Z0 = 50 ohms, phase velocity vP = 2 108 m/s, and length I = 1 m is terminated by a load ZL = (30 j 40) ohms. The input impedance of the line for a frequency of 100 MHz will be

A. (30 + j 40) ohms
B. (30 j 40) ohms
C. (50 + j 40) ohms
D. (50 j 40) ohms
Answer» C. (50 + j 40) ohms
Discussion
48.

Rectangular waveguide is designed to propagate the dominant mode TE10 at a frequency of 5 MHz. The cutoff frequency is 0.8 of signal frequency the raito of the waveguide height to width is 2 the dimension of the waveguide are

A. 3.75 cm, 1.875 cm
B. 4 cm, 2 cm
C. 8 cm, 4 cm
D. 2.54 cm, 1.27 cm
Answer» B. 4 cm, 2 cm
Discussion
49.

The shortest stub length in required to produce a reactance equal to Z0is

A.
B. 2
Answer» C.
Discussion
50.

Which of the following statement about the ratio E/H are true?
I. It is in the nature of an impedance
II. It is an impedance whose value is
III. It is a plane wave
IV. It is called intrinsic impedance of free space of value 120

A. I and II only
B. II and III only
C. I, II and IV only
D. II, III and IV only
Answer» D. II, III and IV only
Discussion