Important questions about Electromagnetic Field Theory. Electromagnetic Field Theory MCQ questions with answers. Electromagnetic Field Theory exam questions and answers for students and interviews.

3. Characteristic impedance of a transmission line is 50 ?. Input impedance of the open circuited line. Z oc = 100 + J150 ?. When transmission line is short circuited, then value of the input impedance will be

Options

A : 50 ?

B : 100 + J150 ?

C : 7.69 + J11.54?

D : 7.69 - J11.54 ?

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

Options

A : resistive

B : inductive

C : capacitive

D : none of the above

5. Z L = 200 ? and it is desired that Z i = 50 ? The quarter wave transformer should have a characteristic impedance of

Options

A : 100 ?

B : 40 ?

C : 10000 ?

D : 4 ?

6. For F 1 layer the maximum ionic density is 2.3 x 10 4 electrons per cc. The critical frequency for this layer will be

Options

A : 1.36 MHz

B : 13.6 MHz

C : 136 MHz

D : 1360 MHz

7. 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.

Options

A : 3 x 10 8 m/sec

B : 5 x 10 8 m/sec

C : 1.5 x 10 8 m/sec

D : 9 x 10 8 m/sec

8. A plane wave is characterized by the wave is

Options

A : linearly polarized

B : circularly polarized

C : elliptically polarized

D : unpolarized

10. What is the characteristic impedance at 10 MHz?

Options

A : 547.7 ?

B : 54.7 ?

C : 5.47 ?

D : .547 ?

1. The displacement flux density at a point on the surface of a perfect conductor is = 2( a x - 3 a z )c/m 2 pointing away from the surface. The charge density at that point c/m 2 will be

Options

A : 2

B : - 2

C : 4

D : - 4

2. The velocity of electromagnetic wave in a good conductor is

Options

A : 3 x 10 8 m/s

B : more than 3 x 10 8 m/s

C : very low

D : high

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

Options

A : 0°

B : 30°

C : 45°

D : 60°

5. 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

Options

A : 15.9 radians/km

B : 31.8 radians/km

C : 63.6 radians/km

D : 105.4 radians/km

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

Options

A : 6.25 cm

B : 12.50 cm

C : 50 cm

D : 100 cm

8. The divergence of the electric field intensity at any point equals

Options

A : 1/4 p ? 0 times the volume charge density

B : l/? 0 times the volume charge density at that point

C : ? 0 times the volume charge density at that point

D : the volume charge density at that point

9. 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

Options

A : 196 W

B : 73 W

C : 36.5 W

D : 18.25 W

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

Options

A : 2.5 GHz

B : 5 GHz

C : 10 GHz

D : 12.5 GHz

2. Calculate the directivity of an antenna for ? E = 30°, ? H = 60

Options

A : 46

B : 23

C : 50

D : 100

3. 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

Options

A : 4°

B : 2°

C : 10°

D : 15°

4. 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.

Options

A : 4 cm

B : 1 cm

C : 2 cm

D : 8 cm

5. A (75 - j 40) W load is connected to a co-axial line of z 0 = 75? at 6 MHz. The load matching on the line can be accomplished by connecting

Options

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

7. The electric field on the surface of a perfect conductor is 2V/m. The conductor is immersed in water with ? = 80 ? 0 . The surface charge density on the conductor is ((? 0 = 10 -9 /36 p )F/m)

Options

A : 0 c/m 2

B : 2 c/m 2

C : 1.8 x 10 -11 c/m 2

D : 1.14 x 10 -9 c/m 2

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