# Electromagnetics Transmission Lines and waveguides - Electronics Engineering

## Electromagnetics Transmission Lines and waveguides - Electronics Engineering

(1) In a dielectric medium of relative permittivity 9 a plane EM travels. The velocity of propagation in the dielectric relative to free space is

(A) Reduced by the factor of Y?
(B) Unchanged
(C) Increased by the factor of 3
(D) Decreased by the factor of 9

ANSWER: Reduced by the factor of Y?

(2) Polarization of EM wave is in

(A) The direction of magnetic field
(B) The direction of electric field
(C) The direction of electric and magnetic field
(D) None of the above

ANSWER: The direction of electric field

(3) Throughout the medium if ε, σ and μ are constant then it is known as

(A) Dielectric medium
(B) Distributed medium
(C) Homogeneous medium
(D) Perfect vacuum

(4) The wave, which is dominant, should have

(A) No attenuation
(B) No phase shift
(C) Lowest cut-off frequency
(D) Highest cut-off frequency

(5) The ratio of the tangential component of the electric field at the surface of conductor and the linear current density, which flows as a result of this electric field, is known as

(A) Reflection coefficient
(B) Refraction coefficient
(C) Trans-conductance
(D) Surface impedance

(6) Formation of a circular polarized wave results when

(A) Magnitudes of the two waves are same but phase difference is 90 °
(B) Magnitudes of the two waves are same
(C) Magnitudes of the two waves are same but phase difference is 0
(D) Phases of the two waves are same

ANSWER: Magnitudes of the two waves are same but phase difference is 90 °

(7) Which one of the following statement is valid for volume integral of a volume?

(A) Double integral of volume
(B) Triple integral of volume
(C) Integral of volume
(D) Integral of weight

(8) The value of VSWR is taken as 8 when the line is

(C) Open circuited
(D) Short circuited

(9) Let the coefficient of rejection be ρ, the value of VSWR will be l

(A) 1 - | ρ | / 1 + | ρ |
(B) 1 + | ρ | / 1 - | ρ |
(C) 1 + | ρ |² / 1 - | ρ |²
(D) 1 – | ρ |² / 1 + | ρ |²

ANSWER: 1 + | ρ | / 1 - | ρ |

(10) Main reason to prefer short circuited stub to open circuited stub is

(A) Open circuited stubs are liable to radiate
(B) Open circuited stubs have different characteristic impedance
(C) Open circuited stubs are complex in nature
(D) None of the above

(11) Inversion of impedance is achieved by the use of

(A) Balun transformer
(B) Full wave line
(C) Half wave line
(D) Quarter wave line

(12) Consider a transmission line with characteristic impedance Z?. This transmission line is terminated in Zo. The input impedance is

(A) 4 Zo
(B) 2 Zo
(C) Zo
(D) Zo /2

(13) Let Ev and Ey be the components of electromagnetic wave at 45 ° phase apart. This electromagnetic wave is traveling in x direction. The wave can be termed as

(A) Horizontally polarized
(B) Elliptically polarized
(C) Linearly polarized
(D) Circularly polarized

(14) The angle for which there is no reflection and the incident wave is vertically polarized, is known as

(A) Reflection angle
(B) Brewster angle
(D) None of the above

(15) For transmission line matching over a range of frequencies, it is best to use a

(A) Double stub
(B) Single stub of adjustable position
(C) Balun

For questions 16 and 17 refer to the data given below:

Consider the low loss transmission line. It has a characteristic impedance of 100 ohm connected to a load of 200 ohm.

(16) The voltage reflection coefficient is

(A) 1/5
(B) 1/4
(C) 1/3
(D) 1/2

(17) The standing wave ration is

(A) 5
(B) 4
(C) 3
(D) 2

(18) The transmission line for which capacitance per meter will be least is

(A) Coaxial cable
(B) Open wire line
(D) None of the above

(19) In a standing wave pattern, the phase angle corresponding to λ /4 is

(A) 190 °
(B) 140 °
(C) 90 °
(D) 180 °

(20) In a wave guide, the wavelength of a wave

(A) Is inversely proportional to the phase velocity
(B) Is greater than in free space
(C) Is directly proportional to the group velocity
(D) Depends on the wavelength dimension and the free space wavelength

ANSWER: Is inversely proportional to the phase velocity

(21) In a transmission line, refection will be zero if it is terminated by an impedance

(A) Equal to twice the characteristic impedance
(B) Equal to characteristic impedance
(C) Less than characteristic impedance
(D) None of the above

(22) There will be no distortion in telegraph when

(A) L/C = R/G
(B) C/L = R/G
(C) L/C = G/R
(D) None of the above