# ELECTRONICS IMPORTANT MCQ PDF-Antenna & Wave Propagation 3

1)   Which among the following exhibits perpendicular nature in TEM wave?
a. Electric field
b. Magnetic field
c. Direction of propagation
d. All of the above

2)   Which equations are regarded as wave equations in frequency domain for lossless media?
a. Maxwell’s
b. Lorentz
c. Helmholtz
d. Poisson’s

3)   If the magnetic field component of a plane wave in a lossless dielectric is H = 50 sin (2π x 106 t – 6x) az mA/m , what will be the wave velocity?
a. 1.047 x 106 m/s
b. 1.257 x 106 m/s
c. 2.50 x 106 m/s
d. 3 x 106 m/s

4)   In an electrical circuit,which nature of impedance causes the current & voltages in phase?
a. Reactive
b. Resistive
c. Capacitive
d. Inductive

5)   Which type of
ground wave travels over the earth surface by acquiring direct path
through air from transmitting to receiving antennas?

a. Surface wave
b. Space wave
c. Both a & b
d. None of the above

6)   After which phenomenon/phenomena do the waves arrive at the receiving antenna in ionospheric propagation?
a. Reflection or Scattering
b. Refraction
c. Defraction
d. All of the above

7)   By which name/s is an ionospheric propagation, also known as?
a. Sea wave propagation
b. Ground wave propagation
c. Sky wave propagation
d. All of the above

8)   According to
Snell’s law in optics, if a ray travels from dense media to rarer media,
what would be its direction w.r.t the normal?

a. Towards
b. Away
c. Across
d. Beside

9)   Which mechanism/s is/are likely to occur in mid-frequency operation corresponding to ionospheric region?
a. Only Reflection
b. Only Refraction
c. Partial reflection & refraction
d. None of the above

10)   Which among
the following plays a primary role in generation of conduction current
in an ionosphere due to presence of electric field?

a. Ions
b. Motion of electrons
c. Neutral molecules
d. None of the above

11)   Which type of wire antennas are also known as dipoles?
a. Linear
b. Loop
c. Helical
d. All of the above

12)   Which antennas are renowned as patch antennas especially adopted for space craft applications?
a. Aperture
b. Microstrip
c. Array
d. Lens

13)   Which conversion mechanism is performed by parabolic reflector antenna?
a. Plane to spherical wave
b. Spherical to plane wave
c. Both a and b
d. None of the above

14)   Which
antenna radiating region/s has/have independent nature of angular field
distribution over the distance from the antenna?

a. Reactive near-field region
b. Fresnel region
c. Fraunhofer region
d. All of the above

15)   Sterdian is a measurement unit of __________
a. Point angle
b. Linear angle
c. Plane angle
d. Solid angle

16)   According to the geometry, how many sterdians are present in a full sphere?
a. π/2
b. π
c.
d.

17)   The vector magnetic potential shows the inverse relationship with its ____
a. Source
b. Distance of point from the source (R)
c. Both a and b
d. None of the above

 ANSWER: Distance of point from the source (R)
18)   In retarded potentials, what factor of time delay is generally introduced in A & V equations?
a. R + c
b. R – c
c. R/c
d. R x c

19)   In the
solutions of inhomogeneous vector potential wave equation, which
component exists if the source is at origin and the points are removed
from the source (Jz = 0)?

a. Inward
b. Outward
c. Both a and b
d. None of the above

20)   If a half-wave dipole operates at 300 MHz with λ = 0.5m & D0 = 1.643, what will be its effective area?
a. 0.032 m2
b. 0.047 m2
c. 0.65 m2
d. 0.99 m2

21)   Dipole
antenna is symmetrical in nature where the two ends are at equal
potentials with respect to _____point

a. Initial
b. Eventual
c. Mid
d. None of the above

22)   Which term
is regarded as an inductive field as it is predictable from Biot Savart
law & considered to be of prime importance at near field or the
distance close to current element?

a. 1/ r
b. 1/ r2
c. 1/ r3
d. 1/ r4

23)   What is the nature of current distribution over the small dipoles?
a. Spherical
b. Rectangular
c. Triangular
d. Square

24)   For
receiving a particular frequency signal, which tuning component must be
used by the loop to form a resonant circuit for tuning to that
frequency?

a. Capacitor
b. Inductor
c. Resistor
d. Gyrator

25)   If the
radius of loop is λ/ 20 in a free space medium,what will be the
radiation resistance of 8-turn small circular loop?

a. 0.7883 Ω
b. 50.45 Ω
c. 123.17 Ω
d. 190.01 Ω

26)   What is the far-field position of an electric short dipole?
a. Along x-axis
b. Along y-axis
c. Along z-axis
d. Along xy plane

27)   What would happen if the rms value of induced emf in loop acquires an angle θ = 90°?
a. Wave is incident in direction of plane of the loop with induced maximum voltage
b. Wave is incident normal to plane of the loop with no induced voltage
c. Wave is incident in opposite direction of plane of the loop with minimum voltage
d. None of the above

 ANSWER: Wave is incident normal to plane of the loop with no induced voltage
28)   If a linear
uniform array consists of 9 isotropic elements separated by λ/4, what
would be the directivity of a broadside array in dB?

a. 6.53 dB
b. 7.99 dB
c. 8.55 dB
d. 9.02 dB

29)   If the
elements of a binomial array are separated by λ/4, how many shape
patterns are generated with no minor lobes?

a. 2
b. 4
c. 8
d. 16

30)   What kind of beamwidth is/are produced by Chebyshev arrays for given side lobe level (SLL)?
a. Widest
b. Narrowest
c. Both a and b
d. None of the above

31)   If the length of elements of an array is greater than λ/2, which will be the operating region of an array?
a. Transmission line region
b. Active region
c. Reflective region
d. All of the above

32)   Which angle of rhombic antenna represents one half of included angle of two legs of one wire?
a. Apex angle
b. Tilt angle
c. Both a and b
d. None of the above

33)   Which among the following is not a disadvantage of rhombic antenna?
a. Requirement of large space
b. Reduced transmission efficiency
c. Maximum radiated power along main axis
d. Wastage of power in terminating resistor

34)   Why are beverage antennas not used as transmitting antenna?