### Electronics and Communication Engineering - Electromagnetic Field Theory MCQs Part 4

1.Which of the following laws of electromagnetic theory is associated with the force experienced by two loops of a wire carrying currents?

A. Maxwell's law
B. Coulomb's law
C. Ampere's law
D. Laplace's law

2.The intrinsic impedance of free space

A. increases with increase of frequency
B. decreases with increase of frequency
C. is independent of frequency
D. none

3.To couple a coaxial line to a parallel to wire line it is best to use a

A. slotted line
B. balun
C. directional coupler
D. quarter wave transformer

4.The shunt admittance of a transmission line is given by

A. γ = R + jωL
B. γ = R - jωL
C. γ = G + jωC
D. γ = jωGC

5.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

6.If short-circuited and open circuited impedances are 5 ohms and 20 ohms, then characteristic impedance is

A. 1 ohms
B. 10 ohms
C. 25 ohms
D. 100 ohms

7.Electric lines of force do not cross each other because

A. the lines of force mutually repel each other
B. the lines of force emanate from a point charge
C. the tangent to the line of force gives the direction of E and if they cross two tangents for E which is not possible
D. none of the above

8.A person with a receiver is 5 km away from the transmitter. What is the distance that this person must move further to detect at 3 dB decrease in signal strength?

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

A. γ = a + jβ
B. γ = jβ
C. γ = a
D. a = β = 0

10.SHF range is

A. 30 - 300 MHz
B. 300 - 3000 MHz
C. 3000 - 30000 MHz
D. 30000 - 300000 MHz