# Electromagnetic Theory Questions and Answers – Waveguide Current and Excitation

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This set of Basic Electromagnetic Theory Questions and Answers focuses on “Waveguide Current and Excitation”.

1. The source voltage of a 75ohm transmission line is given by 150V. Find the load current.
a) 0.5
b) 2
c) 4
d) 1

Explanation: The load current is given by IL = VS/Z0. On substituting for VS = 150 and Z0 = 75, we get IL = 150/75= 2A.

2. The guided terminations are used to
a) Increase reflection
b) Increase transmission
c) Eliminate reflection loss
d) Eliminate attenuation

Explanation: The guided termination refers to the waveguide shorted by conducting plates. This is done in order to eliminate the reflection losses.

3. Which type of wave does the resonant cavity produce?
a) Standing waves
b) Guided waves
c) Transmitted waves
d) Attenuated waves

Explanation: Resonant cavity is the waveguide shorted by a conducting plate. This is to reduce the reflection losses. Such arrangement leads to standing waves.

4. Which of the following parameter cannot be calculated from the standing waves?
a) Peak voltage and peak current
b) SWR
c) Reflection and transmission coefficients
d) Attenuation constant

Explanation: The peak voltage and current can be directly measured from the standing waves. The standing wave ratio, reflection coefficient and the transmission coefficient can also be calculated from it. Only the attenuation constant cannot be calculated directly.

5. For efficient transmission, the characteristic impedance of the transmission line has to be
a) 50 ohm
b) 75 ohm
c) Either 50 or 75 ohm
d) Neither 50 nor 75 ohm

Explanation: Generally, for ideal transmission lines, the characteristic impedance should be either 50 ohm or 75 ohm.

6. The cavity resonators are used in the klystron amplifiers for
a) Amplifying RF signals
b) Amplifying microwave signals
c) Attenuating RF signals
d) Attenuating microwave signals

Explanation: The cavity resonators are employed in the klystron amplifiers for amplifying the microwave signals.

7. The cavity resonators used in the reflex klystron oscillators are for
a) Generating RF signals
b) Generating microwave signals
c) Amplifying RF signals
d) Amplifying microwave signals

Explanation: Oscillators are devices that generate signal waveforms. The reflex klystron oscillator is used to generate microwave signals.

8. One of the applications of the cavity resonators is duplexer in RADAR systems. State true/false.
a) True
b) False

Explanation: Cavity resonator is used in duplexers of RADAR systems, as resonant cavity in transmit receive (TR) tubes and antitransmit receive (ART) tubes.

9. Cavity wave meters are used to measure which parameter of the wave?
a) Wavelength
b) Reflection factor
c) Phase
d) Frequency

Explanation: Cavity resonators are used in cavity wave meters for the measurement of frequency of the microwave signals.

10. The waveguides are terminated by the procedure of
a) Trimming
b) Polishing
c) Tapering
d) Pruning 