# Alternating Current and Voltage MCQ Questions & Answers

Alternating Current and Voltage MCQs : This section focuses on the "Alternating Current and Voltage". These Multiple Choice Questions (MCQs) should be practiced to improve the Alternating Current and Voltage skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

What is the fourth harmonic of a fundamental frequency of 400 Hz?

A. 100 Hz
B. 4 kHz
C. 4 Hz
D. 1.6 kHz

Question 2

What is the average voltage when a rectangular wave's base line voltage is 20 V, its peak-to-peak voltage is 50 V, and its duty cycle is 20%?

A. 26 V
B. 30 V
C. 40 V
D. 45 V

Question 3

A half-cycle average voltage of 12 V is equal to what rms voltage?

A. 13.33 V
B. 8.48 V
C. 18.84 V
D. 7.64 V

Question 4

What is the instantaneous peak voltage at 250° on a 6 V peak sine wave?

A. +5.64 V
B. –5.64 V
C. +26.13 V
D. –26.13 V

Question 5

The effective value of a sine wave is equal to

A. 0.707 of peak voltage
B. 0.636 of peak voltage
C. sin 45° of peak voltage
D. both 0.707 of peak voltage and sin 45° of peak voltage

Question 6

Most practical alternators generate electricity from

A. a coil rotating within a magnetic field
B. a magnetic field rotating around fixed windings
C. a permanent magnet rotating within a varying electromagnetic field
D. none of the above

Question 7

A single-phase induction motor

A. is self-starting
B. operates at a fixed speed
C. is less reliable than a three-phase synchronous motor
D. none of the above

Question 8

In both induction and synchronous ac motors

A. the operating speed is very steady
B. the stator magnetic field is stationary
C. the stator magnetic field rotates
D. the "squirrel cage" forms the rotor

Question 9

A rectangular wave that has a duty cycle of 50% could be called a

A. "c" wave
B. sawtooth wave
C. square wave
D. triangular wave