Home » Alternating Current and Voltage Online Test » Alternating Current and Voltage Online Test – Multiple Choice Questions and Answers Alternating Current and Voltage Online Test – Multiple Choice Questions and Answers Posted on August 19, 2018January 4, 2016 by engineerLeave a comment 1. Most practical alternators generate electricity from a permanent magnet rotating within a varying electromagnetic field a coil rotating within a magnetic field a magnetic field rotating around fixed windings none of the above 2. What is the fourth harmonic of a fundamental frequency of 400 Hz? 1.6 kHz 4 Hz 4 kHz 100 Hz 3. The effective value of a sine wave is equal to 0.636 of peak voltage 0.707 of peak voltage sin 45° of peak voltage both 0.707 of peak voltage and sin 45° of peak voltage 4. 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%? 26 V 30 V 40 V 45 V 5. A half-cycle average voltage of 12 V is equal to what rms voltage? 8.48 V 7.64 V 18.84 V 13.33 V 6. A single-phase induction motor operates at a fixed speed is less reliable than a three-phase synchronous motor is self-starting none of these 7. In both induction and synchronous ac motors the operating speed is very steady the stator magnetic field rotates the “squirrel cage” forms the rotor the stator magnetic field is stationary 8. A pulse waveform has a high time of 8 ms and a pulse width of 32 ms. The duty cycle is 1% 25% 50% 100% 9. A rectangular wave that has a duty cycle of 50% could be called a triangular wave square wave sawtooth wave “c” wave 10. What is the instantaneous peak voltage at 250° on a 6 V peak sine wave? +5.64 V –26.13 V –5.64 V +26.13 V Loading … Question 1 of 10