Electronics-Alternating Current and Voltage
Electronics-Alternating Current and Voltage
1. In both induction and synchronous ac motors
- the operating speed is very steady
- the stator magnetic field is stationary
- the stator magnetic field rotates
- the "squirrel cage" forms the rotor
2. Most practical alternators generate electricity from
- a coil rotating within a magnetic field
- a magnetic field rotating around fixed windings
- a permanent magnet rotating within a varying electromagnetic field
- none of the above
3. A half-cycle average voltage of 12 V is equal to what rms voltage?
- 13.33 V
- 8.48 V
- 18.84 V
- 7.64 V
4. A rectangular wave that has a duty cycle of 50% could be called a
- "c" wave
- sawtooth wave
- square wave
- triangular wave
5. The effective value of a sine wave is equal to
- 0.707 of peak voltage
- 0.636 of peak voltage
- sin 45° of peak voltage
- both 0.707 of peak voltage and sin 45° of peak voltage
6. What is the fourth harmonic of a fundamental frequency of 400 Hz?
- 100 Hz
- 4 kHz
- 4 Hz
- 1.6 kHz
7. that 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