TOPIC 1: ALTERNATING VOLTAGES AND CURRENT

In North America, the frequency of ac utility  voltage is 60 Hz. The period is

• 8.3 ms

• 16.7 ms

• 60 ms

• 60 s

The amplitude of a sine wave is measured ..

• at the maximum point

• between the minimum and maximum points

• at the midpoint

• anywhere on the wave

A sine wave reaches maximum positive voltage at:

• 90°

• 0°

• –90°

• 360°

If an alternating current is represented by i=10 sin 314 t, where t is in seconds, then its frequency is around :

• 40Hz

• 50Hz

• 60Hz

• 70Hz

The instantaneous value of alternating voltage is

• peak value

• average value

• rms value

• instantaneous value

Give the suitable sinusoidal equation for waveform V1 above

• V1 = 30 sin ωt

• V1 = 30 sin ωt - 45°

• V1 = 30 sin ωt + 45°

• V1 = 30 sin ωt ± 45°

For the waveform shown, the same power would be delivered to a load with a dc voltage of

• 21.2 V

• 37.8 V

• 42.4 V

• 60.0 V

Convert the angle of 3π/5 radian to degree unit.

• 180°

• 118°

• 108°

• 110°