If the electrical supply is 60 Hz, what is the period of one cycle in seconds?

• A. Approximately 0.0167 s (16.7 ms).
• B. Approximately 0.0333 s (33.3 ms).
• C. Approximately 0.0083 s (8.3 ms).
• D. Approximately 0.1 s (100 ms).

Answer: (A)

The period is the time for one complete cycle. Frequency tells how many cycles occur in one second, so the period is the reciprocal of the frequency: T = 1/f. With a 60 Hz supply, the period is 1/60 seconds, which equals about 0.016666... seconds. That rounds to 0.0167 s, or 16.7 milliseconds. So one cycle takes roughly 0.0167 seconds. Other options correspond to different frequencies: 0.0333 s is 1/30 Hz, 0.0083 s is 1/120 Hz, and 0.1 s is 1/10 Hz.