How many cycles per second does AC power have in the U.S.?

How many cycles per second does AC power have in the U.S.?

• A. 50
• B. 60
• C. 120
• D. 180

Answer: (B)

The main idea here is understanding how often the alternating current reverses direction in the U.S. electrical system. In the United States, the standard frequency is 60 hertz, meaning the AC waveform completes 60 full cycles every second. This 60 Hz rate is built into the national grid and influences how devices operate, from motors to clocks, because many timing and speed characteristics are set to match that frequency. Some other countries use 50 Hz; the choice between 50 Hz and 60 Hz is historical and affects performance of equipment designed for a specific frequency. The other numbers aren’t standard frequencies in U.S. power systems: 120 refers to typical household voltage (volts), not cycles per second, and 180 isn’t a standard electrical-frequency value.

The main idea here is understanding how often the alternating current reverses direction in the U.S. electrical system. In the United States, the standard frequency is 60 hertz, meaning the AC waveform completes 60 full cycles every second. This 60 Hz rate is built into the national grid and influences how devices operate, from motors to clocks, because many timing and speed characteristics are set to match that frequency.

Some other countries use 50 Hz; the choice between 50 Hz and 60 Hz is historical and affects performance of equipment designed for a specific frequency. The other numbers aren’t standard frequencies in U.S. power systems: 120 refers to typical household voltage (volts), not cycles per second, and 180 isn’t a standard electrical-frequency value.