Frequency

Frequency counts full cycles per second, measured in hertz (Hz). A 50 Hz sinusoidal mains waveform completes 50 cycles each second and reverses current direction twice per cycle—100 reversals per second. 60 Hz gives 120 reversals per second.

Frequency is closely tied to its cousin period — the time for one cycle. They’re reciprocals: period = 1 / frequency. So 50Hz means each cycle takes 1/50 = 0.02 seconds (20 ms). Higher frequency means shorter, faster cycles.

The idea turns up everywhere once you notice it: the pitch of a buzzer (higher Hz = higher note), a radio station’s channel, a screen’s refresh rate, and a processor’s clock speed. Bigger units keep the numbers manageable: 1 kHz = 1000 Hz, 1 MHz = 1,000,000 Hz, 1 GHz = a billion Hz.