50hz means action, speed and frequency, that is, 1 second 50 times. The household electricity in China is 50 Hz with a period of 0.2 seconds, that is to say, the positive and negative polarity of 220V changes once every 0.2 seconds and changes 50 times a second, which is 50 Hz.

Hertz overview:

Hertz is abbreviated as Hz. The physical unit of measuring frequency refers to the number of periodic fluctuations per second. The measurement units of high frequency mainly include kHz (i.e. 1000Hz), MHz (i.e. 1000kHz), GHz (i.e. 1000MHz) and THz (i.e. 1000GHz).

Heinrich? Rudolph? German physicist Hertz (1857~ 1894) first proved the existence of electromagnetic waves by experiments in 1887, and published a paper in 1888. He made great contributions to electromagnetism, so the international unit of frequency Hertz was named after him.

Hertz experiment proves that electromagnetic wave exists, and its propagation speed is equivalent to the speed of light. Hertz experiment has opened up an innovative road for the development of radio electronic technologies such as radio, radar and television. He studied the influence of ultraviolet light on spark discharge and found photoelectric effect from it. He thought that an object can release electrons under the irradiation of light, and this discovery became the basis for Einstein to establish the quantum theory of light.