In electricity, frequency refers to the number of times the alternating current (AC) switches between positive and negative in one second. It is measured in hertz (Hz), which is the unit of frequency. For example, if a current changes between positive and negative 60 times a second, it has a frequency of 60 Hz. The frequency of electrical current is typically used to describe electrical equipment operation.

Different countries have different frequencies that they use for their power grids. For example, in the US, the grid is based on a highly stable 60-hertz signal, meaning it cycles 60 times per second. In the UK, the frequency is 50 Hz.

The frequency of electrical current is important because it affects the operation of electrical equipment. For example, some equipment may be designed to operate at a specific frequency, and using it at a different frequency could cause it to malfunction or perform poorly.

In summary, Hz in electricity refers to the frequency of the alternating current, which is the number of times it switches between positive and negative in one second. Different countries have different frequencies for their power grids, and the frequency of electrical current is important for the operation of electrical equipment.