In automotive electronics, this is how often an event happens per second. For example, mains AC supply in Ireland has a frequency of 50 Hz. This means the supply alternates 50 times per second.

We know that in a DC circuit, electrons move in one direction only:

We also know that in an AC circuit, rather than flow constantly in one direction, the electrons move rapidly back and forth. The rate at which these electrons move back and forth is referred to as the frequency of the supply. In Ireland, the mains AC supply has a frequency of 50 Hz. In other words, the electrons in our homes move back and forth in the wires 50 times every second when a circuit is closed.

To calculate the frequency, we use the formula:

f=1sec/T, where f is the frequency in Hertz, and T is the cycleperiod in seconds.

Take the example of a signal that completes one cycle in 13.4 ms. To find the frequencey, we put the values into our formula: