### Ac and DC supply

#### DC that is Direct Current

Many of the things we use at home need a DC supply but the supply to our houses is AC, so what's the difference?

A cell or a battery (a group of cells) supply direct current. If we connect a battery to an oscilloscope we can see a graph of the change in potential difference (voltage) with time. The graph we see is a horizontal line. The potential difference is steady and in one direction. If the battery is connected to a circuit a steady current will flow in one direction.

#### AC that is Alternating Current

If we connect it to an oscilloscope to the live and neutral of a mains supply to see a graph of potential difference (voltage) plotted against time then the graph rapidly moves up and down. The potential difference changes from one direction to the other many times per second in a sinusoidal pattern. In the UK there are 50 complete changes every second (50Hz).

The potential difference is applied to the live wire. The current is “pushed and pulled” from the live wire, the neutral wire completes the circuit.