Series and parallel
|This is a series circuit, showing the location of an ammeter and voltmeter.
The current is the same at all points along the circuit
The sum of the voltage across the individual components is equal to that at the power supply.
|At the junctions, the current splits, but then rejoins at the final junction.|
Voltage across each component stays the same
Parallel circuits are used in christmas lights because, if one light breaks, the electricity will flow the other route.
This is an important relationship between voltage, resistance and current. It is very simple and outlined in a triangle below, where V = IR; and some units are explained.