Series circuits

Jonny Nelson introduces an animated explanation of circuits

In series circuits, electrical components are connected one after another in a single loop.

Circuit rules

An electron will pass through every component on its way round the circuit. If one of the bulbs is broken then current will not be able to pass round the circuit. If one bulb goes out, they all go out.

Current in series

A series circuit diagram with two lamps and three ammeters

A series circuit is one loop; all electrons in that loop form one current. An ammeter will measure the same current wherever it is placed in the circuit:

I_{1} = I_{2} = I_{3}

This is when:

current (I) is measured in amps (A)

If the resistance of any component in a series circuit changes, this will change the value of the current in the circuit.

Potential difference in series

The current will transfer energy from the power supply to the components in the circuit. Since energy has to be conserved, all of the source energy is shared between the components. Since potential difference is used to measure changes in energy, the potential difference supplied is equal to the total of the potential differences across all other components:

Circuit containing a switch, battery and two resistors labelled R1 and R2 in series. There are voltmeters in parallel to the resistors and battery.

V_{s} = V_{1} + V_{2}

This is when:

potential difference (V) is measured in volts (V)

If the resistance of any component in a series circuit changes, this will change the potential difference across all of the components.