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Electric current and voltage

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Series & parallel circuits

There are two types of circuit we can make, called series and parallel.

The components in a circuit are joined by wires.

  • if there are no branches then it's a series circuit

  • if there are branches it's a parallel circuit

Series circuits

In a television series, you get several episodes, one after the other. A series circuit is similar. You get several components one after the other.

If you follow the circuit diagram from one side of the cell to the other, you should pass through all the different components, one after the other, without any branches.

Shows a circuit with a battery and two lamps connected in series.

If you put more lamps into a series circuit, the lamps will be dimmer than before.

In a series circuit, if a lamp breaks or a component is disconnected, the circuit is broken and all the components stop working.

Shows a circuit with a battery and two lamps connected in series. The second lamp has blown and the circuit is broken, so the first lamp doesn't light.

Series circuits are useful if you want a warning that one of the components in the circuit has failed. They also use less wiring than parallel circuits.

Parallel circuits

In parallel circuits different components are connected on different branches of the wire. If you follow the circuit diagram from one side of the cell to the other, you can only pass through all the different components if you follow all the branches.

Shows a circuit with a battery and two lamps connected in parallel

In a parallel circuit, if a lamp breaks or a component is disconnected from one parallel wire, the components on different branches keep working. And, unlike a series circuit, the lamps stay bright if you add more lamps in parallel.

Shows a circuit with a battery and two lamps connected in parallel. If either of the lamps blew, the other would stay lit because the circuit isn't broken.

Parallel circuits are useful if you want everything to work, even if one component has failed. This is why our homes are wired up with parallel circuits.

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