CIRCUITS AND CONDUCTORS
QCA Unit number 4F

WHAT'S THE BIG IDEA?

Electricity flows round a full circuit, often doing work as it goes. Electricity is not 'in' a battery - but the battery provides the push that drives the electricity round the circuit. It's like a pump that shoves the electricity round. Big pumps give big shoves. The shove from the mains is strong enough to kill you. But the push from a torch battery is tiny. If you really want to shock yourself, you can put a delicate bit of your anatomy - like your tongue - to the torch battery and feel a tingle. But don't try that with a car battery - which gives a much bigger push and will give your arms a jolt if you touch the terminals.

A circuit is a continuous ring of conductors - materials that let electricity through them easily. You're not a good conductor - though you are a better conductor if you are wet - but metals are brilliant at the job, conducting electricity with ease. That's why we use them for wires and switches.

Electricity that sneaks round the circuit without doing any work is called a short circuit. Joining the terminals of a battery with a wire is a short circuit, and it wastes the electricity, which will heat up the wire.

Most electricity does some work on the way - lighting bulbs, ringing bells, buzzing buzzers or spinning motors - and the more things it has to do, the weaker its effort with each. Adding lots of bulbs to an ordinary circuit is a sure way of getting a row of very dim lights.