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A battery and a bulb

Electricity and magnetism · level 1, lesson 5 of 6

A question to start

You have a battery, a small bulb and two wires. How do you join them so the bulb lights up?

The idea

The electricity has to go all the way round: out of one end of the battery, along a wire, through the bulb, along the other wire and back into the other end of the battery.

That loop is called a circuit. If there is a gap anywhere, the electricity stops, and the bulb goes out.

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Worked examples

1. One wire. With only one wire, from the battery to the bulb, nothing happens. There is no way back.

2. A loose wire. Lift one wire off the battery. The bulb goes out at once. Put it back and the bulb lights again.

3. Two batteries. Two batteries in a line, + to −, make the bulb brighter. Too many could burn it out.

Try it

  1. What do we call the loop that electricity goes round?
  2. Why does one wire not light the bulb?
  3. What happens if a wire comes loose?
  4. A torch has a battery, a bulb and wires inside. Why does the torch need a button?
Answers
  1. A circuit.
  2. The electricity has no way back to the battery.
  3. There is a gap, so the bulb goes out.
  4. The button closes and opens the loop, so you can turn the bulb on and off.

Common mistake

"The electricity gets used up in the bulb." The electricity goes all the way round and back to the battery. What the bulb uses is the battery's energy.

Where it leads