Matching batteries to bulbs


You can put batteries together to make a larger voltage. In this circuit the batteries are used to work the bulb. The bulb is called a component because it is a part of the circuit.
The bulb has 3V marked on its side. This means that it works best with a voltage of 3 volts. This voltage can be supplied by using two batteries which have 1.5V marked on their sides. This means that each battery gives a voltage of 1.5 volts but when they are put together they add up to give a voltage of 3 volts. This matches the voltage that the bulb needs to work best.

Why is the push of electricity measured in volts?
This measurement is named after Alessandro Volta who invented the battery in 1800.

What is the voltage of the mains?
The voltage of the mains in the United Kingdom is 240 volts. This is high enough to kill people, so mains electricity must always be treated with care.

What voltage bulb do you need to match the mains?
You need bulbs which have 240V written on them.

Is the voltage of the mains the same in every country?
No. In North America for example it is 110 volts. The voltage of the mains in countries in southern Europe is slightly different from the mains voltage of countries in Northern Europe. It's all very complicated.

When I am travelling overseas can I just plug my mains equipment into the sockets of the hotel?
Probably not. Not only might the voltage be different, but the sockets will also be of a different design.

To get over the different designs of plugs and sockets you can buy an adaptor, but if the voltages are different you won't be able to use the equipment even if you have an adaptor unless there is a device inside the equipment that will allow it to work with different voltages. If there is, the instruction book will tell you.


Do different kinds of battery have the same chemicals in them?
No. The most common batteries use zinc and carbon in a paste. This gives a voltage of 1.5V.


The small batteries that are used in watches have mercury in them. This gives a voltage of 1.35V.
Car batteries have lead and acid in them. This gives a voltage of 12V.

What happens when all the chemicals have been worked out?
The battery has no power to produce electricity. It has zero voltage and no current can flow from it.

Can the chemicals be altered to make the battery work again?
Most batteries must be thrown away when they have lost their power. Some batteries called rechargeable batteries have chemicals which can be charged to make the battery work again. These batteries can be recharged by using a special device which plugs into the mains and sends the correct kind of electricity through them.