Making a battery from cells

A torch usually holds more than one cell. Does the order matter? In Activity 3.3 you take the cells out of a two-cell torch, put them back in different orders, even turn one round, and check the lamp each time.

It glows only one way: when the positive terminal of one cell touches the negative terminal of the next. Turn one cell the wrong way round and the lamp stays dark. A TV remote with one cell put in backwards does not work either, for the same reason.

Two or more cells joined like this make a battery. More cells give the circuit more energy, or energy for a longer time, or both. A power bank is just many cells joined together inside one box.

Sometimes the cells sit side by side instead of end to end. Look inside the compartment: a thick wire or metal strip joins the positive terminal of one cell to the negative terminal of the next. + and − signs are printed inside to show you which way each cell goes.

One word that confuses people: we also say battery for a single cell. The 'battery' in a mobile phone is one cell.