Batteries come in all shapes and sizes. Batteries are needed for many different purposes. Most torches, radios, calculators, cell phones, some toys and even cars, pacemakers and hearing aids need batteries to work.
Batteries are useful because they store chemical energy. When the battery is connected in an electrical appliance and the appliance is switched on, the stored energy in the battery is transferred to the appliance in the form of electrical energy to make it work.