Batteries store chemical energy and release it as electricity when connected in a circuit.

The longer version

Inside a battery, two different materials sit apart with a substance between them that lets ions pass but blocks electrons. Chemical reactions at one side release electrons, while reactions at the other side accept them. Prevented from taking the short route inside, the electrons travel through whatever is connected outside.

That outside journey is the current that powers a device. The reactions stop once the reacting chemicals are used up, and in some designs they can be driven backwards by supplying current. Voltage depends on the chemistry chosen, while the total stored energy depends on how much material is inside.

Where this entry sits

Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.