Batteries

Sometimes, you don't want to use a cord to plug a clock or CD player into an electrical outlet. You want electricity to be portable, or easy to carry around. Batteries are one way to make electricity portable. Electricity from batteries can operate clocks, CD players, and other machines just about anywhere.

A battery has two different metals and an acid solution inside it. A chemical reaction involving the two metals and the acid solution generates an electrical current. The electrical current travels through a circuit into the machine. If you don't turn the machine off, the battery wears down. The chemical reaction gets weaker and weaker until the battery no longer produces enough electricity to run the machine. That's when you need to put in a new battery.