## hpr3742 :: Battery

 A battery converts chemical energy into electrical energy by a
chemical reaction. Usually the chemicals are kept inside the battery. It
is used in a circuit to power other components. A battery produces
direct current (DC) electricity (electricity that flows in one
direction, and does not switch back and forth).
Using the electricity from an outlet in a building is cheaper and
more efficient, but a battery can provide electricity in areas that do
not have electric power distribution. It is also useful for things that
move, such as electric vehicles and mobile phones.
Batteries may be primary or secondary. The primary is thrown away
when it can no longer provide electricity. The secondary can be
recharged and reused.
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