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how does a battery hold its power source
Mack- Batteries start off with stored chemical energy. In other words, they can lower their energy if the chemicals in them recombine into different forms. (actually, what's involved is something called "free energy", not simple energy, but you can put off thinking about that until you get a chance to study this in more depth.) In order for the chemicals to reach a lower-energy state (say by plating copper out of solution while zinc dissolves), electrons have to flow from one part to another, driving the external circuit. Once the chemicals have settled into the lower energy state, the battery is dead. Some types of batteries can then be recharged by forcing electrical current through them backwards, pulling the chemicals back to their starting states.
You might search further on this site for "battery" or "batteries" to fet more information on some specific types.
(republished on 07/13/06)
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