Batteries

Automobile Battery

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All batteries contain one or more cells. Electro-chemical devices that convert chemical

energy into electric energy. A cell has three main components :

1) a positive electrode (+),

2) a negative electrode (-), and

3) an electrolyte , which is in contact with both electrodes.

When the battery is connected in a circuit, chemical reactions occur that produce an excess

of electrons in the negative electrode and a deficit in the positive electrode. The electrons

flow around the external circuit. This movement of electric charge is balanced by a movement

of ions (other charged particles) through the electrolyte.

Cells can be divided into primary and secondary . Primary cells include alkaline long-life batteries,

typically used in flashlights, which generate power by slowly using up their own store of chemicals.

Secondary cells include the lead-acid batteries used in autombiles and NiMH (nickel metal hydride)

batteries used in cellular phone. Unlike primary cells, secondary cells can be re-charged by passing

a current through them in the reverse direction to that in which they normally cause a current to flow.

Fuel Cells

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Unlike a battery, which gradually loses its ability to generate electricity as the chemicals

inside it get used up, a fuel cell generates electricity from a continuous supply of chemicals.

Like a battery, a fuel cell has positive and negative electrodes and an electrolyte in between.

Fuel cells are used in unmanned space probes and in the Space Shuttle; they are expected

to be used in the cars of the future, because they are twice as efficient as internal combustion

engines and produce nothing more polluting than water.