Why does a battery supply power? (Glossary)

Large amounts of energy are consumed in the production of chemicals that are then bound in the substances and can be released again. One example are hydrochloric acid and soda lye. Both substances are manufactured with a lot of energy input. If you then pour them together (very carefully!) they generate a lot of heat and react to form common salt and water.

The important parts of a battery also contain such bound energy and if, for example, the components of the Voltaic pile (Zinc and Copper as Electrodes, lye as the Electrolyte) are mixed in a fine distribution, heat is produced.

But in order to obtain electrical energy instead of heat, a trick is used whereby the overall chemical reaction is split spatially into single reactions: the copper is submerged in the lye on one side, the zinc on the other and both metals do not come into contact with each other.

But this trick does not initially work because electrons have to be exchanged between the partial reactions so that they can take place. The reaction at the copper electrode supplies 2 excess electrons, the reaction at the zinc electrode needs 2 electrons.

Beforehand, when mixed in a fine distribution, the electron exchange was possible since the substances were in direct contact with each other. The partial reactions cannot take place on account of the spatial gap and the fact that the lye is not conductive for electrons (though it is conductive for an electric charge in the form of ions). At one end there are too many electrons that have to be 'removed', at the other end they are missing.

Metals are conductive for electrons, including the two electrodes used of copper and zinc. So what could be more obvious than to join the two electrodes with a cable? Voila - the electrons, in other words electric current, flow from one electrode the other, and the chemical reactions can continue to take place in the electrolyte soup.

We can then make this current work. The available Voltage and power depends on the battery design. As soon as the electrical connection between the electrodes is interrupted - when we switch our device off - the chemical reactions inside the battery once again (almost) come to a standstill.

© Marc Stenzel

	See also:
		Glossary overview Batteries - Accumulators - Cells (Glossary) Fuel Cells (Glossary) Battery-Packs

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