battery

A battery stores chemical energy, which it converts to electrical energy. A typical battery, such as a car battery, is composed of an arrangement of galvanic cells. Each cell contains two metal electrodes, separate from each other, immersed within an electrolyte containing both positive and negative ions. A chemical reaction between the electrodes and the electrolyte, similar to that found in electroplating, takes place, and the metals dissolve in the electrolyte, leaving electrons behind on the electrodes. However, the metals dissolve at different rates, so a greater number of electrons accumulate at one electrode (creating the negative electrode) than at the other electrode (which becomes the positive electrode). This gives rise to an electric potential between the electrodes, which are typically linked together in series and parallel to one another in order to provide the desired voltage at the battery terminals (12 volts, for example, for a car battery). The buildup of charge on the electrodes prevents the metals from dissolving further, but if the battery is hooked up to an electric circuit through which current may flow, electrons are drawn out of the negative electrodes and into the positive ones, reducing their charge and allowing further chemical reactions.