A battery is a device that produces electricity by chemical action. It contains more than one cell. Each cell produces its own current. Batteries with several cells are used to provide electricity for automobiles, heavy equipments, space crafts, submarines and emergency electric lights.
The battery which is used in a car is called a storage or wet battery. Storage or wet battery like car battery has a greater capacity and produce more electricity in comparison to other batteries. It can be recharged again and again in order to use for a considerably longer period. The first such battery was invented in 1859 by a French physicist, Gaston Plante.
Storage or accumulator batteries are of two types: acid accumulators and alkali accumulators. Lead-acid batteries consist of plastic or hard-rubber containers. These batteries are used in cars throughout the world. Each cell of this battery contains two sets of electrodes. The pairs are suspended in dilute sulphuric acid. One electrode is positive and the other negative. One electrode is made of spongy lead and the other of lead dioxide. The separator plates keep them apart. This cell requires distilled water. Such a cell has a potential difference of 2 volts and the cells are connected in series. Most car batteries have 6 cells, giving 12 volts in all.
At the positive electrode, lead dioxide reacts with hydrogen and sulphate ions of sulphuric acid and forms lead sulphate and water. In this reaction, two electrons are obtained from the wires which balance the chemical reaction. At the negative electrode, lead reacts with sulphate ions and forms lead sulphate. This provides two electrons to the wire which maintains electrical balance. The net effect of this reaction is that electrons start flowing from the negative plate to the positive plate.
When the lead of lead dioxide is over, the cell stops working. This cell can be re-charged by making the electricity flow from the negative to the positive plate.
