Electrical Cells and Batteries
In it's most simple form a battery can be regarded as a pump that provides the energy to move charge around a circuit. In order to provide a potential difference, or electro-motive (EMF) a store of energy is required. One such method is a battery or cell. The common usages of the term battery is any device that converts chemical energy into electrical energy. However, strictly speaking, the term battery is used when several electrical cells are connected together to provide a source of a potential difference in a circuit. If it is just a single chemical source then it is called a cell.
The first battery was invented in 1793 by Alejandro Volta. Just as the two different metals touching the wet skin of a frog's leg, caused an electrical current to flow, early batteries increased the voltage that could be produced by stacking a pile of discs made from silver and zinc sandwiched between paper soaked in a salt water solution as shown in Figure 2. In honour of Volta, we use the Volt as the unit of potential difference and EMF.