According to the law of conservation of energy, energy can not be created nor destroyed but can be transformed from one form to another. Battery is a device that is able to store electrical energy in form of chemical energy. The chemical energy stored in a battery is transformed to electrical energy when wires are connected to the terminals of the battery due to flow of electrons. If the wires are connected to a bulb then the electrical energy in the wires is converted to heat energy and light energy by the bulb.