In an electrical circuit, a cell or battery may be used to provide the electrons with electrical potential energy. They then move around the circuit from the negative to the positive terminals. As they leave the negative terminal, the electrons have a high electrical potential energy. When they meet a component, such as a lamp, some of that energy is transferred out as heat or light. The electrons return to the positive terminal with less energy. There is therefore a difference between the levels at negative and positive terminals. This difference is measured by the potential difference or voltage. The greater the voltage of a cell or battery, the more energy it is able to provide.