Circuit and its Elements
Current moves from a point of high potential energy to a one of low potential. It can only do so if there is a path for it to follow. This path is called an electric circuit. All circuit contain four elements: a source, a load, a transmission system and a control.
The source provides the electromotive force. This established the difference in potential which makes current flow possible. The source can be any device which supplies electrical energy. For example, it may be a generator or a battery.
The load converts the electrical energy from the source into some other forms of energy. For instance, a lamp changes electrical energy into light heat. The load can be any electrical device.
The transmission system conducts the current round the circuit. Any conductor can be part of a transmission system. Most systems consist of wires. It is often possible, however, for the metal frame of a unit to be one section on its transmission system.
The control regulates the current flow in the circuit. It may control the current by limiting it, as does a rheostat, or by interrupting it, as does a switch.