A switch is an electronic component that can interrupt or divert the flow of current in a circuit. There are many different types of switches. The most familiar is a simple toggle switch, an example of which is a common household light switch. In a toggle switch, there are two states (open or closed) that are achieved by two different positions of the switch. In the closed position, electrical contacts of the switch are touching, allowing for electricity to flow. Conversely, in the open position, the contacts are separated and electricity cannot flow.

Switches can be operated by variables other than human input. For example, a thermostat is a common switch that operates based on temperature. Other methods for input can include pressure, force, voltage and current. As such, switches can be automatic, depending on the state of the input.

A wire is a conductor that is used to connect elements in a circuit. They carry electricity throughout the circuit and add very little resistance to the circuit.

A power supply supplies electrical energy to the circuit. There are many different types of power supplies, the most basic being a cell and the most familiar being the battery. Batteries are used to power small household circuits and they are made up of more than one cell. Cells and batteries convert chemical power into electrical power in order to provide energy to the circuit. Other types of power supplies include: solar cells, household power outlets, transformers, etc.