Types of Circuits - Open Circuits
An open circuit is a circuit where the path has been interrupted or "opened" at some point so that current will not flow. An open circuit is also called an incomplete circuit.
An open circuit could be intentional or un-intentional. An intentionally open circuit would be the circuit to the lights in the room that are turned off. There is no closed path available for the electricity to flow to the lights because the switch is in the "off" position which "opens" the path the electricity would normally flow through.
An example of a circuit that is un-intentionally open is when a circuit breaker operates due to too much current on the circuit and shuts the circuit off. The common electrical industry terminology would be to say that the circuit breaker or fuse "opened" or tripped the circuit. It did this by "opening" the switch in the circuit breaker.