In terms of electricity, a closed circuit is basically one in which the flow of electrical current circulates among its components, which can be electrical power sources, switches, resistors, semiconductors, inductors, capacitors and cables, among others. Whilst an open circuit is one that is interrupted, this means there is an open switch and therefore no charges flow through it, that is, there is no flow of electrical current.
So, when the connections are properly made and a small desk fan is connected to the open wires in the circuit, if this is close, the electrical current will flow through the circuit and turns on the fan.
Now, if the wires are removed from the power source, the circuit will be open and the fan will turn off.
