Which device furnishes the electrical energy used by the load?

The source is the component that provides the electrical energy necessary for the load to operate. In an electrical circuit, the load represents the device that consumes power, such as a light bulb or motor, but it relies on the source for its energy. The source can be a battery, generator, or any other device that generates or supplies electrical energy.

By contrast, a switch is used to control the flow of electricity in the circuit but does not supply energy itself. Wires serve as the pathways for the electrical current to travel between the source and load but again do not provide energy. The load, while essential for the operation of the circuit, does not generate or supply electrical energy; its purpose is to utilize the energy supplied by the source. Therefore, the source is correctly identified as the device that furnishes the electrical energy used by the load.