Key Stage 3 (KS3) Physics Practice Test

For electricity to flow in a circuit, there must be a complete path for the current to travel through and a power source that provides the necessary energy. A complete path, often referred to as a closed circuit, ensures that electrons can move uninterrupted from the power source, through the circuit components, and back to the power source. This flow of electrons is what constitutes electric current.

The power source, such as a battery or generator, is essential as it creates the potential difference that drives the current through the circuit. Without either of these components—an unbroken path and a power source—electricity cannot flow, rendering the circuit incomplete.

While the other choices mention various components that may be present in a circuit or aspects that facilitate the operation of an electrical device, they do not encapsulate the fundamental requirements needed for electrical current to actually flow. Thus, the combination of a complete path and a power source is crucial for electricity to move through a circuit.