What are the two requirements for a circuit?

• A. A source
• B. A source and a complete path
• C. A load and a conductor
• D. A switch and a fuse

Answer: (B)

A circuit needs energy to move electrons and a closed path for that energy to travel back to the source. The energy source provides the push that drives current, while a complete conducting path—wires and components that form a loop—lets the current flow continuously back to the source. If either part is missing, current cannot flow: a source without a loop has nowhere for electrons to go, and a loop without a source has no driving energy. A load and a conductor describe parts of a circuit, but without a source there’s no power to drive them. Switches and fuses play protective or control roles; they can interrupt or enable a path, but they don’t define the circuit by themselves. Therefore, the two requirements are a source of energy and a complete path.