Which instrument indicates if a circuit is open or closed when no current is flowing?

The continuity tester is specifically designed to determine whether an electrical circuit is open or closed, especially when no current is flowing. It works by sending a small current through the circuit. If the circuit is closed (complete), the current will pass through, and the tester will indicate continuity, usually with a light or a sound. Conversely, if the circuit is open (incomplete), no current will flow, and the tester will indicate a lack of continuity.

This tool is particularly useful for troubleshooting electrical systems, as it allows technicians to quickly assess whether the path is intact and can verify connections without needing a live current. Unlike a multimeter, which can perform a variety of measurements including voltage and resistance, the continuity tester is focused solely on this aspect, making it straightforward and effective for this purpose.