Which statement best describes an open circuit?

• A. A break in the circuit so the current cannot flow.
• B. A short circuit occurs when components touch across different voltages.
• C. A closed path that allows continuous current flow.
• D. A fault that increases resistance but still passes current.

Answer: (A)

An open circuit means there is a break in the conducting path, so current cannot flow. This is exactly what happens when a wire is broken or a switch is open—the loop isn’t complete, and electrons have nowhere to go, so the circuit is effectively inactive.

The other descriptions describe different conditions. A short circuit is when current takes an unintended, very low-resistance path and bypasses the load, which is the opposite of an open circuit. Describing a closed path that allows continuous current flow refers to a closed circuit, not an open one. A fault that increases resistance but still allows some current means the circuit isn’t fully broken; there’s still a path for current, so it’s not an open circuit either.

In alarm system terms, an open circuit is a broken loop that prevents the alarm signal from traveling around the circuit.