Which device is used to determine whether AC electricity is present in a circuit?

• A. Circuit tester
• B. Multimeter
• C. Ohmmeter
• D. Ammeter

Answer: (A)

To know whether AC power is present in a circuit, you want a quick, safe indication of voltage. A circuit tester is designed for this purpose: it provides an immediate yes/no signal that the circuit is live, often with a light or beep, and many models are non-contact, meaning you don’t have to touch conductors to verify presence. This makes it ideal for safety checks before you touch anything.

A multimeter can also detect AC voltage by measuring the voltage level, but it requires selecting the correct mode, setting the range, and connecting probes properly, which takes more steps and increases the chance of mistakes in a live situation. The ohmmeter is used to measure resistance and is used on de-energized circuits, not to determine whether power is present. An ammeter measures current, not whether voltage exists, so it doesn’t indicate live status.

So, for a quick check to confirm if AC is present, the circuit tester is the best tool.