Which instrument is used to measure electrical resistance?

• A. Ohmmeter
• B. Voltmeter
• C. Coulometer
• D. Ammeter

Answer: (A)

Measuring resistance relies on Ohm’s law, which links voltage, current, and resistance. An ohmmeter is designed specifically for this task: it injects a small, known current through the unknown component (or applies a small voltage and measures the resulting current) and then computes and displays the resistance. This direct readout is what makes it the right tool for determining how much a component resists electrical flow.

A voltmeter measures voltage, not resistance, so it’s used to find the potential difference between two points. An ammeter measures current, typically in series with a circuit. A coulometer is used for measuring electric charge, not resistance in a basic circuit.