Which instrument is used to measure electrical resistance?

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

Answer: (C)

Resistance is determined by applying a known current and measuring the resulting voltage drop, then using Ohm’s law to compute R. An ohmmeter is built specifically for this task: it injects a small current through the unknown component and displays the resistance directly in ohms.

Ammeter and voltmeter measure different quantities—current and voltage, respectively—while a multimeter can measure multiple quantities, including resistance, but the instrument dedicated to measuring resistance is the ohmmeter.

Always ensure the circuit is de-energized and the component is isolated before measuring resistance. If the reading is very high or shows as infinite, the path is open; a very low reading indicates a near-short or a component with very low resistance.