An ohmmeter is used to measure

• A. Current
• B. Voltage
• C. Power
• D. Resistance

Answer: (D)

Measuring resistance relies on Ohm's law, which links voltage, current, and resistance. An ohmmeter is built to determine resistance by using its own internal source to push a small current through the component and then observe the response. By applying a known current and measuring the resulting voltage (R = V/I), or by applying a small voltage and measuring the current, the meter displays the resistance. This makes resistance the quantity being determined, rather than the actual current, voltage, or power in the circuit.

The other quantities are what separate instruments measure: a device designed to measure current reads the flow in series, a voltmeter measures the potential difference across two points, and power requires both voltage and current (P = VI).