Which device is used to measure resistance by applying a test current and reading voltage drop?

Which device is used to measure resistance by applying a test current and reading voltage drop?

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

Answer: (B)

Measuring resistance by applying a test current and reading the voltage drop requires an instrument that sources a known current through the unknown and senses the resulting voltage. That’s exactly what an ohmmeter does: it provides a small internal current, measures the voltage across the resistance, and computes R = V/I (often displaying it directly). A voltmeter, on the other hand, only measures voltage and doesn’t inject current, so it can’t determine resistance by itself. An ammeter measures current (in series) but doesn’t determine resistance without knowing the voltage. A wattmeter measures power, not resistance.

Measuring resistance by applying a test current and reading the voltage drop requires an instrument that sources a known current through the unknown and senses the resulting voltage. That’s exactly what an ohmmeter does: it provides a small internal current, measures the voltage across the resistance, and computes R = V/I (often displaying it directly). A voltmeter, on the other hand, only measures voltage and doesn’t inject current, so it can’t determine resistance by itself. An ammeter measures current (in series) but doesn’t determine resistance without knowing the voltage. A wattmeter measures power, not resistance.