How does an ohm meter determine resistance?

• A. By applying a small test current and measuring voltage drop
• B. By applying a voltage and measuring current
• C. By measuring temperature rise
• D. By counting electrons per second

Answer: (A)

An ohm meter finds resistance by injecting a small, known current into the unknown path and measuring the voltage that appears across it. Using Ohm's law, R = V / I, the meter uses the fixed test current and the measured voltage to calculate the resistance. This small current keeps testing safe for components and works even when the circuit isn’t powered by an external source, since the meter provides its own current from its internal battery. In practice, many meters implement a constant current source and measure voltage to compute resistance.

The other ideas don’t give a direct resistance value in the standard meter setup: applying a voltage and measuring current would work in theory, but handheld meters typically rely on a known current and voltage measurement; measuring temperature rise isn’t related to resistance in a simple, direct way; counting electrons per second isn’t how resistance is determined.