When measuring the resistance of a circuit, power must be removed from the circuit.

When measuring the resistance of a circuit, power must be removed from the circuit.

• A. True
• B. False
• C. Not sure
• D. Sometimes

Answer: (A)

Measuring resistance with a meter works by sending a small test current through the path and reading the resulting voltage. This only yields a true DC resistance when the circuit is passive, with no active power sources influencing it. If power is present, the circuit already has currents and voltages that interfere with the meter’s test signal, producing an inaccurate reading and potentially risking damage to the meter or components. So, to get a valid resistance measurement, you must remove power (and ideally disconnect or isolate the part being measured).

Measuring resistance with a meter works by sending a small test current through the path and reading the resulting voltage. This only yields a true DC resistance when the circuit is passive, with no active power sources influencing it. If power is present, the circuit already has currents and voltages that interfere with the meter’s test signal, producing an inaccurate reading and potentially risking damage to the meter or components. So, to get a valid resistance measurement, you must remove power (and ideally disconnect or isolate the part being measured).