Which step is essential when preparing to measure resistance with an ohmmeter?

Which step is essential when preparing to measure resistance with an ohmmeter?

• A. Leave the circuit powered
• B. Connect in parallel
• C. Bring the circuit to high temperature
• D. Disconnect electrical power from the circuit

Answer: (D)

Measuring resistance requires the circuit to be de-energized. An ohmmeter injects a small test current to determine resistance, and any live power in the circuit can distort the reading or damage the meter. By disconnecting electrical power, you ensure the component is isolated, the measurement is accurate, and there’s no risk of shock or arcing. Leaving power on, wiring the meter in a way meant for other measurements, or heating the circuit are not appropriate steps and can lead to unsafe conditions or incorrect results.

Measuring resistance requires the circuit to be de-energized. An ohmmeter injects a small test current to determine resistance, and any live power in the circuit can distort the reading or damage the meter. By disconnecting electrical power, you ensure the component is isolated, the measurement is accurate, and there’s no risk of shock or arcing. Leaving power on, wiring the meter in a way meant for other measurements, or heating the circuit are not appropriate steps and can lead to unsafe conditions or incorrect results.