The ohmmeter must be connected to a circuit when the circuit power is turned on.

The ohmmeter must be connected to a circuit when the circuit power is turned on.

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

Answer: (B)

Measuring resistance with an ohmmeter relies on injecting a small known current into the component and reading the resulting voltage drop. If the circuit is powered, other sources drive current and voltage through the path, making the reading unreliable or invalid. The power in the circuit can also feed back into the meter, potentially damaging the ohmmeter or fuses in the power source. For accurate and safe results, turn off the power and discharge any capacitors before connecting the ohmmeter across the component you’re testing.

Measuring resistance with an ohmmeter relies on injecting a small known current into the component and reading the resulting voltage drop. If the circuit is powered, other sources drive current and voltage through the path, making the reading unreliable or invalid. The power in the circuit can also feed back into the meter, potentially damaging the ohmmeter or fuses in the power source. For accurate and safe results, turn off the power and discharge any capacitors before connecting the ohmmeter across the component you’re testing.