What might happen if you attempt to measure resistance while the circuit is powered?

When attempting to measure resistance in a powered circuit, there are several important reasons why this is problematic. First, a multimeter set to the resistance measurement mode applies a small voltage to the circuit to determine resistance. If the circuit is powered, this additional voltage can interfere with the reading, resulting in inaccurate measurements. Consequently, the meter may show values that do not reflect the true resistance because the powered components can alter the flow and measurement of current.

Additionally, there is a risk of damaging the multimeter. Many multimeters are designed to measure resistance only in de-energized circuits. If voltage from the powered circuit exceeds the multimeter’s voltage rating, it could lead to internal damage or even cause the meter to fail completely. This combination of potential inaccuracies in the readings and the risk to the multimeter itself is why both concerns are valid, affirming that attempting to measure resistance in a powered circuit is unsafe and should be avoided.