What should be done before measuring resistance in a circuit?

Before measuring resistance in a circuit, it is essential to disconnect power to the circuit to prevent damage to the multimeter. Resistance measurements are typically conducted with the circuit powered down because measuring resistance involves passing a small current through the component or circuit being tested. If the circuit is live, applying this current can harm the multimeter and potentially lead to inaccurate readings.

When power is applied to the circuit, the multimeter may not only read a false value but could also experience internal damage due to the high voltage or current present. Therefore, ensuring that the circuit is completely de-energized is a critical step in safely and accurately measuring resistance. This practice is fundamental to electrical safety and reliable testing, allowing for proper troubleshooting and diagnostics without risking equipment failure.