To accurately measure the resistance of a resistor within a circuit, what must you do first?

To accurately measure the resistance of a resistor within a circuit, it is crucial first to ensure that you do not have the resistor connected in a live circuit. This is because measuring resistance requires the resistor to be isolated from any power source or parallel pathways that could affect the reading. By disconnecting one end of the resistor, you effectively eliminate any influence from other components in the circuit and ensure that the measurement reflects the true resistance of the resistor itself.

Disconnecting one end allows the use of a multimeter or ohmmeter to measure the resistance without interference from voltage or current present in the circuit, leading to accurate measurements. This action also protects the multimeter from potential damage caused by applying voltage to it during a resistance measurement.

Thus, this step is essential for obtaining a correct and reliable reading of the resistor's resistance value.