Savchenko Problem 8.3.12

The key insight is that you don't need to isolate the resistor—you can use Ohm's law directly on the intact circuit. By measuring the voltage across $R$ with a voltmeter and the current through it with an ammeter, you can calculate $R = V/I$ without disconnecting anything. The trick is placing the ammeter in series with $R$ (so current flows through it) and the voltmeter in parallel across $R$ (so it reads the potential difference), then letting the battery drive the circuit and taking your readings.

The key insight is that you don't need to isolate the resistor—you can use Ohm's law directly on the intact circuit. By measuring the voltage across $R$ with a voltmeter and the current through it with an ammeter, you can calculate $R = V/I$ without disconnecting anything. The trick is placing the ammeter in series with $R$ (so current flows through it) and the voltmeter in parallel across $R$ (so it reads the potential difference), then letting the battery drive the circuit and taking your readings.