A series circuit consists of a variable power source, a resistor of known resistance, and a resistor of unknown resistance. The voltage of the power supply is varied, and the potential difference across the unknown resistor and the current through the circuit are measured by a voltmeter and an ammeter, respectively. Which of the following graphs indicates a constant resistance for the unknown resistor and provides the best value for the resistance R? 10 Current (Amp) 0.52 15 10 Voltage (V) 10 Current (Amp) 1.52 15 10 Voltage (V) 20 Current (Amp) 10- 1.5 32 od 5 10 15 Voltage (V) 10- Current (Amp) 0.5 22 10 15 5 Voltage (V) Voltage (V) 10- Current (Amp) 1.5 12 E 0 0 5 10 15 Voltage )
