In the series circuit, what is the voltage across R1 if the current is 0.6 A and R1 = 4 Ω?

• A. 1.2 V
• B. 2.4 V
• C. 4.8 V
• D. 6.0 V

Answer: (B)

In a series circuit, the same current flows through every component, and the voltage drop across a resistor is found with Ohm’s law: V = I × R. With a current of 0.6 A through a resistor of 4 Ω, the voltage across that resistor is 0.6 × 4 = 2.4 V. So the voltage across R1 is 2.4 volts. The other values would require different currents: 1.2 V would need 0.3 A through 4 Ω, 4.8 V would need 1.2 A, and 6.0 V would need 1.5 A.