If voltage doubles while resistance remains the same, what happens to current?

• A. Current stays the same
• B. Current decreases
• C. Current doubles
• D. Current goes to zero

Answer: (C)

Ohm's law shows that current is proportional to voltage when the resistance is fixed: I = V / R. If the resistance doesn’t change and you double the voltage, the current must double as well, because you’re dividing the doubled voltage by the same resistance. For example, with R = 10 ohms, a voltage of 5 V gives I = 0.5 A; increasing V to 10 V gives I = 1 A. Since current scales directly with voltage at a constant resistance, doubling the voltage doubles the current. The other possibilities would require changing the resistance or removing the voltage, which isn’t indicated here.