If the voltage in a circuit is kept constant and the resistance doubles, what happens to the current?

• A. It halves.
• B. It doubles.
• C. It stays the same.
• D. It quadruples.

Answer: (A)

When voltage is kept constant, current changes inversely with resistance according to Ohm’s law: I = V/R. If you double the resistance while keeping the voltage the same, the denominator doubles, so the current becomes half of what it was. For example, with a fixed voltage, doubling R cuts the current in half: I' = V/(2R) = (1/2)(V/R).

So the current halves because the same push (voltage) now has to push through a tougher path (double resistance). It won’t stay the same, it won’t double, and it won’t quadruple unless the resistance changes in those respective ways (which would require the voltage to change as well).