Which pair is directly proportional according to Ohm's Law?

Which pair is directly proportional according to Ohm's Law?

• A. Voltage and current
• B. Current and resistance
• C. Voltage and resistance
• D. Voltage and power

Answer: (A)

In Ohm’s Law, current changes in direct proportion to voltage when the resistance stays the same. Since V = I × R, solving for current gives I = V / R. If you hold R constant and double the voltage, the current doubles as well—clear direct proportionality. For example, with a constant resistance of 5 Ω, increasing voltage from 10 V to 20 V makes current go from 2 A to 4 A. That same proportional change wouldn’t hold for current and resistance (they are inversely related when voltage is fixed), and voltage and resistance don’t show a simple direct proportionality in general because both can change together depending on the circuit. Power also isn’t directly proportional to voltage alone; P = V × I = V^2 / R, which means changing voltage changes power in a quadratic way when resistance is fixed.

In Ohm’s Law, current changes in direct proportion to voltage when the resistance stays the same. Since V = I × R, solving for current gives I = V / R. If you hold R constant and double the voltage, the current doubles as well—clear direct proportionality.

For example, with a constant resistance of 5 Ω, increasing voltage from 10 V to 20 V makes current go from 2 A to 4 A. That same proportional change wouldn’t hold for current and resistance (they are inversely related when voltage is fixed), and voltage and resistance don’t show a simple direct proportionality in general because both can change together depending on the circuit. Power also isn’t directly proportional to voltage alone; P = V × I = V^2 / R, which means changing voltage changes power in a quadratic way when resistance is fixed.