Which pair of units correctly relates electrical quantities: voltage and current?

Which pair of units correctly relates electrical quantities: voltage and current?

• A. volt / amp
• B. watt / volt
• C. watt / amp
• D. volt / watt

Answer: (A)

This item is testing how voltage and current relate through Ohm’s law. Ohm’s law says V = I R, so if we solve for resistance, R = V / I. That means the ratio of voltage to current carries the unit of resistance, which is the ohm. Since 1 ohm equals 1 volt per ampere, expressing the relationship as volts per amp captures how voltage and current connect for a given resistance. In other words, volt per amp is the natural way to relate voltage and current because it directly encodes the resistance between them. (Power relations like P = VI link voltage and current through power, but they don’t describe the direct voltage–to–current relationship the way V/I does.)

This item is testing how voltage and current relate through Ohm’s law. Ohm’s law says V = I R, so if we solve for resistance, R = V / I. That means the ratio of voltage to current carries the unit of resistance, which is the ohm. Since 1 ohm equals 1 volt per ampere, expressing the relationship as volts per amp captures how voltage and current connect for a given resistance. In other words, volt per amp is the natural way to relate voltage and current because it directly encodes the resistance between them. (Power relations like P = VI link voltage and current through power, but they don’t describe the direct voltage–to–current relationship the way V/I does.)