Which formula correctly represents power in terms of voltage and current?

• A. P = V / I
• B. P = I / V
• C. P = V × I
• D. P = V × I^2

Answer: (C)

Power is the rate at which energy is delivered to a load. That rate comes from how much energy per unit charge there is (voltage) and how much charge is moving per unit time (current). So the instantaneous power is the product of voltage and current: P = V × I. This directly links how strong the driving force is (voltage) with how much charge is flowing (current) to determine how fast energy is being delivered.

In a resistor, you can also derive other common forms: using Ohm’s law V = I R, you get P = I^2 R or P = V^2 / R. The other expressions don’t represent power on their own—V/I equals resistance, and I/V is the reciprocal of resistance—so they’re not the correct way to calculate power in general.