Which formula expresses power using voltage and resistance?

Which formula expresses power using voltage and resistance?

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

Answer: (D)

Power in a resistor can be written in several equivalent ways. When you know the voltage across the component and its resistance, the appropriate expression is P = V^2 / R. This comes from Ohm’s law V = IR and the power relation P = I^2 R. Substituting I = V/R into P = I^2 R gives P = (V/R)^2 × R = V^2 / R, which uses voltage and resistance directly. The form P = I^2 R uses current and resistance, and P = V I uses voltage and current; neither expresses power with both voltage and resistance. Since R × I would yield a voltage, not power, it doesn’t describe power.

Power in a resistor can be written in several equivalent ways. When you know the voltage across the component and its resistance, the appropriate expression is P = V^2 / R. This comes from Ohm’s law V = IR and the power relation P = I^2 R. Substituting I = V/R into P = I^2 R gives P = (V/R)^2 × R = V^2 / R, which uses voltage and resistance directly. The form P = I^2 R uses current and resistance, and P = V I uses voltage and current; neither expresses power with both voltage and resistance. Since R × I would yield a voltage, not power, it doesn’t describe power.