Which expression gives electrical power in terms of voltage and current?

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

Answer: (A)

Power is the rate at which energy is transferred in a circuit. When a component has a voltage V across it and current I flowing through it, the power it uses or delivers is simply P = V × I. This direct product comes from combining the idea of energy per charge (voltage) with charge flow per second (current).

The other forms, like P = I^2R or P = V^2/R, are valid ways to express power but they incorporate resistance instead of focusing on voltage and current directly. P = V / I would not give power in watts because dividing voltage by current yields a quantity with units of resistance, not power. For a quick check, if V is 120 V and I is 2 A, P = 120 × 2 = 240 W.