OCFA Securing Utilities Practice Test

Which formula expresses the relationship between Watts, Volts, and Amps?

Watts = Volts × Amps Watts = Volts + Amps Watts = Amps ÷ Volts Watts = Volts − Amps

Correct Answer:

Watts = Volts × Amps

Explanation:

Power in an electrical circuit is defined as the rate at which energy is transferred, and in simple circuits it equals the product of the voltage across the circuit and the current flowing through it. Therefore, Watts come from multiplying Volts by Amps, expressed as P = V × I. The units line up: volt × ampere yields watt. This is why the expression that uses multiplication is correct. Addition, subtraction, or division do not yield power in watts. For example, at 120 volts and 2 amps, power is 240 watts. In AC circuits with a nonzero power factor you’d have P = VI cos φ, but for basic problems with resistive loads, P = V × I works.

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