Power is the product of which two quantities?

• A. Resistance and Current
• B. Voltage and Current
• C. Voltage and Resistance
• D. Power and Voltage

Answer: (B)

Power is the rate at which electrical energy is transferred, and it’s found by multiplying the voltage across a component by the current flowing through it. This direct relationship is written as P = V × I, so power measured in watts comes from volts times amperes.

For example, if you have 12 volts across a device and 2 amperes flowing, the power is 24 watts.

Other pairings don’t define power in the general case. Multiply resistance by current and you get I × R, which isn’t power by itself (the power in a resistor is I^2R). Multiply voltage by resistance and you get V × R, which isn’t power unless you also apply Ohm’s law to relate V, I, and R. And multiplying power by voltage gives a different quantity (not power). The essential, widely used form for power is P = VI.