In the motor example, a 12-volt supply delivering 10 amperes results in how much power drawn from the supply?

• A. 120 W
• B. 24 W
• C. 1.2 W
• D. 0.12 W

Answer: (A)

Electrical power from a DC supply is found by multiplying voltage by current. Using P = V × I, 12 volts times 10 amperes equals 120 watts. So the power drawn from the supply is 120 W. In a motor, that electrical power splits into mechanical work and losses as heat, but the input power from the supply remains 120 W. The other numbers would require different currents (for example, 12 V × 2 A = 24 W, 12 V × 0.1 A = 1.2 W, or 12 V × 0.01 A = 0.12 W).