A 60 W light bulb is left on for 5.0 hours. How much electrical energy does it use, in kilowatt-hours?
Answer and explanation
Correct answer: A. 0.30 kWh
- Step 1: Power in kilowatts = 60 / 1000 = 0.060 kW. Step 2. Energy = 0.060 kW x 5.0 h = 0.30 kWh. Answer: 0.30 kWh. Why not the others: 3.0 kWh is ten times too large, 12 kWh divides the power by the time, and 300 is the energy in watt-hours, not kilowatt-hours.
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