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Unilorin Post-UTME Physics 2022 (Model questions) Question 14

Question 14

Electrical Energy and Power

What is the cost of running seven 40W lamps and five 80W lamps for 12 hours if the electrical energy costs ₦7 per kWh?

  1. A.₦80.000
  2. B.₦45.36
  3. C.₦65.00
  4. D.₦57.12
Show the answer and explanation

Answer: D (₦57.12)

Explanation

Power = 7 × 40 + 5 × 80 = 680 W = 0.68 kW. Energy = 0.68 × 12 = 8.16 kWh. Cost = 8.16 × ₦7 = ₦57.12.