WAEC Physics 2013 Objective — Question 22
Question 22 of 50 from the West African Examinations Council (WAEC) Physics 2013 Objective paper, with the correct answer and a full explanation.
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An electric heater has a resistance of 50Ω. When it is immersed in water and connected to mains source, it draws a current of 4.0A. Calculate the heat gained by the water if the heater is switched on for 2 minutes, assuming no heat losses to the surroundings.
- A. 400 J
- B. 1600 J
- C. 24000 J
- D. 96000 JCorrect
Explanation
Power = I²R = 4²×50 = 800W. Time = 2×60 = 120s. Heat gained = Power×time = 800×120 = 96000J.
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