WAEC Physics 2017 Objective — Question 21
Question 21 of 50 from the West African Examinations Council (WAEC) Physics 2017 Objective paper, with the correct answer and a full explanation.
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An electric drill rated 400W is used to drill a hole in copper of mass 400 g in 20 s. Calculate the rise in temperature if all the heat produced is absorbed by the copper. [Specific heat capacity of copper = 400 J kg⁻¹ K⁻¹]
- A. A. 100°C
- B. B. 75°C
- C. C. 50°CCorrect
- D. D. 45°C
Explanation
Power = 400W, mass of copper = 400g = 0.4kg, time = 20s, rise in temperature = ? Heat absorbed by copper = power x time = 400x20 = 8000J. Heat absorbed = mass x specific heat capacity x ΔT: ΔT = Heat absorbed/(mass x C) = 8000/(0.4x400) = 50°C.
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