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JAMB Physics 1994 Question 27

Question 27

Heat Transfer

Two similar kettles containing equal masses of boiling water are placed on a table. If the surface of one is highly polished and the surface of the other is covered with soot, which of the following observations is correct?

  1. A.The two kettles will cool down at the same rate
  2. B.The polished kettle cools down more quickly by conduction
  3. C.The kettle covered with soot cools down more quickly because it is a good radiator of heat
  4. D.The kettle covered with soot cools down more quickly by the process of heat convection.
Show the answer and explanation

Answer: C (The kettle covered with soot cools down more quickly because it is a good radiator of heat)

Explanation

Dull black surfaces are good radiators of heat; shiny polished surfaces are poor radiators, so the sooty kettle loses heat faster.