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JAMB Physics 1990 Question 20

Question 20

Heat Transfer

Which of the following statements are correct? I. Land and sea breezes are natural convection currents. II. Convection may occur in liquids or gases but not in solids. III. The vacuum in a thermos flask prevents heat loss due to convection only.

  1. A.I and II only
  2. B.II and III only
  3. C.I and III only
  4. D.I, II and III.
Show the answer and explanation

Answer: A (I and II only)

Explanation

Breezes are convection currents, and convection needs a fluid. The vacuum stops conduction as well as convection, so III is wrong.