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JAMB Physics 1985 Question 18

Question 18

Thermal Expansion

A thin aluminium plate has a surface area of 1.500 m2 at 20°C. What will be its surface area when it is cooled to −20°C? (Take the linear expansivity of aluminium to be 2.5 × 10−5 K−1).

  1. A.1.503 m2
  2. B.1.500 m2
  3. C.1.498 m2
  4. D.1.497 m2
  5. E.1.490 m2.
Show the answer and explanation

Answer: D (1.497 m2)

Explanation

Area expansivity = 2 × 2.5 × 10−5 = 5 × 10−5 K−1. Change = 1.5 × 5 × 10−5 × (−40) = −0.003 m2, giving 1.497 m2.