A manganese sheet of dimensions 20cm×30cm at 25∘C is heated to 75∘C, if the area of the sheet is increased by 0.72cm2, what is the coefficient of superficial thermal expansion of manganese in 10−6∘C−1?
24
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Solution
The correct option is A 24 Given: The initial dimensions of the manganese sheet, 20cm×30cm⟹ Initial area, A0=20×30=600cm2 Increase in the area, ΔA=0.72cm2 The rise in temperature, ΔT=75−25=50∘C We know that the coefficient of superficial thermal expansion, β is given by: β=ΔAA0ΔT