Practice question
Question
A steel plate has an area of 1.2m2 at 45∘C. What is the decrease in area when cooled to 5∘C? (αl\=1.2×10−5K−1)
Explanation
Given: A0 = 1.2m2, ΔT = 5−45 = −40∘C, αl = 1.2×10−5K−1. Area expansion: ΔA = A0×2αlΔT = 1.2×2×1.2×10−5×(−40). ΔA = 1.2×2.4×10−5×(−40) = −0.001152m2 (decrease of 0.001152m2). As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.001152 m². This satisfies dimensional consistency and physical conditions given, so option D is scientifically correct.