A steel wire of uniform area 2 mm2 is heated upto 50∘C and is stretched by tying its ends rigidly. The tension when the temperature falls from 50∘C and 30∘C is (Take Y = 2 × 1011 Nm−2 , α = 1.1 × 10−5∘C−1)
△ = αL(△T) = FA LY
∴ F = α(△T)AY
= 1.1 ×10−5×(50−30)×2×10−6×2×1011
= 88 N