A metal rod has a length of 1m at 300C ,  'α' of metal is  2.5×10−5/0C, the temperature at which it will be shortened by 1mm is

coefficient of linear expansion of solid isα=ΔllΔthere Δl =-1mm=-10-3m=decrease in lengthl is initial length=1m; Δt is change in temperature;initial temperature = 300C; α=2.5x10-5/C  0     substitute given values in above equation2.5×10−5=−10−31×t2−30t2−30=−12.5×10−2=−1002.5t2−30=−40t2=−40+30=−100C=temperature at which rod will be shortened