An aluminum measuring rod, which is correct at 5oC measures the length of a line as 80 cm at 45oC.If thermal coefficient of linear expansion of aluminum is 2.50×10−5/∘C,  the correct length of the line is:

The 80 cm mark on the aluminum rod is really at a greater distance from the zero position than indicated because of the increase in temperatureΔθ=40∘C. The increased length isΔL=αA1LA1Δθa=2.50×10−5(80)(40)=0.08cmThe correct length of the line isL=80+0.08=80.08cm