Answer
Actual length is
23*10^-6 / C°
Work Step by Step
By using steel ruler we know that the mark is between 20.05 cm and 20.11cm
So,
ΔLs= Ls α ΔT
ΔLs=(20.11cm)(11 * 10^6 /C° )(270 °C - 20 C)
= 0.055cm
To find the actual length of rod
ΔL= (20.11 cm - 20.05) + 0.055cm = 0.115 cm
The coefficient of thermal expansion for the material of which the rod is made is then
α = ΔL / ΔT
= 0.115cm / 270 °C - 20°C
= 23 * 10^-6 / C°
