A metre scale made of steel reads accurately at 20∘C. In a sensitive experiment, distances accurate up to 0.055 mm in 1 m are required. Find the range of temperature in which the experiment can be performed with this metre scale. Coefficient of linear expansion of steel =11×10−6 ∘C−1
T1=20∘ C
ΔL = 0.055 mm
=0.055×10−3m
T2=?
αst=11×10−6/∘C
we know ΔL=L0 αΔT
⇒ 0.055×10−3=1×11×10−6×T1±T2)
⇒ 5×10−3=(20±T2)×10−3
⇒ 20±T2=5
⇒ T2=20+5=25∘C
or 20 - 5 = 15∘
Hence the experiment can be performed from 15∘ to 25∘ C