Question

A unit scale is to be prepared whose length does not change with temperature and remains 20 cm, using a bimetallic strip made of brass and iron each of different length. The length of both components would change in such a way that difference between their lengths remains constant. If length of brass is 40 cm and length of iron will be ___ cm.

Answer 1

ℓB1+αBΔT−ℓi1+αiΔT=ℓB−ℓi
αBℓB=ℓiαi 1.8×10−5×40=ℓi×1.2×10−5
ℓi=$\frac{1.8×10^{−5}×40}{1.2×10^{−5}}$=$\frac{3×40}{2}$=60
ℓi=60cm