First slide
Thermal expansion
Question

Two thin metal strips, one of brass and the other of iron are fastened together parallel to each other. Thickness of each strip is 1 mm. If the strips are of equal length at 0°C . The inner radius of the arc formed by the bimetallic strip when heated to 80°C is (Coefficient of linear expansion of brass = 19×10–6/0C & of iron = 12 × 10–6/0C).

Easy
Solution

d = t1 + t2 = 1 + 1 = 2mm = 2 x 10-3m
θ1 = 00C, θ2 = 800C, α1 = 19 x 10-6, α2 = 12 x 10-6
Inner  radius of curvature of bimetallic strip
\large r=\frac {d}{\left (\alpha_1-\alpha_2 \right )\Delta \theta }=\frac {2\times 10^{-3}}{(19-12)\times 10^{-6}(80-0)}=3.57m
 

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