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A bimetallic strip is made from two identical strips of copper and brass with linear expansion coefficients alpha_c and alpha_b. On heating by delta_T it bends into an arc of radius of curvature R. How does R depend on the parameters?

1. proportional at delta_T
2. inversely proportional to delta_T
3. proportional to |alpha_b - alpha_c|
4. inversely proportional to |alpha_b - alpha_c|

Correct answer: inversely proportional to delta_T

Solution

Since R = t / [(alpha_b - alpha_c) delta_T], R is inversely proportional to delta_T (and also inversely proportional to |alpha_b - alpha_c|).

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