# Heat on rod!

Two straight metallic strips each of thickness $$t$$ and length $$l$$ are riveted together. Their coefficients of linear expansion are $$\alpha_1$$ and $$\alpha_2$$. If they are heated through a temperature $$\Delta t$$, the bimetallic strip will bend to form an arc of radius $$r$$, find $$r$$.

(a) $$\dfrac t{(\alpha_1 + \alpha_2) \Delta t}$$.
(b) $$\dfrac t{(\alpha_2-\alpha_1) \Delta t}$$.
(c) $${(\alpha_1+\alpha_2) \Delta t}$$.
(d) $${(\alpha_2-\alpha_1) \Delta t}$$.

Type 1 for option (a),
Type 2 for option (b),
Type 3 for option (c),
Type 4 for option (d).

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