Why Does a Bimetallic Strip Bend When Heated?

[Saladsamurai]

I have this multiple choice question:

Two thin strips of iron and zinc are riveted together to form a bimetallic strip that bends when heated. The iron is on the inside of the bend because:


(A) it has a higher coefficient of linear expansion
(B) it has a lower coefficient of linear expansion
(C)it has a lower specific heat
(D)it conducts heat better

Here is a poor "side-view" diagram of the scenario.
zinc--->((<----iron

I am going with B. Since the iron has a lower coeff. of linear expansion, it does not expand as 'willingly' as the zinc and thus 'holds' it down actually causing the bend rather than the zinc actually expanding.

This my reasoning. Am I correct in thinking this?

Casey

 

[rl.bhat]

Yes. You are right.

 

[ogb p]

Your reasoning is correct. The iron strip has a lower coefficient of linear expansion, meaning it expands less than the zinc strip when heated. This causes the iron strip to hold the zinc strip down, creating the bend in the bimetallic strip. This phenomenon is known as thermal expansion, where materials expand or contract when heated or cooled. In this case, the difference in coefficients of linear expansion between the two metals causes the bimetallic strip to bend. This is a common principle used in thermometers and thermostats.