Final Answer:
When a compound strip of iron and brass is heated, it experiences differential expansion due to the distinct coefficients of thermal expansion of iron and brass. The iron expands less than brass, causing the strip to curve, with the brass on the convex side.
Explanation:
When the compound strip of iron and brass is heated, the metals expand due to the increase in temperature. However, iron and brass have different coefficients of thermal expansion. Iron typically has a lower coefficient than brass. As a result, when heated, the brass expands more than the iron. This discrepancy in expansion rates causes the strip to bend. The brass, expanding more, pushes against the less expanded iron, leading to the strip curving with the brass on the convex side and the iron on the concave side.
The formula for thermal expansion is ΔL = αLΔT, where ΔL is the change in length, α is the coefficient of thermal expansion, L is the original length, and ΔT is the change in temperature. Given the different coefficients of expansion for iron and brass, when the strip is heated, the unequal expansions result in a bending effect. This phenomenon is utilized in devices like thermostats and bimetallic strips, where differential expansion due to temperature changes is harnessed to activate switches or mechanisms.
In summary, the differential expansion of iron and brass due to their distinct coefficients of thermal expansion causes the compound strip to bend when heated. This behavior is a fundamental principle in various engineering applications, especially in designing devices sensitive to temperature changes.