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 :
Know your College Admission Chances Based on your Rank/Percentile, Category and Home State.
Get your JEE Main Personalised Report with Top Predicted Colleges in JoSA
A bimetallic strip bends due to differential thermal expansion. The coefficient of linear expansion (α) determines how much a material expands per degree temperature change. Iron has a lower α than zinc. When heated, zinc expands more than iron, forcing the strip to bend with the less expanding iron on the inside of the curve.
Mathematically, the change in length is ΔL = L0αΔT. For the same ΔT, a smaller α means less ΔL.
Final answer: it has a lower coefficient of linear expansion