Physics
Physics
Problem
A bimetallic strip is made by firmly bonding brass and steel strips of equal length. The coefficient of linear expansion of brass is greater than that of steel. When the strip is uniformly heated, it will bend a) twist about its length rather than bend b) towards the brass side c) towards the steel side d) remain perfectly straightIntuitive explanation
When two materials with different expansion rates are locked together, they can't expand independently—so one must bend to accommodate the mismatch. Since brass expands more than steel when heated, it "wants" to get longer, but the steel holds it back. The strip curves with brass on the outside of the bend, because the outer edge of a curve is longer than the inner edge. This is the key insight: unequal thermal expansion forces geometric bending.
Intuitive explanation
When two materials with different expansion rates are locked together, they can't expand independently—so one must bend to accommodate the mismatch. Since brass expands more than steel when heated, it "wants" to get longer, but the steel holds it back. The strip curves with brass on the outside of the bend, because the outer edge of a curve is longer than the inner edge. This is the key insight: unequal thermal expansion forces geometric bending.