When two metals are firmly joined and heated, they expand due to the heat. The expansion depends on their coefficients of thermal expansion. Here, metal A expands more than metal B on heating. This means that metal A has a higher coefficient of thermal expansion than metal B.
Option 1 depicts the original strip without any change. This can`t be the answer as we know both metals have expanded.
Option 2 shows bending towards the side of metal B. This is because metal A has expanded more, pushing the strip to bend in the direction of metal B, which has lesser expansion.
Option 3 and 4 show bending towards the side of metal A. This is incorrect as metal A has higher expansion and thus should push the strip towards metal B, not pull it towards itself.
Thus, the correct answer is Option 2 as it accurately illustrates the given situation on heating.