Question

Two identical rectangular strips, one of copper and the other of steel, are riveted to form a bi-metal strip. On heating, the bi-metal strip will

• A. Bend
• B. Twist
• C. Elongate
• D. Shorten

Answer 1

The correct option is A

Bend

Thermal expansion

1. Thermal expansion is the process of increasing in length of an object due to the effect of heating or an increase in temperature.
2. The expansion of an object depends upon the shape of the object, change in temperature, and the coefficient of thermal expansion of the material.
3. Since the copper and steel strips are identical, and both are riveted together, the expansion will not depend upon the shape.
4. Again, the change in temperature for both strips is equal, as the strips are combined together to form one bi-metal strip.
5. The coefficient of friction for the materials is different, which will determine which metal will expand more.

Since the material having the larger value of the coefficient of friction will expand more, one side of the bi-metal strip will tend to bend.

Hence, option (A) is correct.