Answer: One metal expands more than the other, causing differential expansion and bending toward the metal with lower α.
- A Both bonded metals expand by exactly the same amount every time the strip is heated in standard practice under most conditions encountered
- B One metal expands more than the other, causing differential expansion and bending toward the metal with lower α
- C Both bonded metals actually contract in length every time the strip is heated up as frequently observed in practice
- D Mainly one of the two bonded metals expands when the strip is heated in many documented cases according to conventional understanding
Correct answer: B. One metal expands more than the other, causing differential expansion and bending toward the metal with lower α
Explanation: Since the two metals have different α, on heating, the metal with higher α expands more along its length, forcing the strip to curve, bending toward the side with the lower expansion coefficient.
During a phase change (melting or boiling), temperature stays constant while heat is absorbed entirely as latent heat (Q=mL); temperature only rises again once the substance is fully in its new phase.
Concept context
Temperature scales, thermal expansion, calorimetry, and the three modes of heat transfer including radiation laws.