Answer: 32 W.
- A 32 W
- B 16 W
- C 64 W
- D 8 W
Correct answer: A. 32 W
Explanation: Q/t = kAΔT/L = 400 × 4×10<sup>-4</sup> × 100 / 0.5 = 32 W.
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.