Which heat loss mechanism occurs through contact with a solid surface?

• A. Radiation
• B. Conduction
• C. Convection
• D. Evaporation

Answer: (B)

Conduction is heat transfer by direct contact at the molecular level. When a solid surface touches a warmer or cooler body, energy is transferred through molecular interactions and free electrons from the hotter region toward the cooler region, moving heat across the interface. This requires physical contact, which is why heat loss through a solid surface occurs by conduction. Radiation, on the other hand, occurs without contact via electromagnetic waves; convection involves moving fluids; and evaporation is a surface phase change. The rate of conduction depends on the temperature difference, the contact area, the material’s thermal conductivity, and the quality of the interface.