Which heat transfer mechanism occurs through direct contact between objects?

Which heat transfer mechanism occurs through direct contact between objects?

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

Answer: (A)

Direct contact transfers heat by conduction: energy moves through interactions at the boundary, as molecules in the hotter object collide with cooler ones and share their kinetic energy. In solids, this happens via vibrations of the lattice and, especially in metals, by free electrons that quickly carry energy from the hot region to the cooler region across the contact. Conduction requires physical touch, unlike the other methods. Convection needs moving fluid to transfer heat by bulk motion. Radiation can transfer heat through electromagnetic waves without touching. Evaporation involves a liquid changing to vapor at a surface and is a latent heat process, not the primary way heat moves between two touching bodies. So the mechanism through direct contact is conduction.

Direct contact transfers heat by conduction: energy moves through interactions at the boundary, as molecules in the hotter object collide with cooler ones and share their kinetic energy. In solids, this happens via vibrations of the lattice and, especially in metals, by free electrons that quickly carry energy from the hot region to the cooler region across the contact. Conduction requires physical touch, unlike the other methods. Convection needs moving fluid to transfer heat by bulk motion. Radiation can transfer heat through electromagnetic waves without touching. Evaporation involves a liquid changing to vapor at a surface and is a latent heat process, not the primary way heat moves between two touching bodies. So the mechanism through direct contact is conduction.