Which term describes heat transfer by direct contact between objects of different temperatures?

Which term describes heat transfer by direct contact between objects of different temperatures?

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

Answer: (A)

Conduction is heat transfer by direct contact between objects of different temperatures. When two surfaces touch, energy flows from the hotter one to the cooler one through molecular interactions—vibrating lattice atoms pass energy to neighboring atoms, and in metals free electrons move energy rapidly across the interface. This process continues until temperatures equalize. Radiation, in contrast, transfers heat via electromagnetic waves and can occur without contact; evaporation involves a liquid changing to vapor at the surface and is a phase-change mechanism; convection requires movement of a fluid to carry heat.

Conduction is heat transfer by direct contact between objects of different temperatures. When two surfaces touch, energy flows from the hotter one to the cooler one through molecular interactions—vibrating lattice atoms pass energy to neighboring atoms, and in metals free electrons move energy rapidly across the interface. This process continues until temperatures equalize. Radiation, in contrast, transfers heat via electromagnetic waves and can occur without contact; evaporation involves a liquid changing to vapor at the surface and is a phase-change mechanism; convection requires movement of a fluid to carry heat.