What is the only heat transfer mode that (normally) works in a solid?

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

Answer: (C)

Conduction is the process by which heat energy is transferred through a solid by direct contact between particles. In a solid, particles are fixed in place and can’t flow like a liquid, so convection can’t occur. Energy moves from hotter regions to cooler ones through neighboring particles colliding and transferring vibrational energy, and in metals, free electrons quickly carry energy from hot to cold regions across the lattice. Radiation can transfer heat through space and can involve solids, but when we consider heat moving inside a solid, conduction is the dominant mechanism. Evaporation is a phase change from liquid to vapor and isn’t a mode of heat transfer within a solid.