Conduction

Conduction: heat transfer through a material WITHOUT bulk motion of matter — vibrating molecules and electrons share energy.

Dominant mechanism in solids, especially metals (free electrons).

Fourier's law: heat current dQ/dt = −kA·(dT/dx), where k = thermal conductivity (W/m·K).

Steady-state through a slab: dQ/dt = kA·ΔT/L, where L is thickness.

Good conductors: metals (Cu: ~400 W/m·K, Ag: ~430, Al: ~240). Poor conductors (insulators): wood, plastic, air.

Thermal resistance R = L/(kA) — analogous to electrical resistance. Series and parallel rules apply.

Free electrons in metals carry heat efficiently (Wiedemann-Franz law: k/σ ∝ T).

Used in: heat sinks, thermos flasks (insulation), thermal grease (improve conduction).