Know that many solids conduct thermal energy better than thermal insulators but do so less well than good thermal conductors.
Conduction is the transfer of heat through a material without any bulk motion of the material itself. Think of it like a line of people passing a hot potato from one hand to the next.
Good conductors (like copper, aluminium) have many free electrons that help transfer energy. Insulators (like wood, plastic) have tightly bound electrons, so heat moves slowly.
| Material | Thermal Conductivity (\$k\$) | Example Use |
|---|---|---|
| Copper | ~401 W m⁻¹ K⁻¹ | Heat sinks, cooking pans |
| Aluminium | ~237 W m⁻¹ K⁻¹ | Air‑conditioning ducts, car radiators |
| Wood | ~0.12 W m⁻¹ K⁻¹ | Building insulation, wooden furniture |
| Plastic | ~0.2 W m⁻¹ K⁻¹ | Thermal gloves, kitchen utensils |
Heat transferred by conduction:
\$Q = k A \dfrac{\Delta T}{L}\$
\$Q\$ = heat transferred (J), \$k\$ = thermal conductivity (W m⁻¹ K⁻¹), \$A\$ = cross‑sectional area (m²), \$\Delta T\$ = temperature difference (K), \$L\$ = length (m).
Imagine a train of people (atoms) passing a hot ball (thermal energy). In a conductor, the train is long and the people are close together, so the ball moves quickly. In an insulator, the train is short and people are spaced apart, so the ball takes longer to reach the end.