Heat Transfer

Conduction passes heat through a solid: the hot end's atoms vibrate harder and jostle their neighbours, so energy travels along without the material moving. Good conductors (metals) carry it fast; insulators resist it. Convection works in fluids: heated fluid expands, becomes less dense and rises, cooler fluid sinks to replace it, setting up a circulating current that carries heat bodily. Radiation is infrared energy emitted by any warm surface — it needs no medium at all (it crosses a vacuum, which is how the Sun warms us), and a hot object radiates much more (rate ∝ T⁴, so dark, hot surfaces glow).

• Try this: In conduction, drop the conductivity toward an insulator and watch the heat crawl.
• Try this: In convection, watch the current — hot fluid up one side, cool fluid down the other.
• Try this: In radiation, raise the temperature and see the emission jump (it grows as T⁴).
• Try this: Note radiation still works with a gap — no material is needed to carry it.