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Conduction
Beginner
Heat flow through a material by particle collisions.
Q/t = kAΔT/LHeat flows through a material from hot to cold by particle collisions and free electrons: Q/t = kAΔT/L. Metals have high k, gases low.
A 5 cm thick brick wall (k = 0.8) of 10 m² and 20 K difference: 3.2 kW.
Doubling thickness halves the rate.
In more detail
Conduction is heat transfer through a material by collisions of particles and movement of electrons, without bulk motion of the material. Metals conduct heat well, and gases conduct poorly.
Real-world uses
- Cooking pans are made of metal to conduct heat evenly.
- Insulating materials reduce heat loss through walls by poor conduction.
- A metal spoon in a hot drink becomes hot at the handle because heat flows through the metal by conduction.
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Frequently asked questions
Why does metal feel colder?
It conducts heat away from your hand quickly, even though it is at the same temperature as wood.
What affects the rate of conduction?
Thermal conductivity, area, temperature difference and thickness.
Why do metals feel colder than wood?
Metals conduct heat away from your hand quickly, while wood conducts it slowly, so the metal feels colder at the same temperature.
Related topics in Heat & Thermodynamics
Calorimetry · Phase diagrams · Triple and critical points · Thermal resistance · Convection · Radiation