Physics Unit 1 Heat transfer

• Occurs mainly in SOLIDS
• METALS are the best conductors due to their free electrons and close particle arrangement
• Poor conductors are known as insulators

How conduction works: one end of a solid is heated the particles at that end gain kinetic energy and vibrate more violently. This energy gets passed on to the neighboring particles and thus through the solid.

In metals this process is faster as their free electrons gain kinetic energy and move through the transferring their energy by colliding with other particles.

• Occurs in fluids (gasses and liquids)

How convection works: when a fluid is heated it expands. it becomes less dense and rises causing circulation as the warm fluid is replaces by cooler, denser fluid. As it rises it cools down resulting in an increase of density causing the fluid to fall. 

• energy transfer by electromagnetic waves (infra-red)
• doesnt involve particles, only waves
• all objects emit thermal radition
•  DARK SURFACES = absorbe more, emit more
• LIGHT URFACES = reflect more, emit less