Thermal Physics

Thermal Physics

1. Thermal Conduction

   • Materials are made up of tiny moving particles
     • Higher temperature=faster particle movement
     • If one end of a metal bar is heated, the other end eventually gets hot too.
       • The heat is transferred as the faster particles pass on their extra motion to particles all along the bar.
         • this is called CONDUCTION
           • Metals are the best conductors.
           • Liquids and gases are poor conductors because they contain tiny pockets of trapped air.
         • More thermal energy is transferred if: the temperature difference across the end of the bars is increased, the cross section of the bar area is increased or if the length of the bar is reduced.
     • Atoms contain electrons. most are firmly attached but some are free to drift and when metal is heated, these free electrons speed up and move randomly.
       • As they move, they collide and vibrate. Thermal energy is transferred.
   • Some materials are better at conducting than others.
     • Poor conductors are called insulators.
     • Sometimes to tell if something is a good conductor or not , you can touch it.
       • When you touch metal, it feels cold because it is quickly conducting away your warmth.

2. Thermal Radiation

3. Thermal Convection

   • Liquids and gases are poor thermal conductors but if they are free to circulate then they can carry heat very quickly.