Heat transfer

  Heat flows when there is a difference in temperature between two places. It will flow from the hotter to the cooler place. There are three methods by which it can do this. These are conduction, convection and radiation.

CONDUCTION

This is the transfer of heat energy through a substance from a hotter part to a cooler part without any movement of substance itself.

Heat is being transferred along this road by conduction.

Particles at the hot end vibrate and move around more vigorously.

This additional motion is passed on to neighboring particles causing them to move more vigorously.

As a result the cold end of the rod gradually becomes warmer.

All metals are good conductors of heat.

  Most non-metals are poor conductors of heat.

Most liquids are poor conductors.

Gases (air) are excellent insulators.

They do no allow heat to pass though them easily by conduction.

Woven materials, e.g. wool and cotton, contain trapped air and are excellent insulators.