L6 - Thermal Conduction

objectives

Conduction

• All materials are made up of tiny, moving particles (atoms or molecules).
• The higher the temperature, the faster the particles move.
• If one end of a metal bat is heated as above, the other end eventually becomes too hot to touch.
• Thermal energy (heat) is transferred from the hot end to the cold end as the faster particles pass on their extra motion to particles all along the bar.
• The process is called conduction.
• More thermal energy is transferred every second if:
  • the temperature difference across the ends of the bar is increased
  • the cross-sectional (‘end-on’) area of the bar is increased
  • the length of the bar is reduced.

Thermal Conductors and Insulators

A video on conductors and insulators

Using Thermal Insulators

• In countries where buildings need to be heated, good insulation means lower fuel bills.
• Above are some of the ways in which insulating materials are used to reduce heat losses from a house:

1. Plastic foam lagging round the hot water storage tank.
2. Glass or mineral wool insulation in the loft.
3. Wall cavity filled with plastic foam, beads, or mineral wool.
4. Double-glazed windows: two sheets of glass with air between them.

How Materials Conduct

Metal Electrons under a Microscope