P1__Energy

Thermal Conductivity

The thermal conductivity of a material tells you how quickly energy is transmitted through thermal conduction. You can test this by having materials of the same diameter and length and covering the end in wax and seeing how fast the wax melts

Insulating Buildings

Factors that affect rate of heat loss include:

  • Thickness of walls and roof
  • Thermal conductivity of walls and roof

You can reduce the thermal conductivity by using thermal insulators which have low thermal conductivity as there could be:

  • Gaps of air which has low thermal conductivity
  • Reflect infrared radiation

Infrared Radiation

Infrared Radiation (IFR) is part of the EM spectrum. All objects emit and absorb IFR. The higher the temperature the more IFR an object emits in a given time.

If an objects temperature is constant then:

  • IFR emitted = IFR absorbed
  • IFR is emitted across a continuous range of wavelengths

An objects Temperature will increase if it absorbs IFR at a higher rate then it emits it. If it is cold it absorbs at a lower rate then it emits.

Black Body

A theoretical object that absorbs 100% of IFR that falls on it

Radiation and Earth’s Temperature

  • The sun emits lots of radiation which heats Earth’s surface
  • Some is reflected by the earths surface
  • Some of this then goes back into space
  • However some of it is absorbed by greenhouse gases in the atmosphere which then re-emit IFR increasing Earth’s Temperature