P2: ENERGY TRANSFER BY HEATING

Energy Transfer by Conduction

Metals are the best conductors of energy

Non-metal materials such as wool and fibreglass are the best insulators

The higher the thermal conductivity of a material, the higher the rate of energy transfer through it

The thicker a layer of insulating material, the lower the rate of energy transfer through it

Infrared Radiation

All objets emit and absorb infrared radiation

The hotter an object is, the more infrared insulation it emits in a given time

Blackbody radiation is radiation emitted by a body that absorbs all the radiation incident on it

The temperature of an object increases if it absorbs more radiation than it emits

The Earth's temperature depends on a lot of factors, including the absorption of infrared radiation from the Sun, and the emission of radiation from the Earth's surface and atmosphere

Specific Heat Capacity

The specific heat capacity of a substance is amount of energy needed to change the temperature of 1kg of the substance by 1°C

energy needed = mass x specific heat capacity x temperature change

The greater the mass of an object,the more slowly its temperature increases when it is heated

Heating and Insulating Buildings

Electric and/or gas heaters and gas or oil-fired central heating or solid-fuel stoves are used to heat houses

The rate of energy transfer from houses can be reduced by using:

loft insuation

cavity wall insulation

double-glazed windows

aluminium foil behind radiators

external walls with thicker bricks and lower thermal conductivity

Cavity wall insulation is insulation material that is used to fill the cavity between the two brick layers of an external house wall