P.2 - Energy Transfer by Heating

  • Conduction is the way in which energy is transferred (through heating by contact) from a hot body (or region) to a cooler one

  • The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material

  • Resolution is the smallest measurable increment of a device

  • Random errors cause readings to be spread about the true value, due to results varying in an unpredictable way

  • Systematic table errors cause readings to differ from the true value by a consistent amount each time a measurement is made

Infrared radiation

  • All bodies (objects), no matter the temperature, emit and absorb infrared radiation

  • The hotter the body, the more infrared radiation it radiates in a given time

  • A perfect black body, is an object that absorbs all radiation incident on it. A black body doesn’t reflect or transmit any radiation

  • The intensity and wavelength distribution of any emission depends on the temperature of the body

  • Intensity is the power transferred per unit area

  • No other object emits or absorbs electromagnetic radiation as effectively as a Black Body

  1. Infrared radiation from the sun is absorbed by the atmosphere and warms the ground

  2. The ground becomes warm and emits longer wavelength infrared radiation

  3. CO2 molecules absorb the infrared and re-emits it back to the ground

  4. The earth’s temperature rises

Specific Heat Capacity (S.H.C)

  • The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1kg of the substance by 1oc

  • Change in thermal energy = mass x S.H.C x temperature change / △E = mc△θ

  • θ = theta - use for temperature

  • △ = delta - use for change in energy