Physics GCSE OCR Gateway P1 - Energy For The Home

Heat and Temperature
1. Heat
  1. Measure of kinetic energy
  2. Absolute scale
    1. Can't go below 0
    2. Joules (J)
2. Temperature
  1. Measure of hotness
  2. Not absolute scale
    1. Celcius
    2. Farenheit
    3. Kelvin
    4. Can go below 0
3. Specific Heat Capacity (c)
  1. How much energy a material can store
  2. Energy = Mass x Specific Heat Capacity x Temperature Change
    1. E = m x c x △t
  3. J/kg/°C
  4. Water has c of 4200 J/kg/°C
Melting and boiling
1. Energy is needed to break intermolecular bonds
2. Flat spots on heating graphs = melting/boiling/condensing/freezing point
3. Specific Latent Heat
  1. Energy needed to change state
  2. J/kg
  3. Energy = Mass x Specific Latent Heat
    1. E = m x slh
Conduction, Convection + Radiation
1. Conduction
  1. Occurs mainly in solids
  2. Vibrating particles hit other particles
    1. Kinetic energy passed on to neighboring particles
2. Convection
  1. Occurs mainly in liquids and gases
  2. Particles heat up, move faster, become less dense
    1. Heated particles rise, cooler ones take its place + heat up
      1. Convection currents form
3. Radiation
  1. Infrared
  2. Needs no medium to travel through
    1. Can travel through vacuums e.g. Space
  3. Can only occur through transparent substances
  4. Amount of radiation emitted/absorbed depends on colour and texture
    1. Matt Black surfaces absorb and emit well
      1. Reflect poorly however
    2. Shiny surfaces absorb and emit poorly
      1. Reflect well however
Saving Energy
1. Home insulation methods
  1. Loft insulation
    1. Fibreglass 'wool' laid across loft floor
    2. Reduces conduction from ceiling to roof space
  2. Hot water tank jacket
    1. Reduces conduction
  3. Double glazing
    1. Two layers of glass with air gap between
    2. Reduces conduction
  4. Thick curtains
    1. Reduces conduction and radiation through window
  5. Draught-proofing
    1. Foam and plastic strips around doors and windows
    2. Reduces convectinon
  6. Cavity walls and Insulation
    1. Two layers of bricks with air gap between
      1. Insulating foam in air gap
    2. Reduces conduction and convection
2. Efficiency
  1. The less energy wasted, the more efficient a device is
  2. Efficiency (%) = Useful Energy Output / Total Energy Input x 100
Waves
1. Have Amplitude, Wavelength and Frequency
  1. Amplitude - Displacement from rest position
  2. Wavelength - Length of one full cycle
  3. Frequency - Number of cycles per second
2. Wave speed = Frequency x Wavelength
3. Properties
  1. Can be reflected, refracted or diffracted
    1. Reflection of light is why we can see things
      1. Angle of incidence = Angle of relfection
    2. Diffraction - Waves spread out when passing through a gap or pass an object
      1. Maximum diffraction when gap is same width as wavelength
    3. Refraction - Change in wave speed, which can cause a change in direction
      1. Waves travel slower in denser mediums
        If wave enters denser medium at an angle, part of wave slows down before another part, causing it to change direction
4. EM Waves
  1. Radio
  2. Micro
  3. Infra-red
  4. Visible Light
  5. Ultra-Violet
  6. X-Ray
  7. Gamma Ray
  8. Properties depend on frequency and wavelength
    1. Higher frequency = more dangerous to living cells
    2. Waves at end of spectrum pass through stuff
    3. Waves in middle of spectrum get absorbed by stuff

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Physics GCSE OCR Gateway P1 - Energy For The Home

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