Physics P1 Revision

Energy
1. Heat
  1. Can be transferred by conduction, convection, or radiation
  2. Infrared radiation
    1. Electromagnetic waves
    2. Dark matt surfaces absorb and emit information best
    3. Shiny silver surfaces best reflect heat
  3. All objects absorb and emit radiation
  4. Rate of heat transfer depends on surface area
  5. Specific heat capacity
    1. Energy (E in Joules)= Mass (M in kg) x Specific Heat Capacity (J/kgC) x Temperature change (theta)
2. Types of energy
  1. Electrical Light Sound Kinetic Nuclear Thermal Gravitational Elastic Chemical
    1. The last three are forms of stored energy
3. Conduction, Convection and Radiation
  1. Conduction
    1. Kinetic theory explains the 3 states of matter (solid, liquid, gas)
      1. Solid- strong forces of attraction, not much energy so can only vibrate around fixed positions
      2. Liquid- weaker forces of attraction, mcan form irregular arrangements, more energy so can move in random directions at low speeds
      3. Gases-No attraction between the particles, and the most energy, and are free to move at high speeds
    2. Mainly in solids.
    3. Extra kinetic energy turns into heat
    4. Best in metals because of free electrons
  2. Convection
    1. Liquids and gases only
    2. Circle of heating, travelling then cooling
  3. Heat radiation infrared energy
    1. Bigger surface area, more infrared waves can be emmitted
4. Energy Transfer
  1. Condensation and evaporation
    1. When a gas cools and lose kinetic energy
    2. If it gets close enough the gas becomes a liquid
    3. Vice versa for evaporation
    4. The rate of evaporation is best due to high temperatures, low density, larger surface area, and high airflow
Electricity
1. Cost of Electricity
  1. Energy= Power x time
  2. kWh=Kilowatt-hours
  3. Total energy from two metre readings= subtract the smaller from the end
2. Electrical Appliances
  1. Which one is more cost effective or uses less energy
  2. Standard of living is affected by access to electricity
3. Energy and the Environment
  1. Renewable energy
    1. Wind power- turbines create no pollution, very noisy, rely on wind, high initial cost but no running costs and no permanent damage
    2. Solar Cells- No pollution, but some to create them, very reliable during the day in sunny countries, high initial costs, Expensive to connect to the national grid
    3. Hydroelectric is is used in dams and falling water- expensive and difficult to build, reliable, cheap to connect to the national grid, loss of habitats
    4. Pumped storage is used to save energy
    5. Geothermal and biofuel use heat
  2. Non renewable energy
    1. Creates CO2 through combustion, sulphur dioxide causing acid rain, nuclear waste is dangerous
  3. Comparisons
    1. Initial costs, reliability issues, environmental issues, set up/decommissioning time, running costs, location issues
4. National Grid
  1. Current creates heat so a step up/step down increases voltage to decrease current and vice versa
  2. How electricity is transferred
Waves
1. Basics
  1. Waves have amplitude- height from the middle, wavelength, which is from crest to crest, or frequency in Hz
  2. Transverse waves have sideways vibrations
  3. Longitudinal waves are along the same lines
  4. Wave Speed (m/s)= Frequency (Hz) x Wavelength (m)
2. Refraction + Diffraction
  1. Diffraction - waves spreading out.
    1. When a gap is the same size as wavelength= maximum diffraction
  2. Refraction- changing speed changes direction
    1. Crossing a boundary between 2 substances EG glass to air
3. Electromagnetic Spectrum
  1. Radiowaves Microwaves Infrared Visible Light X-ray Gamma Rays
    1. Radiowaves are used for communication
    2. Microwaves are used for satellite communication and mobile phone
    3. Infrared used for remotecontrols
Origin of the universe
1. Red shift
  1. Light is shifted towards the red end of the spectrum
  2. Shows that everything is moving away from us
2. Big Bang
  1. Cosmic background microwave radiation was origionally gamma rays when the big bang occurred
    1. This has been stretching out since the Big bang proving that the universe is expanding
Efficiency
1. In the home
  1. Short payback time
  2. Cavity wall insulation- stops convection and radiation
  3. Loft insulation stops conduction and radiation
  4. Draught proofing- Reduce convection
  5. Hot water tank jacket-reduces conduction and radiation
  6. Thick curtains- Conduction and radiation
2. Efficiency= Useful Energy Out/ Total energy in
3. Useful energy is concentrated energy
4. The entire energy output of a machine end up as heat
5. Sankey Diagram- Always to scale

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Physics P1 Revision

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