Energy and Efficiency

PHYSICS UNIT 1: Energy and Efficency Mindmap

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  • ENERGY AND EFFICIENCY
    • Energy
      • Can be transferred or stored or dissipated
        • But cannot be created or destroyed
      • Devices take in energy in one form and transfer it into another
        • Only part of the energy is usefully transferred
          • Remaining energy is wasted in surroundings
          • E.g. most of a light bulb's energy is wasted as the bulb becomes hot
      • Sankey diagram
        • Shows relative proportions of energy transfer using arrows
    • Efficiency
      • Refers to proportion of energy that is usefully transferred
        • If there is a large proportion of energy usefully transferred
          • ...then the device is more efficient and cost-effective
      • Pay-back time
        • Replacing an old TV may cost £600
          • But also provide an annual saving of £60
            • Pay-back time = £600/£60 = 10 years
      • Efficiency values are expressed as percentages or decimals
        • Efficiency = (useful energy or power out / total energy or power in) x 100%
    • Electrical energy
      • Most energy transferred to houses and industry in this form
      • Easily transferred...
        • By heaters to heat surroundings
        • Into light energy (lamp)
        • Into sound energy (speakers)
        • Into kinetic energy (electric fan)
      • Amount transferred by appliance depends on...
        • How long it is switched on
        • How fast it transfers energy
  • Refers to proportion of energy that is usefully transferred
    • If there is a large proportion of energy usefully transferred
      • ...then the device is more efficient and cost-effective

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