Energy:

  • Define a system as an object or group of objects and state examples of changes in the way energy is stored in a system
  • Describe how all the energy changes involved in an energy transfer and calculate relative changes in energy when the heat, work done or flow of charge in a system changes
  • Use calculations to show on a common scale how energy in a system is redistributed
  • Calculate the kinetic energy of an object by recalling and applying the equation: [ Ek = ½mv2 ]
  • Calculate the amount of elastic potential energy stored in a stretched spring by applying, but not recalling, the equation: [ Ee= ½ke2 ]
  • Calculate the amount of gravitational potential energy gained by an object raised above ground level by recalling and applying, the equation: [ Ee = mgh ]
  • Define power as the rate at which energy is transferred or the rate at which work is done and the watt as an energy transfer of 1 joule per second
  • Calculate power by recalling and applying the equations: [ P = E/t & P = W/t ]
  • Explain, using examples, how two systems transferring the same amount of energy can differ in power output due to the time taken
  • State that energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed and so the total energy in a system does not change
  • Explain that only some of the energy in a system is usefully transferred, with the rest ‘wasted’, giving examples of how this wasted energy can be reduced
  • Explain ways of reducing unwanted energy transfers and the relationship between thermal conductivity and energy transferred
  • Describe how the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls
  • Required practical 2: investigate the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material.
  • Calculate efficiency by recalling and applying the equation: [ efficiency = useful power output / total power input ]
  • Suggest and explain ways to increase the efficiency of an intended energy transfer
  • Describe how appliances transfer energy to the kinetic energy of motors or the thermal energy of heating devices