AQA GCSE Physics

Revision Notes

1.1.9 Changes in Energy

Changes in Energy

  • Changes in energy involved when a system is changed could be in many different ways, for example:
    • Heating
    • Work done by forces
    • Work done when a current flows


  • Heating changes the energy stored within a system by increasing the energy of the particles that make up that system
  • This either raises the system’s temperature or, produces a change of state (eg. solid to liquid)
  • An example of the energy change by heating is electrical energy to thermal energy

Heating, downloadable AS & A Level Physics revision notes

Heating a pan on a hob converts an electrical energy store to a thermal energy store

Work Done by Forces

  • Work is done when energy is transferred from one store to another
  • When a force causes an object to move, work is done against frictional forces, causing the object’s temperature to increase and energy is lost as heat and sound to the surroundings
    • For example, a person warms up his hands by repeatedly rubbing them together
  • An example of the energy change by work done by forces is kinetic energy to thermal energy

Work Done Forces, downloadable AS & A Level Physics revision notes

Energy is transferred heat and sound from moving a box

Work Done When a Current Flows

  • Current is the flow of charge
  • A current flows when there is a potential difference applied to the circuit
    • This is provided by the power supply or a cell
  • This gives each charge an amount of energy
    • This is the work done by the power supply when a current flows
  • An example of the energy change by work done when a current flow is chemical energy to electrical energy to thermal energy

Work Done Current, downloadable AS & A Level Physics revision notes

Chemical energy from the battery is converted to electrical energy in the components and then transferred to heat in wires

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