Using Energy and Electrical Energy.

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Key points over the whole topic. Forms of energy

  • Energy exists in different forms.
  • Energy can change into one form into another form.
  • When an object falls and gains speed, its gravitational potential energy decreases and its kinetic energy increases.

Conservation of energy

  • Energy cannot be created or destroyed.
  • Conservation of energy applies to all energy changes

Useful Energy

  • Useful energy is energy in the place we want it and in the form that we need it.
  • Wasted energy is energy that is not useful energy.
  • Useful energy and wasted energyboth end up being transferred to the surroundings, which becomes warmer.
  • As energy spreads out, it gets more and more difficult to use for further energy transfers.

Energy and efficiency

  • The efficiency of a device = useful energy transferred by the device ÷ total energy aupplied to the device (x100%)
  •  No machine can be more than 100% efficient.
  • Measures to make machines more efficient include reducing friction, air resistance, electrical resistance and noise due to vibrations.

Electrical Appliances

  • Electrical appliances can transfer electrical energy into useful energy at the flick of a switch.
  • Uses of everyday electrical appliances including heating, lighting, making objects move (using an electric motor) and creating sound and visual images.
  • An electrical appliance is designed for a particular purpose and should waste as little energy as possible.

Electrical power

  • Power is rate of transfer of energy.
  • You can calculate  power using P=E/T
  • Efficiency = useful power out/total power in (x100%)

Using electrical energy

  • The kilowatt-hour is the…


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