Energy and Efficiency

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Sankey Diagrams

-Weight is measured in newtons (N). The weight of 1kg object on the Earth's surface is about 10N 

-Energy is measured in Joules (J). The energy needed to lift a weight of 1N by a height of 1 metre is equal to 1 joule 

-A sankey diagram is a digram that shows how we can represent any energy transfer where energy is wasted 

-Becuase energy cannot be created or destroyed;

Imput energy (energy supplied)=useful energy delieverd + energy wasted 

-For any device that transfers energy;

Efficiency= useful energy transferred by the device     (x100%)

                    total energy supplied to the device        

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Improving efficiency

Why machines waste energy:

  • Friction between the moving parts causing heat 
  • The resistance of a wire causes the wire to get hot when a current passes through it 
  • Air resistance causes energy transfer to the surrounding 
  • Sound created by machinery causes energy transfer to the surroundings 

How to reduce the problem;

  • Libricate the moving parts to reduce friction
  • In circuits, use wires with as little electrical resistance as possible 
  • Streamline the shapes of moving objects to reduce air resistance 
  • Cut out noise (e.g tighten loose parts to reduce vibration) 
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