Energy and Efficiency

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  • Created by: XxzoexX
  • Created on: 01-05-14 17:56

types of energy

  • Gravitational potential
  • kinetic
  • heat
  • strain
  • light
  • nuclear
  • chemical
  • elastic potential
  • electrical
  • sound

We can change all energy from one type to another (IN--OUT)

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conservative of energy

Energy in=Energy out


Useful and wasted energy

useful and wasted energy is the energy that comes out.

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Sankey diagram

Sankey Diagram

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What is efficiency?

  • How much useful energy you get out compared to energy put in

How to calculate efficiency

E.g. A light bulb gives out 50J of light, if 400J of electrical energy is put in calculate efficiency

Efficiency= 50/400 =0.125


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Energy and power

  • All electrical appliances use electrical energy
  • The power rating(w) tells us how much energy an appliance uses every second

e.g. 40w=40 joules per second

E=p x t

Energy transfer(J)=Power(w) x time(s)

E.G. a 1800w hairdryer is used for 10 minutes. Caluculate energy transfer,give the units.

E=p x t

1800 x 600 =1080000J

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Electrical energy

  • The kilowatt hour is a unit electricity meters record the mains electrical energy transformed into units of kilowatt hour.One kilowatt hour is the energy transformed by kilowatt devices in 1 hour.

E.G. A 3 kilowatt electrical kettle is used 6 times for 5minutes each time.

3kw x 30/60=1.5

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