Physics GCSE Energy

Physics GCSE Energy

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  • Created by: Reema
  • Created on: 28-02-12 17:56

The 9 Types of energy

Electrical energy

Light Energy

Sound Energy

Kinetic Energy

Nuclear Energy

Thermal Energy

Gravitational Potential Energy

Elastic Potential

Chemical Energy 

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Efficiency of Machines

Most useful energy transfers involve some losses, often as heat.

1) useful devices are only useful because they can transform energy from one form to another.

2) in doing so, some of the useful input energy is always lost or wasted, often as heat.

3) the less energy that is 'wasted' the more efficient the device is said to be. 

4) the energy flow diagram is pretty much the same for all devices.

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How to calculate efficiency...

Efficiency= useful energy out/total energy in 

Efficiency= useful power out/ total power in

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Efficiency of Machines

(continued)

You have to think about cost-effectiveness as well as efficiency when choosing appliances... 

e.g normal light bulbs or energy efficient light bulbs

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Sankey Diagrams

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/14_2_efficiency.gif)

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Sankey Diagrams

This is what a Sankey diagram looks like. The arrow going in is the input and the two others are output. the arrow going down is wasted energy. 

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The Cost of Electricity

kWh (kilowatt-hours) are units of energy

energy(kWh)= power(kW) x  time(hours)

e.g   0.06kW x 0.5 hours= 0.06 units(kWh)

OR

cost= no. of units x price per unit



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How to read an electricity meter

In the exam they may ask you to read off an electricity meter. The units are usually in kWh but do check.  

You could be given two meter readings and be asked to work out the total energy that has been used over a time period. Just subtract the meter reading at the start of time(the smaller one) from reading at the end to work this out.


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Choosing Electrical Appliances

You may be asked to use data to compare two electrical appliances. Use the previous methods shown to work this out.

Standard of living is affected by access to electricity. Poorer countries' economies' are seriously affected through areas such as communication and public health. 

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Non renewable sources

Non renewable sources

The non renewable sources are 3 fossil fuels and nuclear

  • Coal
  • Oil
  • Natural gas 
  • Nuclear fuels (uranium and plutonium)

1) They will all run out one day.

2) They all damage the environment.

3)However they provide most of our energy

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Renewable sources

The renewables are:

  • wind
  • waves
  • tides
  •  hydroelectric
  • solar
  • geothermal
  • food 
  • biofuels

1) These will never run out

2) Most of them do damage the environment, but less than non renewables

3) They don't provide much energy and can be unreliable as they depend on the weather.

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Nuclear Reactors are just Fancy Boilers...

1) A nuclear power station is mostly the same as the usual but with a nuclear fission of uranium and plutonium producing the heat to make steam to drive turbines, etc. The difference is in the boiler.

2) Nuclear power stations take up the longest time of all power stations to start up. Natural gas power stations take the shortest time of all fossil fuel power stations.

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Solar cells

Solar cells generate electric currents directly from sunlight. Solar cells are the best source of energy for calculators and watches. 

Very reliable in hot countries.

No pollution.

Initially, costs are high, but after this energy is free and running costs almost nil, making it overall much more cost effective. 

Not practical and too expensive to link to the National Grid. 

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Wave Power

  • You need lots of small wave powered turbines located around the coast.
  • As waves come in to the shore they provide an up and down motion which can be used to drive a generator.
  • No pollution. The main problems are spoiling the views and hazards to boats.
  • Quite unreliable. 
  • Initially costs are high.
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Geothermal Energy

  • Heat from underground
  • cost is high
  • not many suitable locations for power plants
  • no environment problems
  • brilliant free energy
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Biofuels

  • made from plants and waste
  • renewable
  • sometimes used in cars
  • can be solids, liquids or gases
  • can be fermented to produce ethanol or plant oils modified to make biodiesel
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Comparison of energy resources

bare in mind when comparing:

  • set up costs
  • reliability issues
  • environmental issues 
  • set up/ decommissioning time 
  • running/fuel costs
  • location issues
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Electricity and the National Grid

  • The National Grid takes electrical energy from power stations to where its needed in homes and industry
  • It enables power to be generated anywhere on the grid, and then to be supplied anywhere else on the grid
  • To transmit the huge amount of power needed, you need either a high voltage or high current
  • The problem with a high current is that you lose a lot of energy through heat in cables
  • It is much cheaper to boost the voltage up high to about 400,000 V and keep the current low
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Pylons and Transformers

  • To get voltage to 400,000 V to transmit the power required transformers as well as big pylons with huge insulators, but its still cheaper
  • the transformers have to step up at one end for efficient and then bring it back down to safe, usable levels at the other end.
  • The voltage is increased(stepped up) using a step up transformer  and then reduced again using a step down transformer


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Supply and Demand

The National Grid needs to generate and direct all the energy the country needs- our energy demands on increasing too.

In order to meet these demands in the future, the energy demands of the consumers will need to decrease

When, say a popular tv show ends, you have to be prepared for several viewers going to make a cup of tea.

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