Download - SYSTEMS : ELECTRICITY Lesson 1: How important is electricity to us? Where does it come from?
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SYSTEMS : ELECTRICITY
Lesson 1:
How important is electricity to us?
Where does it come from?
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How important is electricity?• Electricity figures everywhere in our
lives.
• Let’s start the lesson spinning a yarn.
• The story begins like this:– I woke up one morning and my mummy
told me that the Government in their bid to conserve electricity has declared that day a no-electricity day. Yes, there would be no electricity at all.
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How important is electricity?– I went to the bathroom and as it was only
5.45am in the morning, the bathroom was pitch dark. I automatically reached out to switch on the light but there wasn’t light. How was I to do my business if I couldn’t see?
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How important is electricity?• Ending
– By the end of the day, I was tired, frustrated and hoping that electricity could be restored and my prayers were answered. When the light flickered on in my room, I almost wanted to embrace the switch.
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Where do we get our electricity from? • There are several sources of electricity but we will
focus on the power generator today.
• An electric generator is a device for converting mechanical energy into electrical energy.
• The process is based on the relationship between magnetism and electricity.
• When a wire or any other electrically conductive material moves across a magnetic field, electricity flows in the wire.
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POWER GENERATORS
•This generator is based on the principle of “electromagnetic induction” discovered in 1831 by Michael Faraday, a British scientist.
•To make electricity therefore, we need to somehow keep turning the coil of wire.
•The normal way is to use a turbine which is a fan in reverse (Wheel and axle)
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POWER GENERATORS• But what turns the turbine then?
• Wind generators are probably the easiest type of power station to understand.
• Advantages : •Clean and damage the environment very little
• Disadvantages:•Unsightly
•Produce a lot of noise
•Rarely built in inhabited areas – power must be transmitted long distances and power is lost.
•Wind is not controllable and not always available.
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POWER GENERATORS• The next easiest to understand type of power station
is the hydroelectric station.
• Here the turbine is driven by moving water rather than moving air.
• http://people.howstuffworks.com/hydropower-plant.htm
• Advantage:
•Turned on very quickly, within seconds, sudden increase in supply of electricity
•Renewable resource
• Disadvantage:•Depends on where the river is and again long transmission distance
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POWER GENERATORS• The third and by far the most important way of
driving the turbines is steam.
• In a power plant, there are big boilers that burn a fuel to make heat so that steam is produced when the water has boiled. The steam is then piped to the turbine through very thick pipes.
• The steam is fed under high pressure to the turbine which spins and its shaft is connected to the turbogenerator.
• First disadvantage is that a lot of CO2 is produced.
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POWER GENERATORS
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POWER GENERATORS• The question next is what is burnt to produce the
heat.
• The fuel used is usually wood, coal, oil or natural gas.
• These fuels are the remains of plants and animals that lived million of years ago. It takes many years to form and cannot last forever. Such fuel is non-renewable. Once they are gone, they’re gone.
• So, new ways of heating water using renewable resources are constantly being thought of and used.
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POWER GENERATORS
• Nuclear power plants use nuclear energy to heat water. (small amounts of extremely hazardous waste)
• Geothermal power plants use steam or hot water found naturally below the earth’s surface without burning a fuel.
• Hydroelectric power stations uses flowing water to spin the turbine.
• Solar power, wind power, tidal energy or biomass are also used.
• Each has its advantages and disadvantages.
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WEBSITES TO VISIT FOR MORE INFORMATION
• Much of the information in these slides have been extracted from the following websites:
• http://www.energyquest.ca.gov
• http://www.science.howstuffworks.com/battery.htm
• http://www.science.howstuffworks.com/solar-cell.htm
• http://www.eia.doe.gov/kids/electricity.html
• http://www.bbc.co.uk/dna/h2g2/alabaster/A715637 (how power stations work)
• Please go to the above websites for more detailed information about electricity.