Transcript Electricitylesson1

SYSTEMS : ELECTRICITY
Lesson 1:
How important is electricity to us?
Where does it come from?
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.
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?
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.
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.
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)
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.
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
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.
POWER GENERATORS
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 nonrenewable. Once they are gone, they’re gone.
• So, new ways of heating water using renewable
resources are constantly being thought of and used.
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.
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.