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 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.

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.