Mains Electricity
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What is mains electricity?
It is electricity that comes from POWER STATIONS.
Explain how electricity flows from power stations to our homes.
HINT: Draw a sketch. Coal -> Power station -> Step-up transformer -> Pylons -> Step-down substations -> Power lines -> Electricity box -> Homes -> Wall socket -> Appliance -> Reverse -> Power station • Electricity is made at the POWER STATION. • Most power stations use COAL as a source of energy. • Electricity from the power station is sent to STEP-UP TRANSFORMERS. • These transformers INCREASE the power of electricity. • This helps send electricity over LONG distances. • Electricity travels from the transformer along PYLONS (which are transmission lines and towers) through the country. • These pylons form a GRID of wires across the country called the NATIONAL GRID. • When the electricity reaches a STEP-DOWN SUBSTATION, its power is DECREASED. • Electricity is then sent on smaller POWER LINES to an ELECTRICITY BOX at our homes. • This box measures how much electricity we use. • The box is full of wires and switches that CONTROL THE FLOW of electricity in our home. • From the electricity box, the electricity flows through WIRES to WALL SOCKETS in the wall. • We plug our appliances into these wall sockets and the electricity flows into it. • Once the appliance uses the electricity, if flows BACK TO THE POWER STATION in reverse. • The cycle starts again. TAKE A LOOK AT DIAGRAM IN CLASSWORK / TEXTBOOK.
Why are STEP-D0WN substations important?
They are needed to DECREASE the power of the electricity before reaching our homes. If not decreased, the electricity could damage our appliances.
Where do power stations get their energy from?
In SA, most power stations use COAL.
Why do power stations in SA use coal as their source of energy?
There is an abundance (a lot) of coal.
Where does coal come from?
Coal comes from FOSSILISED bodies of PLANTS and ANIMALS. It takes about 440 MILLION years to make coal.
Where are most of SA’s power stations located?
Mpumalanga.
How do power stations use coal to make electricity?
• The power stations BURNS the coal. • ENERGY is released from the coal in the form of HEAT. • This heat is used to make ELECTRICITY.
Name 5 other sources of energy for making electricity.
• Water: Hydro-electric power • Wind: Wind turbines • Nuclear: Nuclear power plants (eg. Koeberg) • Gas: Gas turbines • Sun: Solar panels
What happens at STEP-UP TRANSFORMERS?
The transformers increase the power of electricity. This helps send the electricity over long distances.
What is the function of the electricity box?
It MEASURES how much electricity we use. It CONTROLS the flow of electricity.
What is the National Grid?
Pylons, which are transmission lines and towers, that form a GRID of wires across the country.