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The National Grid

The National Grid. 6 January, 2020. Keywords Transformers, Power, Voltage, Current, Energy, National Grid, Megawatt, Kilowatt, Joule, Energy. All students should be able to: Draw and label a diagram of the National Grid. Most students should be able to:

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The National Grid

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  1. The National Grid 6 January, 2020 Keywords Transformers, Power, Voltage, Current, Energy, National Grid, Megawatt, Kilowatt, Joule, Energy.

  2. All students should be able to: Draw and label a diagram of the National Grid. Most students should be able to: Describe why electricity is transferred at very high voltages . Some students should be able to: Use power calculations to explain the use of transformers in the National Grid. Outcomes

  3. What is the National Grid?

  4. Watch the demo of the National Grid. Can you answer these questions? When the transformers were not connected what happened to the bulb at the far end of the model? What do the transformers do? Why does the voltage have to be so big in the wires? Demo Time!!

  5. 1 Copy and complete using the key words below: • The National Grid takes …………… from power stations to businesses and homes at extremely large voltages. • It does this to limit the ………….. lost by heat from the wires. • The bigger the electric ………… in a wire, the more heat is lost. • To make the voltages bigger, step up ……………….. are used. To make voltages…………, step down transformers are used. transformerssmallerelectricityenergy current 2 Copy Figure 2 on Page 260 – label the parts and voltages.

  6. What is a transformer? The voltage of an alternating current can be changed using a device called a transformer. iron core A transformer contains two coils that are wound around a soft iron core. The alternating current in the primary (input) coil produces an alternating magnetic field. This alternating magnetic field induces an alternating current in the secondary (output)coil. secondary coil primary coil

  7. Where are transformers used? A television needs a very high voltage to operate. It contains a step-uptransformer, which increases the voltage of the electricity supplied to This outdoor transformer decreases the voltage of the electricity carried by the national grid. It is an example of a step-down the television. transformer.

  8. What is the formula for electrical power? In electrical devices, power can be calculated using the formula: power = current x voltage P =I x V What are the units of power, current and voltage? • Power is measured in watts (W) or kilowatts (kW). • Current is measured in amps (A). • Voltage is measured in volts (V).

  9. Can I use a formula triangle? A formula triangle helps you to rearrange a formula. The formula triangle for P = IV is shown below. Cover up whatever quantity you are trying to find to leave the calculation required. So to find current (I), cover up I… …which gives the formula…   P V I = x

  10. How is power calculated? A power station produces electricity of 2.5 kV 20, 000 A. What is the Power of the Power station? P = IV = 20 000A x 2500 V = 500MW

  11. What is the current running in the wires of the National Grid? I = P/V I = 500 000 000 W/ 400 000V I = 1250 A (A lot less than the 20 000A from the Power Station.) 500MW Power of 500 MW remains constant but Voltage increases to 400 000V. Power Calculations

  12. All Finish Figure 2 on Page 260 – label the parts and voltages. Most Explain why the National Grid uses high voltages in the overhead cables. Some Given the power output of the power station you have drawn is 500MW, what current does it produce? And therefore, from the Voltage that you have labelled in the diagram what is the current through the National Grid? Describe what the transformer has done and why this is useful. SO: from today’s lesson and previous lessons on Electricity Generation answer this: Why have a National Grid? Power – The Big Q: Why have a National Grid?

  13. Plenary

  14. Plenary

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