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The National Grid

The National Grid. Click on logo. What you need to remember from P5:. 1. recall that mains electricity is produced by generators; 2. recall that generators produce a voltage by a process called electromagnetic induction;

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The National Grid

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  1. The National Grid Click on logo

  2. What you need to remember from P5: 1. recall that mains electricity is produced by generators; 2. recall that generators produce a voltage by a process called electromagnetic induction; 3. recall that when a magnet is moving into a coil of wire a voltage is induced across the ends of the coil; 4. recognise that if the ends of the coil are connected to make a closed circuit, a current will flow round the circuit; 5. recall that if the magnet is moving out of the coil, or the other pole of the magnet is moving into it, there is a voltage induced in the opposite direction;

  3. And this…….. 6. explain that a changing magnetic field caused by changes in the current in one coil of wire can induce a voltage in a neighbouring coil; 7. describe the construction of a transformer as two coils of wire wound on an iron core; 8. recall that a transformer can change the size of an alternating voltage; 9. be able to use the equation: 10. describe how, in a generator, a magnet or electromagnet is rotated within a coil of wire to induce a voltage across the ends of the coil;

  4. And this… 11. understand that the size of this induced voltage can be increased by: • increasing the speed of rotation of the magnet or electromagnet; • increasing the strength of its magnetic field; • increasing the number of turns on the coil; • placing an iron core inside the coil; 12. describe how the induced voltage across the coil of a generator changes during each revolution of the magnet or electromagnet and explain that the current produced in an external circuit is an alternating current (a.c.); 13. understand that the current from a battery is always in the same direction: it is a direct current (d.c.); 14. recall that mains electricity is an a.c. supply; 15. explain that a.c. is used because it is easier to generate than d.c., and can be distributed more efficiently; 16. recall that the mains supply voltage to our homes is 230 volts.

  5. Facts that you need to learn

  6. Other relationships: power = potential difference (voltage) × current (watt, W) (volt, V) (ampere, A) energy transferred = power x time (joule, J) (watt, W) (second, s) (kilowatt hour, kWh) (kilowatt, kW) (hour, h) efficiency = energy usefully transferred x 100% total energy supplied

  7. Comprehension questions • What is the National grid? • What is the voltage of electricity produced in power stations? • What does the transformer do to the voltage when the electricity leaves the power station? • What does the transformer do to the voltage when the electricity arrives at the sub-station?

  8. History of the national grid • Who established the principles of alternating high-voltage power distribution? • What did Charles Merz do in 1901? • Where was the first major UK power station? • What is the problem with Britain’s electricity supply in 1925 and what is formed to solve the problem? • What is the frequency of the first nationwide a.c. grid? • What happens to the size of the voltage supply between 1933 and 1965?

  9. Facts and the future • What does ‘GW’ stand for? • What was the most amount of power that needed to be generated in the UK in 2005/6? • How much power could be produced if needed? • How many Exajoules of energy are used every year in the UK? • What was the total amount of power lost? • How many GWs were produced in the north and transferred to the south? What will this figure be in 2014?

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