P2b(ii) Generating Electricity You will learn about: How electricity is carried How electricity is made Energy Efficiency

Carrying Electricity There is a network of power cables around the country that transmits electricity. This is known as the National Grid. The National Grid carries electricity to consumers such as homes, farms, schools and hospitals. Electricity is generated in a power station with a voltage of 25,000 Volts. A step-up transformer increases the voltage along the pylon’s transmission lines to 400,000 Volts. From there step-down transformers reduce the voltage until it is safe enough to be used. The mains electricity in our homes uses 230 Volts. So the voltage needs to be stepped down several times before the electricity is carried to our homes. Transformers Step Up : Up the Voltage Step Down: Down the Voltage

Power Station Generators Just like a dynamo, a generator in a power station uses the same ideas: a magnetic field rotates relative to the coil which produces a voltage. In a power station the magnet and coils are much, much larger! In the power station generator the coil of wire is able to rotate freely between the poles of two magnets. When the coil turns it cuts the magnetic field so a current passes through the coil. Just like the dynamo the same would happen if the coil did not move and the magnets did. The generator does not turn by itself. Huge amounts of coal are pulverised and burnt to produce heat. This heat boils water turning it into steam. The steam turns a turbine. The turbine turns the generator. The generator generates electricity. Coal Water Steam Turbine Generator

Efficiency REMEMBER: Due to the size of the power station a lot of energy is wasted. Energy is wasted as heat and sound in the boiler and at the turbine and also in the generator.

Questions 1.A cooling tower in a power station cools what? 2.Define the term ‘consumer’. 3.Describe what happens to water in a power station. 4.A power station has 80% of its energy lost to the environment. How efficient is it? 5.Why do the magnet or coil need to rotate relative to one another? 6. A power station is 40% efficient. It produces 3 million Joules of electrical energy each second. How many Joules of energy are lost to the environment each second?

Questions