Energy transfers. Coal is mined and transported to the power station. It is ground into a powder to make it burn quicker. Step 2:

Transcription

1 Energy transfers Name: The national grid system is the energy system that generates electricity and distributes it to consumers. Electricity is generated at a power station and it transfers through pylons and transformers until it reaches your home and can be used. This diagram shows the path these transfers take, from a coal power station. Generating electricity As you go through these steps, fill in the energy transfers on the worksheet: Coal is mined and transported to the power station. It is ground into a powder to make it burn quicker. Step 2: Coal is burnt in a very hot furnace. The heat generated from the fire heats up water which is in a boiler. This creates steam. (Heating by )

2 Step 4: The pressure of the steam builds up and the steam is forced through a pipe to the turbines. Step 5: The turbines have vanes (like a fan) which turn when the steam flows over them. Step 6: As the turbines spin, they turn a magnet inside the generator. The magnet in the generator spins inside a large coil of wire and this generates electricity. After this, the steam that has flowed over the turbines travels through to a condenser where it is cooled down, from gas back into liquid. There is still a lot of heat that needs to be released. This heat is released, with excess steam into the atmosphere from the cooling towers. Distributing electricity

3 As soon as the electricity has been generated, it is distributed through the grid, through large conducting cables. The electricity is transferred to the step-up transformer in a substation. At the stepup transformer, the voltage of the electricity is increased. (It needs to be stepped-up to compensate for voltage that is lost as it travels the long distances through cables, etc.) Step 2: The electricity then travels through the cables that are either underground or overhead on pylons. The electricity is transferred from the cables to a mini-substation which contains a step-down transformer. This reduces the amount of voltage again so that it can be used. Step 4: Finally, the electricity is transferred from the mini-substation to a meter-box and circuit board which controls where this electricity will be distributed in a house i.e. lighting, ring (plugs) and cooking (oven, stove) circuits. Activity 2: Complete this task in your class workbook. Draw your own diagram in your class workbook and annotate (label) each of the steps in the process of generating and distributing electricity. (This is a good activity for the learners to do to summarise in their own minds, each of the steps involved in the process. It also provides them with a study resource to help them prepare for tests and exams.) Dynamos Do you remember how electricity is generated in a generator at a power station? The turbines turn a magnet which is inside a coil of conducting wire and this creates electricity. Some tools and appliances have what we call a dynamo which is a small generator. These appliances only need a small amount of electricity to work so the electricity can be generated in the appliance itself. In a dynamo, kinetic energy is transferred into electrical energy, like in a power station generator. However, unlike a power station generator, this kinetic energy comes from a person using the appliance.

4 In a wind-up radio the person turns a handle and this turns a magnet inside a coil of wire, which generates electricity. When you switch the radio on, sound is produced. Kinetic energy Electrical energy Sound energy In a dynamo torch the person either turns a crank (much like in the wind-up radio), or shakes the torch. In a torch with a crank, electricity is generated the same way as in the radio. In a torch that the person must shake, the magnet travels backwards and forwards through the coil and this generates electricity. When the torch is switched on, light is produced. Kinetic energy Electrical energy Light energy

5 Generating electricity As you go through these steps, fill in the energy transfers on the worksheet: Coal is mined and transported to the power station. It is ground into a powder to make it burn quicker. Step 2: Coal is burnt in a very hot furnace. ( Chemical potential energy Heat energy ) The heat generated from the fire heats up water which is in a boiler. This creates steam. (Heating by conduction ) Step 4: The pressure of the steam builds up and the steam is forced through a pipe to the turbines. ( Heat energy Kinetic energy ) Step 5: The turbines have vanes (like a fan) which turn when the steam flows over them. Step 6: Answer sheet As the turbines spin, they turn a magnet inside the generator. The magnet in the generator spins inside a large coil of wire and this generates electricity. ( Kinetic energy Electrical energy ) After this, the steam that has flowed over the turbines travels through to a condenser where it is cooled down from gas back into liquid. There is still a lot of heat that needs to be released. This heat is released, with excess steam into the atmosphere from the cooling towers.