P1.4.2 The National Grid P1 Physics Mr D Powell

Connection Connect your learning to the content of the lesson Share the process by which the learning will actually take place Explore the outcomes of the learning, emphasising why this will be beneficial for the learner Demonstration Use formative feedback – Assessment for Learning Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex Offer different ways for the students to demonstrate their understanding Allow the students to “show off” their learning Consolidation Structure active reflection on the lesson content and the process of learning Seek transfer between “subjects” Review the learning from this lesson and preview the learning for the next Promote ways in which the students will remember A “news broadcast” approach to learning Activation Construct problem-solving challenges for the students Use a multi-sensory approach – VAK Promote a language of learning to enable the students to talk about their progress or obstacles to it Learning as an active process, so the students aren’t passive receptors

P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid.

What is the National Grid The “grid” is a system of cables which link Power Stations to homes, businesses, industry and other infrastructure. Along the way it has to modify the electrical current to make sure that as much of the energy is delivered as possible. Transformers do the modifications! This diagram shows the main routes.

What is the National Grid This image shows how the grid is split in terms of companies. However, they are still all linked together and sell electricity to each other to meet the demands. This is a fake internal market to allow the system to be privatised and build a profit driven service instead of a nationalised service.

Who produces the power. The power comes from a variety of sources. The map shows all the nuclear power stations The house here is putting energy back into the grid from its solar panels.

Stepping up / Stepping Down 132kV Power station Step up transformer Step down transformer Homes 25kV 230V If we keep the voltage the same all the way and wanted the process to be 90% efficient. Throughout the grid we would have to use cables that were 13cm in diameter! They would weight 7000 tonnes . They If we step up the voltage to 132kV the cables would be 4mm in diameter but we would still only lose 10% of the energy in heat. Also home electricity would be dangerous at such high voltages so it must stepped down anyway.

Revision... Copy the diagram and complete the questions in your books on the National Grid Power station Step up transformer Step down transformer Homes We use the national grid to _ _ _ _ _ _ energy to our homes. The step-up transformers increase the _ _ _ _ _ _ _ _ and reduce the _ _ _ _ _ _. The high voltage electricity now at _ _ _ kV moves with _ _ _ thermal losses and means that the wires can be quite _ _ _ _. Finally the step-down transformers mean that the _ _ _ _ _ is reduced to _ _ _ V and is useable in every day appliances. This can only be done with _ _ _ _ _ _ _ _ _ _ _ from a power station. transfer voltage current 132 low thin voltage 230 alternating current.

M An Argument.... Should power cables be underground or overhead? Here are some of the arguments used: They take up valuable land. They are more difficult to repair. They are more difficult to install across roads, railways and canals. They are much more expensive. They spoil the landscape. They produce electric and magnetic fields that might affect people. Which of the above arguments would you use to argue against: Underground power cables? Overhead power cables? TASK Imagine you are a spokesperson for an environmental group or power company going on live radio. Write down an argument using your own and these ideas from a perspective....

National Grid....

Why do we transform the current and voltage? If we look at this real situation where we are transferring energy down the system. Look at your cases A-E and compare using the table on the sheet. Case Power Transmit /kW Voltage /kV Current /A Power Loss / kW Power received /kW A 400 4 1.6 B C 8 393.6 D E 1

Transformers These are really basic devices we can change the voltage and current at which the energy is transferred. The idea of this is to save power. The simple circuit consists of a Power supply, two bulbs and a transformer. The current to the lower bulb is transferred indirectly by a magnetic field induced in the iron loop. The current has been transformed and p.d. has increased and current reduced http://www.practicalphysics.org/go/Experiment_349.html

Transformers – Results.... The results show an ideal situation where 0.02W are lost due to heating effects 1:3 V, Voltage (V) I, Current (A) P, Power, W 10 Turns (Np) 1.98 0.25 0.5 20 Turns (Ns) 3.96 0.12 0.48 P = VI http://en.wikipedia.org/wiki/Transformer http://www.practicalphysics.org/go/Experiment_349.html

Transformers & everyday uses... Here is an example of how we can transform voltages and currents. The core is the same as in the previous slide but now you can see that the number of turns of wire are different. The ratio of turns either steps up or steps down the voltage. What happens is when the current flow (alternating current) flows back and fourth in one set of wires it creates (induces) a current in the other set of wires. This example is a travel adapter plug!

P1 4.3 National Grid “Quick Test”.... Student Assessed! Basic Demand Connect up these constituent parks in a flow chart to show the “National Grid” in the right order overhead power lines (132kV), step-up transformer, underground cables, homes (230V), step-down transformer, power station 25kV (3 marks) 2. Give two examples of equipment where we use a transformer in the home and explain why for one of them? (3 marks) 4. Explain one disadvantage and advantage of using underground power cables? (2 mark) 5. Why do we step up the voltage so high and then so low for home use? (2 marks) Med Demand ? / 10 High Demand

P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid. P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid. P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid. P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid. P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid. P1.4.2 The National Grid a) Electricity is distributed from power stations to consumers along the National Grid. b) For a given power increasing the voltage reduces the current required and this reduces the energy losses in the cables. c) The uses of step-up and step-down transformers in the National Grid.

P1.4.2 The National Grid P1.4.2 The National Grid

P1.4.2 The National Grid P1.4.2 The National Grid We use the national grid to _ _ _ _ _ _ energy to our homes. The step-up transformers increase the _ _ _ _ _ _ _ _ and reduce the _ _ _ _ _ _. The high voltage electricity now at _ _ _ kV moves with _ _ _ thermal losses and means that the wires can be quite _ _ _ _. Finally the step-down transformers mean that the _ _ _ _ _ is reduced to _ _ _ V and is useable in every day appliances. This can only be done with _ _ _ _ _ _ _ _ _ _ _ from a power station. We use the national grid to _ _ _ _ _ _ energy to our homes. The step-up transformers increase the _ _ _ _ _ _ _ _ and reduce the _ _ _ _ _ _. The high voltage electricity now at _ _ _ kV moves with _ _ _ thermal losses and means that the wires can be quite _ _ _ _. Finally the step-down transformers mean that the _ _ _ _ _ is reduced to _ _ _ V and is useable in every day appliances. This can only be done with _ _ _ _ _ _ _ _ _ _ _ from a power station.

P1.4.2 The National Grid - Worksheet Case Power Transmit /kW Voltage /kV Current /A Power Loss / kW Power received /kW A B C D E C D What do you think? A E B P1.4.2 The National Grid - Worksheet

Case Power Transmit /kW Voltage /kV Current /A Power Loss / kW Power received /kW A 400 100 4 1.6 398.4 B 75 5.3 2.8 397.2 C 50 8 6.4 393.6 D 24 16.6 27.5 372.5 E 1