[Music] hi and welcome back to freci lessons. co.uk by the end of this video you should be able to describe how electricity is distributed by the National Grid you should then be able to describe the role of Step Up and step down Transformers in the National Grid we've already seen that we generate electricity in lots of different ways in the UK over 50% comes from burning fossil fuels and 25% from Renewables such as wind power around 20% comes from nuclear power and the remainder is imported from Europe the electricity has to get from the power stations to around 25 million homes in the UK and that's done by the National Grid here's a picture of the National Grid and the key idea is that the National Grid is a system of Transformers and high voltage cables now the National Grid connects the power stations to the homes but remember that only only the Transformers and the cables are actually called the National Grid there's one really big problem getting electricity to homes energy is always lost in the power cables due to the resistance of the wires and the bigger the distance between the power station and the homes the greater the energy loss we can reduce the energy loss by building power stations near to homes but people don't really want to live near power stations the other way is to use Transformers and you could be asked about this in your exams first the electricity from the Power Station passes through step up Transformers and they increase the potential difference to several 100,000 volts now that's because less energy is lost in the power cables when the potential difference is very high now if this comes up in the exam it's really important that you say less energy is lost do not say less electricity is lost because you won't get the mark so the electricity now passes through high voltage cables but this can't be passed onto homes because the potential difference will be far too high so finally the electricity passes through step down Transformers and they reduce the potential difference to around 230 volts and finally this is then passed into homes so here are the key facts the National Grid is a system of Transformers and cables stepup Transformers increase the potential difference and that reduces energy loss in the transmission cables step down Transformers reduce the potential difference before the electricity passes to homes remember you'll find plenty of questions on the National Grid in my vision workbook and you can get that by clicking on the link above okay so hopefully now you can describe how electricity is distributed by the National Grid and then go on to describe the role of Step Up and step down Transformers in the National Grid [Music]