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Science P1 Topic 5

GCSE edexcel core science physics: generation and transmission of electricity

QuestionAnswer
What is current? The current is the rate of flow of charge.
What is electricity? A flow of charged particles.
What is voltage? An electrical pressure giving a measure of the energy transferred.
What are renewable energy resources? Resources that will not run out
What are solar cells and what are the advantages and disadvantages of using them to generate electicity? Solar cells convert solar energy directly into electrical energy. ADVANTAGES: no pollution DISADVANTAGES: solar energy isn't available all the time
What is hydroelectricity and what are the advantages and disadvantages of using it to generate electicity? It is generated by releasing water trapped in resevoirs & allowing it to fall and turn turbines. ADVANTAGES: it is available all the time, can be started and stopped easily DISADVANTAGES: only in places where water can be trapped in high resevoirs
What are wind turbines and what are the advantages and disadvantages of using them to generate electicity? Wind turbines use kinetic energy from wind and turn it into electrical energy. ADVANTAGES: no pollution DISADVANTAGES: they "ruin the landscape" for some people, the wind has to be not too slow or fast, only produce a little bit of electricity
What is tidal power and what are the advantages and disadvantages of using it to generate electicity? Turbines in a big dam across an estuary turn as the tides flow in and out ADVANTAGES: no pollution, available at predictable times DISADVANTAGES: not always available, may affect animals that live in those areas, there aren't many places in the UK for i
What are non renewable resources? Sources of energy that will eventually run out.
What are the advantages of using non renewable sources like fossil fuels? * they produce large amounts of energy (it takes many windturbines to produce the same amount of energy as 1 power station) * they aren't weather dependant * they are quite cheap * there is still a good supply of fossil fuels at the moment
What are the disadvantages of using non renewable sources: fossil fuels? * they will all run out one day * they produce pollution, leading to acid rain and climate change
What are the disadvantages of using non renewable sources: uranium for nuclear power? * they produce radioactive waste that has to be buried and sealed safely * the station has to be decommissioned at the end of its life- which is very expensive- so that no radioactive materials escape * there could be a radioactive leak
What factors increase the size of an induced current? 1. Adding more turns in the coil of wire 2. Using a soft iron core 3. Using stronger magnets 4. Moving the wire faster
What factors affect the direction of an induced current? 1. The direction of the movement of the wire 2. The direction of the magnetic field
What is electromagnetic induction? When you put a piece of wire in a magnetic field, an electric current will flow in the wire- the induced current.
How do you keep an induced current continuous? By keeping the magnet moving relative to the coil of wire.
How do you produce an electric current on a smale scale e.g. a bicycle dynamo? A magnet spins inside a coil of wire which induces a Direct Current (DC). The current is then used to light up the bicycle lights
How do you produce an electric current on a large scale e.g. a power station? Fossil fuels are burned, creating steam which pushes a turbine and makes it spin- this then turns the generator, producing Alternating Current.
What is the difference between direct and alternating current? Direct current flows in only one dirrection, and looks like a straight line on an oscilloscope. Alternating current constantly changes direction and looks like a wavy line on an oscilloscope e.g. mains supply.
Which type of current does a generator with carbon brushes create? Alternating current
What does a transformer do? Changes the size of alternating voltage.
Why is electrical energy transmitted at high voltages around the National Grid? It improves the efficiency, becuase less energy is wasted as heat
What do step-up transformers and step-down transformers do? Step-up transformers increase the voltage and decrease the current Step-down transformers decrease the voltage and increase the current
What is a step-down transformer made up of? It is an iron core with a set of coils of wire on either side. In a step-down transformer, the primary coil will have more coils, and the secondary coil will have less coils.
Why are transformers used in the transmission of electricity? They are used because the voltage needs to be increased when it comes out of a power station- to increase efficiency when passed around the country- however as it enters houses and offices, it needs to be decreased to 230V for safety.
What are the dangers associated with electricity transmission? - Electricity supplied to homes at 230V can kill you - You can get an electric shock if one part of your body is at a higher voltage than another e.g. if you fly a kite ande it touches a pylon, it would kill you
What is the formula for working out the potential difference produced by a transformer? Voltage (primary)/ voltage (secondary) = turns (primary) / turns (secondary) Vp/Vs = Np/Ns
A TV runs off mains supply but only needs 23V- the transformed has 100 turns in the primary coil, how many in the secondary? Vp/Vs = Np/Ns 230V/23V = 100/? 230/23=10 also, 100/10=10 so, there are 10 turns in the secondary coil
What is power? The energy trasnferred per second, measure in watts
What are the two formulae for working out power? Power(W) = energy used(J) / time(s) Power(W) = current(A) x voltage(V)
How is energy from the mains supply measured? In the kilowatt-hour (kWh)- the amount of energy trasnferred by a 1Kw device in 1 hour.
How can you work out the cost of electricity using power, time and the cost of 1kWh? Cost(pence) = power(kW) x time(h) x cost of 1kWh(p/kWh)
What are the advantages of low energy appliances? * They use less energy, which has to be generated through burning fossil fuels, which contributes to global warming * They can save you money
What is payback time and how is it calculated? pPayback time is the length of time it takes you to save up the amount of money it cost to buy the item- the most co-efficient method has the shortest payback time. Payback time = cost / savings per year
What are some examples of how to save energy around the house? Double glazing on windows, cavity-wall insulation, solar panels for hot water, draftproofing for under the front door
If solar panels cost £3500 and your savings are £70 a year, how long will it ake you to save the money that it cost you to buy thm? Payback time = £3500 / £70 = 50 years
Created by: 11043
 

 



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