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37 Cards in this Set
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P1 Topic 5
Generation & Transmission of Electricity |
If you can answer all of the questions on these cards then you need all you need to know to ace your exam! |
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What is current? |
The current is the rate of flow of charge.
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What is electricity? |
A flow of charged particles.
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What is voltage? |
An electrical pressure giving a measure of the energy transferred.
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What are renewable energy resources?
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Resources that will not run out
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What are solar cells and what are the advantages and disadvantages of using them to generate electicity?
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Solar cells convert solar energy directly into electrical energy. ADVANTAGES: no pollution DISADVANTAGES: solar energy isn't available all the time |
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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 |
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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 |
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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 outADVANTAGES: no pollution, available at predictable timesDISADVANTAGES: not always available, may affect animals that live in those areas, there aren't many places in the UK for i
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What are non renewable resources?
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Sources of energy that will eventually run out.
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What are the advantages of using non renewable sources like fossil fuels?
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* 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 |
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What are the disadvantages of using non renewable sources: fossil fuels?
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* they will all run out one day* they produce pollution, leading to acid rain and climate change
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What are the disadvantages of using non renewable sources: uranium for nuclear power?
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* 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 |
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What factors increase the size of an induced current? |
1. Adding more turns in the coil of wire2. Using a soft iron core3. Using stronger magnets4. Moving the wire faster
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What factors affect the direction of an induced current?
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1. The direction of the movement of the wire 2. The direction of the magnetic field |
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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.
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How do you keep an induced current continuous? |
By keeping the magnet moving relative to the coil of wire.
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How do you produce an electric current on a smale scale e.g. a bicycle dynamo?
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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
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How do you produce an electric current on a large scale e.g. a power station?
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Fossil fuels are burned, creating steam which pushes a turbine and makes it spin- this then turns the generator, producing Alternating Current.
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What is the difference between direct and alternating current?
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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. |
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Which type of current does a generator with carbon brushes create?
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Alternating current
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What does a transformer do?
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Changes the size of alternating voltage.
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Why is electrical energy transmitted at high voltages around the National Grid? |
It improves the efficiency, becuase less energy is wasted as heat
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What do step-up transformers and step-down transformers do?
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Step-up transformers increase the voltage and decrease the current Step-down transformers decrease the voltage and increase the current |
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What is a step-down transformer made up of?
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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.
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Why are transformers used in the transmission of electricity?
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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.
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What are the dangers associated with electricity transmission?
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- 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
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What is the formula for working out the potential difference produced by a transformer?
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Voltage (primary)/ voltage (secondary) = turns (primary) / turns (secondary)Vp/Vs = Np/Ns
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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/Ns230V/23V = 100/?230/23=10also, 100/10=10so, there are 10 turns in the secondary coil
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What is power?
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The energy trasnferred per second, measure in watts
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What are the two formulae for working out power?
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Power(W) = energy used(J) / time(s)Power(W) = current(A) x voltage(V)
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How is energy from the mains supply measured?
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In the kilowatt-hour (kWh)- the amount of energy trasnferred by a 1Kw device in 1 hour.
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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)
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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
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What is payback time and how is it calculated?
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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 |
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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 |
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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 |
