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Science P1 Topic 5
GCSE edexcel core science physics: generation and transmission of electricity
| Question | Answer |
|---|---|
| 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 |
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