# Physics P2

What are the 8 energy stores?
Thermal , Kinetic, Gravitational potential, Elastic, Chemical, Nuclear, Electromagnetic, Electrostatic
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What is energy transfer by heating?
Energy transfer by heating is where energy is transferred from a hotter region to a colder region
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What are the two ways of energy transfer by heating?
Conduction - the vibrating particles of a substance transfer energy to neighbouring particles Convection - where the energetic particles of a substance move away from hotter to cooler regions
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What is meant by the term 'work done'?
Work Done is another way of saying energy transferred
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What are the two ways work can be done?
Work can be done mechanically (an object moving due to a force doing work on it. E.g. pushing, pulling or stretching) or electrically (a charge doing electric work against resistance. E.g. charges moving around a circuit).
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What does the conversation of energy principle say?
The conservation of energy principle says that energy is always conserved: Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
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What is power?
Power is the rate of energy transfer, i.e. how much energy is transferred between stores per second
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What does the total energy transferred (work done) by an electrical appliance depend on?
its power rating and how long the appliance is on for.
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What is the amount of energy transferred electrically given by?
Energy transferred (J) = Power (W) x Time (S)
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How do you calculate the energy in Kwh?
Energy transferred (KWh) = Kilowatts (KW) x Time (H)
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How do you calculate power scientifically and domestically?
Scientific : power(w) = energy(joules) ÷ time(s) Domestic : power(Kw) = energy(Kwh) ÷ time(h)
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How can you improve efficiency?
by lubricating it. You can also improve efficiency of a device by making them more streamlined. Both of these methods reduce unwanted energy transfers caused by work done against frictional forces.
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How can you reduce energy loss in buildings?
Unwanted energy losses by heating can be reduced by using thermal insulation. For example, loft insulation, thick curtains and cavity walls.
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How can the thickness and thermal conductivity of (solid) walls also affect how quickly energy is transferred out of a building?
The thicker the walls, the lower the rate of energy transfer. So thick walls with a low thermal conductivity increases the time taken for a building to cool down.
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How do you calculate efficiency?
Efficiency = useful energy transferred ÷ total energy transferred
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What do sankey diagrams show?
You use Sankey diagrams to show all the energy transfers made by a device; from it you can work out the efficiency of the device
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What are non-renewable resources?
resources that will eventually run out.
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What are the main non-renewable energy sources?
The main non-renewable energy resources on Earth are the three fossil fuels (coal, oil and gas) and nuclear fuels (uranium and plutonium).
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What is an advantage of non-renewable energy sources?
There's always enough fossil and nuclear fuels to meet current demand, and they are extracted from the Earth at a fast enough rate that power stations always have fuel in stock. This means non-renewable power stations can respond quickly to changes
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What is a disadvantage of fossil fuels?
Coal, oil and gas release CO2 into the atmosphere which adds to the greenhouse effect. Coal and oil also releases sulphur dioxide, which causes acid rain.
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How do stream-driven turbines work? (1)
As the fossil fuels burns, the water is heated. The water boils to form steam, which moves and turns a turbine. The turbine is connected to an electrical generator, which generates a potential difference across (and so a current through) a wire
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How do stream-driven turbines work? (2)
by spinning a magnet near the wire. The current produced by the generator flows through the national grid
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What is a renewable energy source?
A renewable energy source is one that will never run out.
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What are the main renewable energy sources?
biofuels, wind, the sun, hydroelectricity and the tides
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How is solar power used?
Solar power is often used in remote places where there's not much choice (e.g. the Australian outback) and to power electric road signs and satellites.
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What are some advantages of solar power?
Initial costs are high but after that the energy is free and running costs almost nothing. There's no pollution when they're being used
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What are the disadvantages of solar power?
They can only generate electricity on a relatively small scale, e.g. in homes. It is most suitable for sunny countries (but can be used in cloudy countries like Britain). Cant produce energy at night or increase production when there's extra demand
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How do you produce hydroelectric power?
Producing hydroelectricity usually involves flooding a valley by building a big dam; Water is stored and allowed out through turbines
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What are the disadvantages of hydroelectricity?
There is a big impact on the environment due to the flooding of the valley and possible loss of habitat for some species. Also, immediate response to increased electricity demand - more water can be let out through the turbines to generate electricit
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What are the advantages of hydroelectricity?
Initial costs are often high but there are minimal running costs and it's a reliable energy source.
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How is wind energy produced?
Each wind turbine has a generator inside it. The rotating blades turn the generator and produces electricity.
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What are the advantages of wind energy?
They have quite a high set-up cost but no fuel cost, no pollution, can be placed offshore to prevent complaints and they produce more electricity there
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What are the disadvantages of wind energy?
They are ugly and spoil the view, can be very noisy, only work when it's windy, so you can't always supply electricity, or respond to high demand.
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What are biofuels?
Biofuels can be made from many different things, from farm waste, animal droppings and landfill rubbish to specifically grown crops (e.g. sugar cane, vegetable oils or trees). They're renewable because we can grow more.
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What is an advantage to biofuels?
They're fairly reliable as they can be generated fairly quickly and easily.
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What is a disadvantage to biofuels? (1)
Burning them releases CO2, expensive, not enough space or water to grow enough crops for food for everyone, species losing their habitats, the decay and burning of this vegetation also increases CO2 and methane emissions,
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What is a disadvantage to biofuels? (2)
hard to respond to immediate energy demands as crops take time to grow (you can stockpile biofuels to combat this)
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What are tidal barrages?
Tidal Barrages are bid dams built across river estuaries with turbines in them. As the tide comes in it fills up the estuary. The water is let out through turbines at set speed.
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What is an advantage of tidal barrages?
There is no pollution, tides are pretty reliable (they happen twice a day)
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What is a disadvantage of tidal barrages?
They affect boat access, they can spoil the view, alters the habitat for wildlife, the tide height is variable and tide barrages don't work when the water level is the same on both sides.
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Why are energy demands changing?
This is down to the population increasing, technological advance (e.g. most homes and workplaces now have computers and electronic devices) and our lifestyles.
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What is the national grid?
a giant web of wires and transformers that covers the UK and connects power stations to consumers (anyone who is using electricity).
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How do transformers work in the national grid?
tep up transformers are used to increase the generated electricity to a very high potential difference (p.d) before it is transmitted through the network of the national grid. Transferring electrical power at a very high p.d. helps to reduce energy
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How do transformers work in the national grid?
losses. The p.d. is then reduced by a step down transformer to a level that is safe for use before being supplied to homes and businesses.
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What are the two types of electrical current?
alternating current (a.c.) and direct current (d.c.).
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What is an a.c. current?
In a.c. supplies the current is constantly changing direction. Alternating currents are produced by alternating voltages in which the positive and negative ends of the potential difference keeps alternating
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What is the Uk domestic supply voltage?
The UK domestic (mains) supply is an a.c. supply at around 230 V.
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What is the frequency of the a.c. mains supply?
The frequency of the a.c. mains supply is 50 cycles per second or 50Hz.
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What is an d.c. current?
Direct current is a current that is always flowing in the same direction. It's created by a direct voltage. This voltage is usually smoothed out to provide a straight line on a graph of p.d. (voltage) against time. cells and batteries supply d.c.
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What are the three wires of a plug?
Earth, live and neutral
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What is the live wire?
It is brown and carries the voltage (p.d.). It alternates between a high positive and a negative voltage of about 230V.
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What is the neutral wire?
It is blue and completes the circuit - electricity normally flows in through the live wire and out through the neutral wire. The neutral wire is always art 0 Volts.
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What is the earth wire?
It is green and yellow and is for safety. It carries the current away if something goes wrong. It's at 0 Volts.
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## Other cards in this set

### Card 2

#### Front

What is energy transfer by heating?

#### Back

Energy transfer by heating is where energy is transferred from a hotter region to a colder region

### Card 3

#### Front

What are the two ways of energy transfer by heating?

### Card 4

#### Front

What is meant by the term 'work done'?

### Card 5

#### Front

What are the two ways work can be done?