# Energy

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## Heat Transfer

Heat is Transferred in Three Different Ways

1) Heat energy can be transferred by radiation, convection or conduction
2) Radiation is the transfer of heat energy by infra-red waves or IR radiation. IR waves are part of the electromagnetic spectrum so they also have the same properties like travelling through a vacuum at the speed of light. This is important without the need for mater otherwise we would not recieve heat.
3) Conduction and convection involve the transfer of energy by particles
4) Conduction is the transfer of thermal heat energy through a substance without the substance itself moving ( in solids)
5) Convection is the transfer of heat through fluids (liquids and gases) by the upward movement of warmer, less dense regions of fluid.
6) Emission of thermal radiation occurs in solids, liquids and gases. Any object can absorb and emit heat radiation.
7) The
bigger the temperature difference, the faster heat is transferred between it and its surroundings.

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Thermal Radiation involves Emission of Electromagnetic Waves

1) All objects are continually emitting and absorbing heat radiation
2) An object that's hotter than its surroundings emits more radiation than it absorbs ( cools down)
And an object that's cooler than its surroundings absorbs more radiation than it emits ( warms up)

The Amount of Heat Radiated Depends on Surface Area

1) Heat is radiated from the surface of an object
2) The bigger the surface area, the more waves can be emitted from the surface - so the quicker the transfer of heat
3) This is why car and motorbike engines often have "fins" - they increase the surface area so heat is radiated away quicker. So the engine cools quicker
4) It's the same with heating something up - the bigger the surface area exposed to the heat radiation, the quicker it'll heat up

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1) Dark matte surfaces absorb heat radiation falling on them much better than bright glossy surfaces, such as gloss white or silver. They also emit much more heat radiation ( at any given temperature)
2) Silvered surfaces reflect nearly all heat radiation falling on them

MAKING SURE HEAT GETS IN - EX SOLAR HOT WATER PANELS

1) Solar hot water panels contain water pipes under a black surface
2) Heat radiation from the Sun is absorbed by the black surface to heat the water in the pipes.

MAKING SURE HEAT DOESN'T GET IN - EX COOLBAGS

1) In coolbags you want to keep the heat out
2) To minimise heat radiating in, the bag is lined with shiny silver or white material
3) Probably most important though is the insulation to stop conduction
4) Thermos flasks also have silver inner surfaces to keep heat in or out, if they are storing cold/hot liquids.

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MAKING SURE HEAT GETS OUT - EX STOVES

1) The whole point of a wood-burning stove is to heat up its surroundings
2) Painting it matte black means it'll radiate as much heat as possible

MAKING SURE HEAT DOESN'T GET OUT - EX SURVIVAL BLANKETS

1) If someone gets injured halfway up a big snowy hill, it can be crucial to keep them as warm as possible
2) A silver coloured blanket helps to stop their body heat radiating away
3) Also after a marathon, a silver blanket is given to stop cooling down too quickly and getting hypothermia.

Leslie's Cube

The matte black side emits most heat so that side gets the most hottest.

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## Heat Conduction

Conduction of Heat - Occurs Mainly in Solids

CONDUCTION OF HEAT is the process where VIBRATING PARTICLES pass on their EXTRA KINETIC ENERGY to NEIGHBOURING PARTICLES

This process continues throughout the solid and gradually some of the extra kinetic energy (or heat) is passed all the way through the solid, causing a rise in temperature at the other side of the solid. So therefore an increase in the heat radiating from its surface

Metals Conduct Heat Better than Plastic or Wood

- Metals are good conductors as the handles get hot quickly as heat carries on conducting through metal pan handle.
- Wood is a poor conductor as the handle takes much longer to warm up
- Plastic is a poor conductor as the handle takes much longer to warm up

...and it's because of their Free Electrons

1) Metals "conduct" so well because the electrons are free to move inside the metal
2) At the hot end, the electrons move faster and collide with other free electrons, transferring energy.These other electrons then pass on their extra energy to other electrons

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## Heat Conduction continued....

3) Because the electrons can move freely, this is obviously a much faster way of transferring the energy through the metal than slowly passing it between jostling neighbouring particles
4) This is why heat travels so fast through metals

Conduction is more efficient through a short fat rod than a long thin rod.

ENERGY TRANSFERS

No device is 100% efficient and the wasted energy is always evaporated as heat

Example of Energy Transfers

- Microphone/Amplifier/Speaker: Sound -> Electrical -> Sound
- Bow and Arrow: Elastic Potential -> Kinetic

GRAVITATIONAL AND ELASTIC POTENTIAL ENERGY ALWAYS GET CONVERTED INTO KINETIC ENERGY FIRST

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## Conservation of Energy

1) ELECTRICAL Energy...................... --- whenever a current flows
2) LIGHT Energy................................. --- from the Sun,light bulbs, etc
3) SOUND Energy............................... --- from loudspeakers or anything noisy
4) KINETIC Energy............................. --- anything that's moving
5) NUCLEAR Energy............................ --- released only from nuclear reactions
6) THERMAL/HEAT Energy.............. --- flows from hot objects to colder ones
7) GRAVITATIONAL POTENTIAL Energy.. --- possessed by anything which can fall
8) ELASTIC POTENTIAL Energy................... --- possessed by springs, elastic, rubber bands, etc
9) CHEMICAL  Energy....................................... --- possessed by foods, fuels, batteries, etc

Potential and Chemical are Stored Energy because the energy is not doing anything and is waiting to happen

Two Types of Energy Conservation

1) "ENERGY CONVERSATION" is using fewer resources because of the damage they do and because they might run out and is the environmental affect

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## Conservation of Energy/Efficiency

2) "PRINCIPLE OF THE CONSERVATION OF ENERGY" which is that Energy can never be created nor destroyed - It's only ever transferred from one form to another. Is only useful when it can be transferred from one form to another

EFFICIENCY

Most Energy Transfers involve some Losses, often as Heat

1) Useful devices are only useful because they can convert energy from one form to another
2) So some of the useful energy input energy is always wasted or lost, often as heat
3) The less energy that is wasted, the more efficient the device is

Sankey Diagrams

- The thickness of the arrow represents the amount of energy (more efficient) so the thicker the arrow, the more energy it represents (input energy) but there will be several smaller arrows branching off to show different energy transformations.

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## Kinetic and Gravitational Potential Energy

Kinetic Energy is Energy of Movement

- It depends on both the mass and speed, the greater the mass and the faster it's going, the bigger its kinetic energy will be

Kinetic Energy (Joules)  = 1/2 x mass (kg)  x speed (m/s) (squared)

Gravitational Potential Energy is Energy due to Height

GPE is the energy stored in an object of mass (kg) when you raise it to a height (m) against gravity (10 m/s squared)

Gravitational Potential Energy (like stored Kinetic Energy) = m x g x h

(Work has to be done for GPE to increase and that is released when the object falls)

Falling Objects convert GPE into KE

When something falls, its GPE is converted into KE, so the further it falls, the faster it goes

Kinetic Energy gained = Gravitational Potential Energy lost

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## Non-Renewable Energy

Non-renewable energy is one that efficiently cannot be replaced once it has been used and does damage to the environment BUT provides most of our energy.

The non-renewables are the three FOSSIL FUELS and NUCLEAR:

1) Coal
2) Oil
3) Natural Gas
4) Nuclear fuels (uranium and plutonium)
- A nuclear power station is mostly the same as a turbine where nuclear fission produces heat to make steam to drive turbines, etc. The difference is in the boiler:

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## Non-Renewable Energy continued..

Most power stations use steam to drive a turbine because the heat energy released from the fuel is used to heat water to create steam:

Fuel -> Chemical Energy -> Boiler -> Heat Energy -> Turbine -> Kinetic Energy -> Generator -> Electrical Energy -> Grid

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## Nuclear Reactors

1) During the process, Nuclear Energy -> Heat Energy -> Kinetic Energy -> Electrical Energy
2) Nuclear Reactors are expensive to build and maintain and take longer than fossil fuels
3) Processing the uranium before usage can pollute and there are risks of leaks or catastrophes like Chernobyl
4) When they're too old and insufficient, nuclear power stations have to be decommissioned (dismantle and dispose safely and carefully) - this is expensive too
5) Does not produce any of the greenhouse gases.

Red is information in Paper 2

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## Pros and Cons with Non-Renewable Sources

1) Burning fossil fuels releases alot of energy, cheaply
2) There are alot of fossil fuel power stations so we do not need to spend money on new technology
3) Power generated from nuclear processes are "clean" because they do not involve the production of greenhouse or other polluting gases.
4) Nuclear fuel like uranium is relatively cheap

1) All three fossil fuels release Carbon Dioxide into the atmosphere when burned in power stations. All this CO2 contributes to global warming and climate change

2) Burning coal and oil releases sulfur dioxide which causes acid rain and this harms trees, soils and wildlife. Can reduce by taking the sulfur out before it is burned.

3) Coal mining destroys landscape

4) Nuclear waste is dangerous and diffucult to dispose of
5) There are risks of accidents which release radioactive materials in the atmosphere which will cause long-lasting risks to living things

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## Renewable Energy

A Renewable Energy resource is one that will never run out and most of them do damage to the environment but in less nasty ways and the trouble is they do not provide much energy and some of them are unreliable because they depend on weather.

The renewables are:

1) Wind
2) Waves
3) Tidal
4) Hydroelectric
5) Solar
6) Geothermal

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## Proccesses of Renewable Energy Resources

WIND POWER

1) Wind power involves putting alot of wind turbines in exposed places like moors and coastal areas and spoil the view and can be very noisy so noise pollution killing birds and bats
2) Wind turbines convert KE into Electrical Energy and Wind turns the blades, which turns a generator inside it

3) Wind turbines are quite cheap to run because they're tough and reliable
4) Doesn't produce polluting waste
5) The wind isn't strong enugh to generate any power
6) Even though the wind is free, it's expensive to set up a wind farm, especially at sea
7) There's also a problem of no power when the wind stops and it's impossible to increase supply when there's extra demand
8) Intial costs are quite high, but there are no fuel costs and minimal running costs
9) No permanent damage, remove the turbines, the view and noise returns to normal

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## Proccesses of Renewable Energy Resources

HYDROELECTRIC POWER (PG 56 diagram in Edexcel Physics Book)

1) Hydroelectric power requires the flooding of a valley by building a big dam. Rainwater is caught and allowed out through turbines or power stations use the stored GPE of water in high reservoirs built in mountains, converting the GPE of water to KE as it falls which is then converted into Electrical Energy by the generator
2) The energy produces is renewable and the Sun causes the water to evaporate continously and to be drawn up into the atmosphere. This water then falls as rain to be collected in reservoirs and used again.
3) Hydroelectrcity is clean and renewable but building reservoirs and power stations can spoil the landscape. The reservoir can also destroy the natural habitat of wildlife
4) There is no pollution but there's a big impact on environmnet by flooding the valley (rotting vegetation releases methane and CO2)
5) There is an immediate response to increased demand which is a pro and there's no problem with reliability except in times of drought
6) Intial costs are high

Red is Paper 2

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## Proccesses of Renewable Energy Resources

TIDAL POWER (PG 56 diagram in Edexcel Physics Book)

1) Tidal barraiges are big dams built across river estuaries, with turbines in them. As the tide comes in, it fills up the river estuary to a height of several metres. This water can then be allowed out through turbines at a controlled speed. It also drives the turbines on the way in.
2) The kinetic energy of the water is converted into electrical energy by the turbines and a generator
3) The dams affect the rise and fall of water in the estuart and this damages wildlife habitats
4) No pollution,renewable BUT are preventing access for boats and they spoil the view
5) Tides are pretty reliable but the height of the tide is variable so lower tides will provide less energy than higher ones
6) Initial costs are moderately high, but there's no fuel costs

Red is Paper 2

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## Proccesses of Renewable Energy Resources

WAVE POWER

1) Energy can be extracted from waves and the continuous movement of the surface of the seas and oceans in a rise and fall motion of water is used to drive a generator
2) The KE of the waves is converted into electrical energy
3) No pollution,clean (don't produce greenhouse gases) BUT spoil the view and are a harzard to boats
4) Unreliable because waves die out when the wind drops
5) Initial costs are high but no fuel costs and is unlikely to produce energy on a large scale

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## Proccesses of Renewable Energy Resources

SOLAR ENERGY (PG 55 diagrams in Edexcel Physics Book)

1) Solar cells transform light energy from the Sun into electrical energy and they generate direct current (D.C)
2) They are not very efficient and are expensive and require quite bright sunlight to produce useful amounts of electrical energy
3) They are expensive intially but after the energy is free
4) There is no pollution
5) Usually used to generate electricity on a small scale
6) Are used to power calculators and watches
7) Solar panels are basically black water pipes inside a glass box. The glass lets heat (thermal radiation) and light from the Sun in, which is then absorbed by the black pipes and heats up the water
8) Cost money to set up but free fterwards
9 Used for small scale energy production

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## Proccesses of Renewable Energy Resources

GEOTHERMAL ENERGY (PG 54 diagram in Edexcel Physics Book)

1) This is where hot rocks lie quite near the surface. The source of most of the heat is the slow decay of radioactive elements including uranium deep inside the Earth
2) Water is pumped in pipes down to the hot rocks and forced back up due to pressure to turn the turbine which drives a generator so Heat -> KE -> Electrical
3) The hot water is used to provide domestic heating directly and is used for bathing
4) Geothermal energy is also used where there are no hot springs as there are some areas where the rocks beneath the ground are hot enough to produce steam
5) Free and no real environmental problems
6) Cost of drilling down several km is a major drawback (fracking)

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