GCSE Science Energy 1B

• Electrical appliances transfer electrical energy into other forms 
• The amount of energy that is transferred by an appliance depends on its power and the amount of time the appliance is switched on 
• Energy is usually measured in joules (J) 
• Power is usually measured in watts (W) or kilowatts (kW) 
• When you're dealing with large amounts of electrical energy it is easier to think of the power and time in kilowatts and hours, rather than watss and seconds 
• So the standard units of electrical energy are kilowatt-hours (kWh) not joules   

• In the exam they may ask you to think and compare the pros and cons of different appliances and which is most suitable for a particular situation 
• You need to work out whether one is more cost effective and uses less energy 
• Also about the practical advantages and disadvantages 

Standard of living of affected access to electricity

•  Many people living in the world's poorest countries don't have access to electricity, this affects their standard of living 
• In the UK, our houses are full of devices that transform electrical energy to other useful types of energy 
• Refrigerators keep food fresher for longer by slowing down the growth of bacteria, they are also used to keep vaccines cold. Without out it would be difficult to distribute important vaccines
• Hospitals in developed countries rely on electricity, without the working machines the diagnosis and treatment of patients would be poorer and could reduce life expectancy 
• Communications are affected also, without electricity for use of Internet or phones it would be hard for people to keep in touch    

There are 12 different types of energy resources, these fit into the two subcategories, renewable and non-renewable 

Non-renewable energy resources will run out one day 

• Coal 
• Oil
• Natural Gas
• Nuclear fuels  
  • They will all run out one day 
  • They will do damage to the environment 
  • But they provide most of our energy 

Renewable energy resources will never run out

• Wind
• Waves
• Tides
• Hydroelectric
• Solar
• Geothermal
• Food
• Biofuels 
  • These will never run out 
  • Most of them do damage the environment, but in less nasty ways than non-renewable 
  • They don't provide much energy and some are unreliable as they depend on the weather 

Most of the energy we use is generated from the non-renewable resources

The basic features of a typical power station

• The fossil fuel is burned to convert its stored chemical energy into heat 
• The heat energy is used to heat water to produce steam
• The steam turns the turbine, converting heat energy into kinetic energy
• The turbine is connected to a generator, which transfers kinetic energy into electrical energy 

•  A nuclear power station is similar to a typical power station but with nuclear fission of uranium or plutonium producing the heat to make steam to drive turbines
• Nuclear power stations take the longest time to start up whereas natural gas power stations take the shortest 

Renewable energy resources will not run out and they do less damage to the environment, but they don't generate as much electricity as non-renewables 

• Wind Power involves putting up lots of wind turbines up in exposed places like on moors or round coasts
• Each wind turbine has its own generator inside it. The electricity comes when the wind turns the turbines which then turns the generators producing electricity 
• There's no pollution 
• But they spoil the view and affects the scenery 
• They can very noisy, which can be bad for those living nearby 
• There is a big problem when the wind stops and you cannot increase the supply 
• The starting costs are high but there are no fuel costs
• There's no permanent damage to the environment   

• Solar cells generate electric currents directly from the sunlight. They are the best to use in calculators and watches which don't use much electricity 
• Solar power is often used in remote places where there's not much choice and to power electric road signs and satellites
• There's no pollution 
• In sunny countries solar power is very reliable but only during the day, but it can still be cost-effective in countries like the UK 
• Initial costs are high but after that energy is free and running costs nil 
• Solar cells are usually used to generate electricity on a relatively small scale 
• It's often not practical or too expensive to connect them to the National Grid   

Water can be used to turn turbines in the same way as wind, wherever it is moving we can transfer its kinetic energy to electrical energy

• Hydroelectric power usually requires the flooding of a valley by building a big dam 
• Rainwater is caught and allowed out through turbines. There is no pollution
• But there is a big impact on the environment due to the flooding resulting in loss of habitats or species. They can unsightly when they dry up 
• Putting them up remote villages tends to reduce their impact on humans  
• A big advantage is it can provide an immediate response when an increases in demand 
• There's no problem with reliability except in times of drought 
• Initial costs are high but there's no fuel and minimal running costs 
• It can be useful to generate electricity on a small scale in remote areas 

• Most power stations have huge boilers which have to be kept running all night even though demand is very low. This means there's a surplus of electricity at night 
• It difficult to find a way of storing this pare energy for later use 
• Pumped storage is one of the best solutions 
• In pumped storage, spare night-time electricity is used to pump water up to a higher reservoir 
• This can then be released quickly during periods of peak demand such as teatime to supplement the steady delivery from the big power stations 

• Wave Power - you need lots of small energy wave-powered turbines located around the coast 
• As waves come in to the shore they provide an up and down motion which can be used to drive a generator
• There's no pollution. The mains problems are spoiling the view and being a hazard to boats 
• Initial costs are high, but there are fuel costs. Wave power is never likely to provide energy on a large scale 

• Tidal Power - tidal barrages are big dams built across river estuaries with turbines in them
• As the tide comes in it fills up the estuary to a height of several metres it also drives the turbines. This water can then be allowed out through the turbines at a controlled speed
• The source of the energy is the gravity of the Sun and the Moon 
• There is no pollution. The main problems are preventing free access by boats, spoiling the view and altering the habitat of wildlife
• Tides are pretty reliable in the sense that they happen twice a day without fail and always near the predicted height. The only drawback is that the height is variable and it doesn't work when the water level is the same on both sides of the barrages - this happen four times a day. But they are good for storing energy ready for demand
• Initial costs are moderately high, but there are no fuel cots and minimal running costs. Even though it can only be used in the most suitable places, tidal power has the potential for generating a significant amount of energy 

Geothermal Energy, heat from underground 

• This is only possible in volcanic areas where hot rocks lie quite near to the surface. The source of the heat is the slow decay of various radioactive elements deep inside the earth
• Steam and hot water rise to the surface and are used to drive a generator 
• This is free energy and with no environmental problems 
• In some places, geothermal heat is used to heat buildings directly, without being converted into electrical energy
• The main drawback with geothermal energy is that there aren't many suitable places for power plants
• Also, the cost of building a power plant is much higher compared to the amount of energy we get out of it   

Biofuels are made from plants and waste

• Biofuels are renewable energy resources. They're used to generate electricity the same way as fossil fuels, they're burnt to heat up water 
• Like fossil fuels, they can be used in cars 
• Biofuels can be solids,liquids or gases 
• We can get biofuels from living organisms or dead organic matter, like fossil fuels, but from organisms that have been living much more recently  

Non-renewables are also linked to other environmental problems 

• All three fossil fuels (coal, oil and gas) release carbon dioxide in the atmosphere when they are burned. Coal releases more carbon dioxide at the same amount of energy followed by oil then gas. All this carbon dioxide adds to the greenhouse effect and contributes to global warming 
• Burning coal and oil releases sulfur dioxide, which causes acid rain. Acid rain can be harmful to trees and soils and can have bad effects on ecosystems 
• Acid rain can be reduced by taking out the sulfur or cleaning the emissions 
• Coal mining makes a mess of the landscape
• Oil spillages causes serious environmental problems as they affects mammals and sea creatures
• Nuclear power is clean,  but nuclear waste is very dangerous and difficult to dispose of
• Nuclear fuel is relatively cheap but the cost of nuclear power is high
• Nuclear power always carries the risk of a major catastrophe  

Biofuels have their disadvantages too

• Biofuels are a relatively quick and natural source of energy and are supposedly carbon neutral 
• In some regions, large ares of forest have to be cleared to make room to grow biofuels, resulting in many species losing their habitats. The decay and burning of this vegetation increases carbon dioxide and methane emissions 
• Biofuels have potential, but their use is limited to the amount of farmland available  

Carbon capture can reduce the impact of carbon dioxide 

• Carbon capture (CCS) is used to reduce the amount of carbon dioxide building up in the atmosphere and reduce the strength of the greenhouse effect 
• CCS works by collecting the carbon dioxide from power stations before it is released into the atmosphere 
• The captured carbon dioxide can then be pumped into empty gas fields like those under the North Sea. It can be safely stored without adding to the greenhouse effect 

Because coal and oil are running out, many of theses old power stations are being taken out of use 

• Set-up Costs - renewable resources need bigger power stations than non-renewables for the same output.The bigger the power station the more expensive it is. 
  • Nuclear reactors and hydroelectric dams also need huge amounts of engineering to make them safe, which bumps up the cost 
• Reliability Issues - non-renewables are reliable energy except when they run out 
  • Many of the renewable sources depend on weather which means they are unreliable here in UK. The exceptions are tidal power and geothermal which don't depend on weather 
• Running/Fuel Costs - renewables usually have the lowest running costs because there is no actual fuel involved 

• Environmental Issues - Atmospheric Pollution: Coal, Oil and Gas
  • Visual Pollution: Coal, Oil, Gas, Nuclear, Tidal, Waves, Wind and Hydroelectric 
  • Other Problems - Nuclear (dangerous waste, explosions and contamination) Hydroelectric (bursting dams) 
  • Using Up Resources - Coal, Oil, Gas and Nuclear
  • Noise Pollution - Coal, Oil, Gas, Nuclear, Wind
  • Disruption of Habitats - Hydroelectric, Tidal and Biofuels 
  • Disruption of Leisure - Activities (boats) Waves and Tidal 
• Set-Up/Decommissioning Time - Both affected by size of power station, complexity of engineering and planning issues. 
  • Gas is the quickest to start up and Nuclear power the longest to decommission 

• Location Issues - Solar, pretty much everywhere, though the sunnier the better
  • Gas - pretty much anywhere there's piped gas 
  • Hydroelectric - hilly, rainy places with floodable valleys 
  • Wind - exposed, windy places like moors and coasts or out to sea
  • Oil - near the coast 
  • Waves - on the coast
  • Coal - near coal mines 
  • Nuclear - away from people but near water 
  • Tidal - big river estuaries where dams can be built
  • Geothermal - fairly limited, only in places where hot rocks are near the Earth's surface 

The National Grid is a network of pylons and cables that covers all of the UK, getting electricity to homes everywhere 

• The National Grid takes electrical energy from power stations to where it's needed 
• It enables power to be generated everywhere on the grid
• To transmit the huge amount of power needed, you need either a high voltage or a high current 
• The problem with a high current is that you lose loads of energy through heat in the cables 
• It's much cheaper to boost the voltage really high and keep the current low 
• To get voltage to 400 000V to transmit power requires transformers as well as big pylons with huge insulators but it's still cheaper 
• The transformers have to step up the voltage up one end, for efficient transmission and then bring it back down to safe, usable levels at the other end 
• The voltage is increased using a step-up transformer
• It's then reduced again at a consumer using a step-down transformer   

• Electrical energy can be moved around by cables buried in the ground, as well as overhead power lines 
• The National Grid needs to generate and direct all the energy that the country needs our energy demands keep on increasing too
• In order to meet these demands in the future, the energy supplied to National Grid will need to increase, or the energy demands of consumers will need to decrease
• In the future, supply can be increased by opening more power plants or increasing their power output, or both 
• Demand can be reduced by consumers using more energy-efficient appliances and being careful not to waste energy in the home  

Waves transfer energy from one place to another without transferring any matter

• The amplitude is the displacement from the rest position to the crest 
• The wavelength is the length of a full cycle of the wave 
• Frequency is the number of complete waves passing a certain point per second OR the number of waves produced by a source each second. Frequency is measured in hertz (Hz) 1Hz is one wave per second 

Transverse waves have sideways vibrations

• Light and all other EM waves 
• Ripples on water
• Waves on strings 
• A slinky spring wiggled up and down 

In transverse waves the vibrations are perpendicular (at 90) to the direction of energy transfer of the wave  

Longitudinal waves have vibrations along the same line 

• Sound waves and ultrasound 
• Shock waves 
• A slinky spring when you push the end 

In longitudinal waves the vibrations are parallel to the direction of energy transfer of the wave

Wave = Frequency * Wavelength    

• This equation applies to all waves
• The speed of a wave is usually independent of the frequency or amplitude of the wave   

All waves can be reflected, refracted and diffracted 

• When waves arrive at an obstacle their direction of travel can be changed 
• This can happen by reflection, refraction or diffraction 

Reflection of light lets us see things 

• Reflection of light is what allows us to see objects. Light bounces off them and into our eyes 
• When light travelling in the same direction reflects from an uneven surface the light reflects off at different angles 
• When light travelling in the same direction reflects from an uneven surface then it is all reflected at the same angle and you get a clear reflection 
• The law of reflection applies to every reflected ray 

Angle of incidence = Angle of reflection 

• Waves can be refracted which means they go through a new material but change direction 
• Or they can be diffracted the waves bend round obstacles, causing the waves to spread out 

Diffraction, waves spreading out 

• All waves spread out at the edge when they pass through a gap or pass an obstacle 
• The amount of diffraction depends on the size of the gap relative to the wavelength of the wave. The narrower the gap, or the longer the wavelength, the more the wave spread out 
• A narrow gap is one that is the same order of magnitude as the wavelength of the wave 
• So whether a gap counts as narrow or not depends on the wave in question 
• Light has a very small wavelength so it can be diffracted but it needs a really small gap  

Refraction, changing the speed of a wave can change its direction

• When a wave crosses a boundary between two substances it changes direction
• When light shines on a glass window pane, some of the light is reflected, but a lot of it passes through the glass and gets refracted as it does so 
• Waves are only refracted if they meet a new medium at an angle 
• If they're travelling along the normal they will change speed but are not refracted - they will not change direction     

Types of electromagnetic (EM) waves have a lot in common but their differences make them useful to us in different ways 

• EM waves with different wavelengths ( or frequencies) have different properties. We group them into seven basic types, but the different regions actually merge to form a continuous spectrum 
  •  EM waves vary in wavelength from around 10(-15)m to more than 10(4)m 
  • All the different types of EM wave travel at the same speed (3*10(8)m/s) in vacuum (space) 
  • EM waves with higher frequencies have shorter wavelengths 
  • Because of their different properties, different EM waves are used for different purposes  

Radio waves are mainly used for communication 

• Radio waves are EM radiation with wavelengths longer than about 10cm 
• Long-wave radio (wavelengths of about 1-10km) can be transmitted from London and received halfway around the world. This is because long wavelengths diffract around the curved surface of the Earth 
• Long-wave radio wavelengths can also diffract around hills, into tunnels and more 
• This diffraction effect makes it possible for radio signals to be received even if the receiver isn't in line with the transmitter 
• The radio waves used for TV and FM radio transmissions have very short wavelengths. To get reception you be in direct sight of the transmitter - the signal doesn't bend around hills or travel far through buildings 
• Short-wave radio signals can like long-wave, be received at long distances from the transmitter. That's because they are reflected from the ionosphere - an electrically charges layer in the Earth's upper atmosphere 
• Medium-wave signals can also reflect from the ionosphere, depending on the atmospheric conditions and time of day 

Microwaves are used for satellite communication and mobile phones 

• Communications to and from satellites uses microwaves. But you need to use microwaves that can easily pass through the Earth's watery atmosphere
• For satellite TV, the signal from a transmitter is transmitted into space where it's picked up by the satellite's receiver dish orbiting thousand of kilometres above the Earth. The satellite transmits the signal back to Earth in a different direction where it's received by a satellite dish on the ground 
• Mobile phone calls travel as microwaves between your phone and the nearest transmitter 
• Microwaves are used by remote-sensing satellites to see through the clouds and monitor oil spills, track the movement of icebergs etc.  

Infrared waves are used in remote controls and optical fibres 

• Infrared waves are used in lots of wireless remote controllers 
• Remote controls work by emitting different patterns of infrared waves to send different commands to an appliance 
• Optical fibres can carry data over long distances very quickly 
• They use both infrared waves and visible light 
• The signal is carried as pulses of light or infrared radiation and is reflected off the sides of a very narrow core from one end of the fibre to another 

Visible light is useful for photography 

• Cameras use a lens to focus visible light onto a light sensitive film or electronic sensor 
• The lens aperture controls how much light enters the camera 
• The shutter speed determines how long the film or sensor is exposed to the light 
• By varying the aperture ans shutter speed a photographer can capture as much or little light as they want in their photograph 

Sound travels as a wave 

• Sound waves are caused by vibrating objects. These mechanical vibrations are passed through the surrounding medium as a series of compressions. They're a type of longitudinal waves 
• Sometimes the sound will travel through a person's inner ear and reach their eardrum, at which point they will hear the sound 
• Because sound waves are caused by vibrating particles, the denser the medium, the faster the sound travels through it. Sound generally travels faster in solids than liquids and faster in liquids than in gases 
• Sound can't travel in space because it's mostly a vacuum   

Sound waves can reflect and retract 

• Sound waves will be reflected by hard, flat surfaces
• This is easily notices in an empty room, when you put items in that room, it sounds completrly different. This is because the items absorb the sound quickly and stop it echoing around the room. Echoes are just reflected sound waves 
• You hear a delay between the original sound and the echo because the echoes sound waves have to travel further, and so it takes longer to reach your ears 
• Sound waves will also refract as they enter different media. As they enter denser material, they speed up 

The higher the frequency, the higher the pitch 

• High frequency sound waves sound high pitched. Whereas, low frequency sound waves sound low pitched 
• Frequency is the no. of complete vibrations each second. Common units are kHz and MHz 
• High frequency means shorter wavelength. Bigger the amplitude, louder the sound    

The Universe seems to be expanding

• The universe is bigger all the time. All its galaxies seem to be moving away from each other 

Light from other galaxies is red-shifted

• Different chemical elements absorb different frequencies of light
• Each element produces a specific pattern of dark lines at the frequencies that it absorbs in the visible spectrum
• When we look at light from different galaxies, we can see the same patterns but at slightly lower frequencies than they should be - they're shifted towards the red end of the spectrum. This is called red-shift  

The Doppler Effect

• When something that emits waves moves towards you or away from you, the wavelengths and frequencies of the waves seem different compared to when the source of the wave is stationary 
• The frequency of a source moving towards you will seem higher and the wavelength will seem shorter
• The frequency of a source moving away from you will seem lower and its wavelength will seem longer 
• The Doppler effect happens to both longitudinal waves and transverse waves 

The further away the galaxy, the greater the red shift

• Measurements of the red shift suggest that all the galaxies are moving away from us very quickly and it's the same result whichever direction you look in 
• More distant galaxies have greater red-shifts than nearer ones
• This means that more distant galaxies are moving away from us faster than nearer ones 
• This provides evidence that the whole universe is expanding 

• All the matter and energy in the universe must have been compresses into a very small space. The is exploded and started expanding 
• The expansion is still going. We can use the current rate of expansion of the universe to estimate its age. Our best guess is that the universe is 14 billion years old 
• Steady State theory says that the universe has always existed ans it will always do so. It's based on the idea that the universe appears pretty much the same everywhere by suggesting that matter is being created in space as the universe expands 
• The discovery of the cosmic microwave background radiation (CMBR) some years later was strong evidence that the Big Band was the most likeliest of the two theories

•  Scientists have discovered low frequency electromagnetic radiation coming from all parts of the universe
• This radiation is in the microwave part of the spectrum. It's known as the cosmic microwave background radiation
• The Big Bang theory is the only theory that can explain (CMBR)
• After Big Bang, when universe was hot it emitted high frequency radiation. When it cooled and expanded radiation dropped in frequency and known seen as microwave radiation   

• Many astronomers agree there was a Big Bang, some still believe in Steady State. They say evidence points that way
• Big Bang is perfect, not the whole explanation of universe, observations that theory can't explain. Big Bang predicts tat the universe should be slowing down but instead it's speeding up 
• The Big Bang explains the universe's expansion, but there isn't an explanation for why it exploded or what the condition were like before 
• It seems most likely that the Big Band theory will be adapted in some way to account for its weaknesses rather than dumped. It explains so much so well that scientists will need a lot of persuading to drop it altogether