28/05/13The ULTIMATE energy sourceThe ULTIMATE energy sourceThe sun is the ultimate source of all our energy.For example, we often get energy from beef:BEEF comes from COWS,COWS eat GRASS,GRASS gets energy from the sun by PHOTOSYNTHESIS
28/05/13The 9 types of energyThe 9 types of energyType 3 example sourcesHeatKinetic (movement)NuclearSoundLightChemicalElectricalGravitational potentialElastic potentialType 3 example sources
28/05/13Energy changesEnergy changesTo describe an energy change for alight bulb we need to do 3 steps:Electricity Light + heat1) Write down thestarting energy:3) Write downwhat energy typesare given out:2) Draw an arrowWhat are the energy changes for the following…?1) An electric fire2) A rock about to drop3) An arrow about to be fired
28/05/13Conservation of EnergyConservation of EnergyIn any energy change there is ALWAYS some “waste”energy:e.g. a light bulb:Electricity Light + heatIn this example HEAT is wasted – it’s given to thesurroundings. Waste energy is virtually alwaysheat and it’s always given to the surroundings.
28/05/13Heat and TemperatureHeat and TemperatureThis cup of coffee will ____ ____because it is _____ ____ heatenergy into the surroundings.This drink (taken out of thefridge) will _____ ___ because itis _____ ___ heat energy fromthe surroundings.Heat is a type of energy that will flow from a warm areato a colder one. For example…Words to use – giving out,warm up, taking in, cool down
28/05/13Conduction is all about when heat is transferred through a _________.The heat is passed on by ___________ in the molecules. Thesevibrations get BIGGER when the solid has more ENERGY (i.e. when it isbeing __________).Metals are _______ conductors than non-metals. This is because theheat is carried by free ________ that can carry the energy around themetal and give it to other electrons and ions.ConductionConductionWords – vibrations, electrons, solid, heated, better(I suggest putting in a link to animations of heating differentsolids – these are found on www.educationusingpowerpoint.org.ukand click on “animations”.)
28/05/13ConvectionConvectionConvection is all about when a gas or liquid (“fluid”) moves and carries heatwith it. When the fluid is heated it ____________. This means that itwill become less __________ than the colder fluid around it. Because ofthis the warmer fluid will try to “_______” over the colder fluid, and thisis why warm air rises. This is called a convection ___________. This ishow heat reaches us from the ___________ in this room.In CONDUCTION the heat was passed on by VIBRATIONS in aSOLIDIn CONVECTION the heat is passed on by the FLUID expanding, risingand TAKING THE HEAT with itWords to use: expands, radiators, dense, heated, current, float
28/05/13Some questions on convection…Some questions on convection…1) Freezers in supermarkets are often left open to theair. Explain why the food does not melt easily.2) Explain why a hot air balloon rises in the air.3) Explain why an ice cube floating at the top of a drinkwill cool all of the drink.
28/05/13RadiationRadiationWhen you wear a black t-shirt on a hot, sunny day you wouldfeel ______ than if you wore ____. This is because black_______ infrared radiation (i.e. heat) from the sun betterthan white does.I’m very hot!I’m cool!
28/05/13Some examples of radiationSome examples of radiation
28/05/13Some examples of radiationSome examples of radiation
28/05/13Radiation is when heat moves around in electromagnetic _________ likelight does. Any hot object will emit heat radiation – the hotter it is, themore radiation it emits. This type of radiation is called __________, andtoo much of it will cause _________. Dark, matt colours will absorb ANDemit the _____ infra-red radiation, and light, shiny colours will ________it.The main difference with radiation is that conduction and convection couldONLY happen in solids, liquids or gases, whereas radiation will happenthrough an _____ _____. This is just as well, as otherwise we wouldn’t beable to get any heat from the ___.RadiationRadiationWords – sun, reflect, infra-red, waves, most, empty space, sunburnAnything HOT emits HEAT RADIATION – the hotter itis, the more infra red radiation it emits
28/05/13Energy and PowerEnergy and PowerThe POWER RATING of an appliance is simply how muchenergy it uses every second.In other words, 1 Watt = 1 Joule per secondETPE = Energy (in joules)P = Power (in watts)T = Time (in seconds)
28/05/13Some example questionsSome example questions1) What is the power rating of a light bulb that transfers 120joules of energy in 2 seconds?1) What is the power of an electric fire that transfers10,000J of energy in 5 seconds?1) Farhun runs up the stairs in 5 seconds. If he transfers1,000,000J of energy in this time what is his power rating?1) How much energy does a 150W light bulb transfer in a) onesecond, b) one minute?
28/05/13Calculating the cost of electricityCalculating the cost of electricityClearly, this depends on two things: the POWER RATING ofthe appliance and HOW LONG you leave it on for. Electricityis measured in “units”, also called “kilowatt hours” (kWh).To work out how much something would cost use two steps:1) Find out how many units have been used:No. of units = Power rating x Time appliance is on forin kWh in kW in hours2) Multiply the number of units by how much each one costs:Cost of electricity = no. of units used x cost of each unitin cents in kWh in cents
28/05/13Gravitational Potential EnergyGravitational Potential EnergyTo work out how much gravitational potential energy(GPE) an object gains when it is lifted up we would usethe simple equation…GPE = Weight x Change in height(Joules) (newtons) (metres)GPE∆HW
28/05/13Some example questions…Some example questions…How much gravitational potential energy have the following objectsgained?:1. A brick that weighs 10N lifted to the top of a house (10m),2. A 10,000N car lifted by a ramp up to a height of 2m,3. A 700N person lifted up 50m by a ski lift.How much GPE have the following objects lost?:1. A 2N football dropping out of the air after being kicked up 30m,2. A 0.5N egg falling 10m out of a bird nest,3. A 10,000N car falling off its 2m ramp.4. Mr Richards when bungi-jumping off a 110-metre high bridge inZambia in August
28/05/13EfficiencyEfficiencyEfficiency is a measure of how much USEFUL energy youget out of an object from the energy you put INTO it.Efficiency = Useful energy given out by the deviceEnergy put into ite.g. if 2000 joules of electrical energy are put into akettle and 500 joules of heat energy are gained from it,its efficiency is 500/2000 x 100% = 25%x100%
28/05/13Some examples of efficiency…Some examples of efficiency…1) 5000J of electrical energy are put into a motor. Themotor converts this into 100J of movement energy.How efficient is it?2) A laptop can convert 400J of electrical energy into240J of light and sound. What is its efficiency?Where does the rest of the energy go?3) A steam engine is 50% efficient. If it delivers20,000J of movement energy how much chemicalenergy was put into it?
28/05/13Energy Transfer diagramsEnergy Transfer diagramsConsider a light bulb. Let’s say that the bulb runs on 100watts (100 joules per second) and transfers 20 joules persecond into light and the rest into heat. Draw this as adiagram:100 J/selectricalenergy“Input” energy “Output” energy80 J/s heatenergy (given tothe surroundings)20 J/slight energy
28/05/13Example questionsExample questionsConsider a kettle:1) Work out each energy value.2) What is the kettle’sefficiency?SoundenergyWastedheatHeat towater2000 J/selectricalenergyConsider a computer:150 J/selectricalenergy10 J/swastedsound20 J/swastedheatUsefullight andsound1) How much energy is convertedinto useful energy?2) What is the computer’sefficiency?
28/05/13Renewable vs. non-renewable fuelsRenewable vs. non-renewable fuelsA ________ energy source is blatantly one that can be_______ (“renew = make again”), e.g. _____, solar poweretc.A ___________ energy source is one that when it hasbeen used it is gone forever. The main examples are____, oil and gas (which are called ______ ____, as theyare made from fossils), and nuclear fuel.Words – non-renewable, coal, renewable,fossil fuels, wood, renewed
28/05/13PollutionPollutionWhen a fuel is burned the two main waste products are_____ dioxide and ________ dioxide.Carbon dioxide destroys the ____ layer and helps tocause the _______ ______.Sulphur dioxide, when dissolved in ________, causes______ _____.Words – sulphur, ozone, carbon, acid rain,greenhouse effect, rainwater
28/05/13What doesWhat doeseach part do?each part do?The boiler is where the fuel is burnt to boilwaterThe steam from the boiler is used to turn aturbineThe turbine is connected to the generator,which acts like a dynamo – it generateselectricity out of movementThe steam is cooled down and turned backinto water in the cooling tower
28/05/13Nuclear power stationsNuclear power stationsThese work in a similar way to normal power stations:The main difference is that the nuclear fuel is NOTburnt – it is used to boil water in a “heat exchanger”
28/05/13Advantages of non-renewable fuelsAdvantages of non-renewable fuelsCoal, oiland gasNuclearRelativelycheapReliableFlexible inmeetingdemandRelativelyeasy to findCheap fuelcostsDon’t produceas muchpollution
28/05/13The problems…The problems…Power stations using coal, oil, gas or nuclear fuels can certainlywhack out the energy, BUT…Problem 1 – Fossil fuels and nuclear sources will RUN OUTProblem 2 – Burning fossil fuels will pollute the atmosphereProblem 3 - Nuclear plants run the risk of contamination and thecost of shutting them down (“decommissioning”) isvery highSo what’s the solution?
28/05/13Other ways of generating electricity…Other ways of generating electricity…Can we drive the turbine DIRECTLY?
28/05/13Other ways of generating electricity…Other ways of generating electricity…WindTidalWaveHydro-electric
28/05/13What are the disadvantages of theseWhat are the disadvantages of theserenewable forms of energy?renewable forms of energy?Source DisadvantagesWindWaveTidalHydroelectric
28/05/13Source DisadvantagesWindDepends on weather, visual pollution,difficult to “store”WaveHarms wildlife, depends on size ofwaves, depends on weatherTidalDepends on size of tides, harmswildlife, visual pollutionHydroelectricHabitats can be destroyed, only good asa “short term” supplyAlso, these sources all have high setting up costs
28/05/13Other options…Other options…Geothermal energy – water is heatedusing heat given off by _________rocks underneath the surface of theEarthSolar energy – using solar panels______ can be converted straightinto electricityAlthough renewable fuels are ____, the energy we get from them is“_______”. This means that we have to spend a lot of money ongenerators to make them worthwhile.Words – dilute, radioactive, free, satellites, light