Presentation on theme: "11/10/2015Energy W Richards The Weald School. 11/10/2015 The ULTIMATE energy source The sun is the ultimate source of all our energy. For example, we."— Presentation transcript:
11/10/2015 The ULTIMATE energy source The 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
11/10/2015 The 9 types of energy Type3 example sources Heat Kinetic (movement) Nuclear Sound Light Chemical Electrical Gravitational potential Elastic potential Type3 example sources
11/10/2015 Energy changes To describe an energy change for a light bulb we need to do 3 steps: Electricity Light + heat 1) Write down the starting energy: 3) Write down what energy types are given out: 2) Draw an arrow What are the energy changes for the following…? 1)An electric fire 2)A rock about to drop 3)An arrow about to be fired
11/10/2015 Conservation of Energy In any energy change there is ALWAYS some “waste” energy: e.g. a light bulb: ElectricityLight + heat In this example HEAT is wasted – it’s given to the surroundings. Waste energy is virtually always heat and it’s always given to the surroundings.
11/10/2015 Heat and Temperature This cup of coffee will ____ ____ because it is _____ ____ heat energy into the surroundings. This drink (taken out of the fridge) will _____ ___ because it is _____ ___ heat energy from the surroundings. Heat is a type of energy that will flow from a warm area to a colder one. For example… Words to use – giving out, warm up, taking in, cool down
11/10/2015 Conduction is all about when heat is transferred through a _________. The heat is passed on by ___________ in the molecules. These vibrations get BIGGER when the solid has more ENERGY (i.e. when it is being __________). Metals are _______ conductors than non-metals. This is because the heat is carried by free ________ that can carry the energy around the metal and give it to other electrons and ions.Conduction Words – vibrations, electrons, solid, heated, better View Animation
11/10/2015Convection Convection is all about when a gas or liquid (“fluid”) moves and carries heat with it. When the fluid is heated it ____________. This means that it will become less __________ than the colder fluid around it. Because of this the warmer fluid will try to “_______” over the colder fluid, and this is why warm air rises. This is called a convection ___________. This is how heat reaches us from the ___________ in this room. In CONDUCTION the heat was passed on by VIBRATIONS in a SOLID In CONVECTION the heat is passed on by the FLUID expanding, rising and TAKING THE HEAT with it Words to use: expands, radiators, dense, heated, current, float
11/10/2015 Some questions on convection… 1)Freezers in supermarkets are often left open to the air. 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 drink will cool all of the drink.
11/10/2015Radiation When you wear a black t-shirt on a hot, sunny day you would feel ______ than if you wore ____. This is because black _______ infrared radiation (i.e. heat) from the sun better than white does. I’m very hot! I’m cool!
11/10/2015 Radiation is when heat moves around in electromagnetic _________ like light does. Any hot object will emit heat radiation – the hotter it is, the more radiation it emits. This type of radiation is called __________, and too much of it will cause _________. Dark, matt colours will absorb AND emit the _____ infra-red radiation, and light, shiny colours will ________ it. The main difference with radiation is that conduction and convection could ONLY happen in solids, liquids or gases, whereas radiation will happen through an _____ _____. This is just as well, as otherwise we wouldn’t be able to get any heat from the ___.Radiation Words – sun, reflect, infra-red, waves, most, empty space, sunburn Anything HOT emits HEAT RADIATION – the hotter it is, the more infra red radiation it emits
11/10/2015 Energy and Power The POWER RATING of an appliance is simply how much energy it uses every second. In other words, 1 Watt = 1 Joule per second E TP E = Energy (in joules) P = Power (in watts) T = Time (in seconds)
11/10/2015 Some example questions 1)What is the power rating of a light bulb that transfers 120 joules of energy in 2 seconds? 2)What is the power of an electric fire that transfers 10,000J of energy in 5 seconds? 3)Farhun runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating? 4)How much energy does a 150W light bulb transfer in a) one second, b) one minute? 5)Shaun’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a physics lesson? 6)Damien’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?
11/10/2015 Calculating the cost of electricity Clearly, this depends on two things: the POWER RATING of the appliance and HOW LONG you leave it on for. Electricity is 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 for in kWh in kWin hours 2) Multiply the number of units by how much each one costs: Cost of electricity = no. of units used x cost of each unit in pencein kWhin pence
11/10/2015 Gravitational Potential Energy To work out how much gravitational potential energy (GPE) an object gains when it is lifted up we would use the simple equation… GPE = Weight x Change in height (Joules) (newtons) (metres) GPE HH W
11/10/2015 Some example questions… How much gravitational potential energy have the following objects gained?: 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 in Zambia in August
11/10/2015Efficiency Efficiency is a measure of how much USEFUL energy you get out of an object from the energy you put INTO it. Efficiency = Useful energy given out by the device Energy put into it e.g. if 2000 joules of electrical energy are put into a kettle and 500 joules of heat energy are gained from it, its efficiency is 500/2000 x 100% = 25% x100%
11/10/2015 Some examples of efficiency… 1)5000J of electrical energy are put into a motor. The motor converts this into 100J of movement energy. How efficient is it? 2)A laptop can convert 400J of electrical energy into 240J 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 delivers 20,000J of movement energy how much chemical energy was put into it?
11/10/2015 Energy Transfer diagrams Consider a light bulb. Let’s say that the bulb runs on 100 watts (100 joules per second) and transfers 20 joules per second into light and the rest into heat. Draw this as a diagram: 100 J/s electrical energy “Input” energy“Output” energy 80 J/s heat energy (given to the surroundings) 20 J/s light energy
11/10/2015 Example questions Consider a computer: 150 J/s electrical energy 10 J/s wasted sound 20 J/s wasted heat Useful light and sound 1)How much energy is converted into useful energy? 2)What is the computer’s efficiency?
11/10/2015 Renewable vs. non-renewable fuels A ________ energy source is blatantly one that can be _______ (“renew = make again”), e.g. _____, solar power etc. A ___________ energy source is one that when it has been used it is gone forever. The main examples are ____, oil and gas (which are called ______ ____, as they are made from fossils), and nuclear fuel. Words – non-renewable, coal, renewable, fossil fuels, wood, renewed
11/10/2015 Using non-renewable fuels in power stations 1) A fossil fuel is burned in the boiler 2) Water turns to steam and the steam drives a turbine 3) The turbine turns a generator 4) The output of the generator is connected to a transformer 5) The steam is cooled down in a cooling tower and reused
11/10/2015Pollution When a fuel is burned the two main waste products are _____ dioxide and ________ dioxide. Carbon dioxide is a _________ ___ and helps cause _______ _________. This is produced when any fossil fuels are burned. Sulphur dioxide, when dissolved in ________, causes ______ _____. This is mainly a problem for ___ power stations. Nuclear power stations do not produce these pollutants because they don’t ____ fossil fuels. Words – sulphur, coal, global warming, carbon, acid rain, greenhouse gas, rainwater, burn
11/10/2015 Nuclear power stations These work in a similar way to normal power stations: The main difference is that the nuclear fuel is NOT burnt – it is used to boil water in a “heat exchanger”
11/10/2015 Start up times Different power stations have different start up times: Gas Oil Coal Nuclear Quick Slow
11/10/2015 Advantages of non-renewable fuels Coal, oil and gas Nuclear Relatively cheap Reliable Flexible in meeting demand Relatively easy to find Cheap fuel costs Don’t produce as much pollution
11/10/2015 The problems… Power stations using coal, oil, gas or nuclear fuels can certainly whack out the energy, BUT… Problem 1 – Fossil fuels and nuclear sources will RUN OUT Problem 2 –Burning fossil fuels will pollute the atmosphere Problem 3 -Nuclear plants run the risk of contamination and the cost of shutting them down (“decommissioning”) is very high So what’s the solution?
11/10/2015 Non-renewable energy sources Coal, oil, gas and nuclear AdvantagesDisadvantages Cheap fuel costs Short start-up time for gas and oil Good for “basic demand” Fuel will run out Costs a lot of money to decommission a nuclear plant Pollution – CO 2 leads to global warming and SO 2 leads to acid rain Reliable Nuclear produces little pollution
11/10/2015 Other ways of generating electricity Can we drive the turbine directly without burning any fossil fuels?
11/10/2015 Renewable energy sources summary Wind, tidal, hydroelectric and solar AdvantagesDisadvantages Zero fuel costs Hydroelectric is good for a “sudden” demand Don’t produce pollution Tidal barrages destroy the habitats of wading birds and hydroelectric schemes involve flooding farmland Unreliable (except for hydroelectric) Expensive to build Solar is good for remote locations (e.g. satellites)
11/10/2015 Other renewable options… Geothermal energy – water is heated using heat given off by _________ rocks underneath the surface of the Earth Although renewable fuels are ____, the energy we get from them is “_______”. This means that we have to spend a lot of money on generators to make them worthwhile. This is why solar panels are only used in small things (like calculators) or extremely remote locations (like ____________). Words – dilute, radioactive, free, satellites, light Solar energy – using solar panels ______ can be converted straight into electricity
11/10/2015 Matching supply and demand… “Baseline” power stations Hydroelectric power station might “kick in” here