Year 9 Science (9SPH) Climate Science and Energy Production PDF

Year 9 Science (9SPH) Climate Science and Energy Production Name: TEACHER SOLUTIONS Teacher: 1 | Page ...

Year 9 Science (9SPH) Climate Science and Energy Production Name: TEACHER SOLUTIONS Teacher: 1 | Page  Aug 2024 Introduction 3 Topic information.......................................................................................................................................................................................... 3 Revision Techniques..................................................................................................................................................................................... 5 Chapter 1 – Climate Science 7 1.1 What is the greenhouse effect and enhanced greenhouse effect?............................................................................7 1.2 Observed effects of the enhanced greenhouse effect and climate change................................................................. 14 1.3 Humans can impact climate change – taking action to reduce effects.........................................................................26 Chapter 2 – Electricity 37 2.1 Static Electricity.................................................................................................................................................................................. 37 2.2 Electrical Circuits................................................................................................................................................................................41 2.3 Electrical Power.................................................................................................................................................................................. 57 Chapter 3 – Magnetism 58 3.1 Magnetic Fields....................................................................................................................................................................................58 3.2 Electromagnetism...............................................................................................................................................................................64 3.3 Electric Motors.....................................................................................................................................................................................65 2 | Page Topic information Learning Intentions and Success Criteria Learning Success Criteria Success Criteria Intention (Knowledge/understand): (Skills/explore): Apply, Analyse, Evaluate (Objective) Recall, Understand (1) To understand (1) Understand the energy balance the causes of between incoming and outgoing greenhouse radiation. effect (0.5 (2) Understand the role of greenhouse week) gases in moderating temperature across night and day. (3) Understand the link between infrared radiation and greenhouse gases. (4) Understand the role of excess carbon dioxide and other greenhouse gases in disrupting energy balance and increasing overall surface temperatures. (2) To understand (1) Recall list of climate change (2) Explain effects of rising sea levels the impacts of impacts, including: rising sea (3) Evaluate impact on human, animal, physical climate change levels, increased severe weather geography (0.5 week) patterns, changes to habitats and agriculture, ocean acidification. (3) Human activity (1) Understand the current modes of (3) Evaluate the suitability of renewable energy sources in addressing electricity production and classify to various locations. the effects of as renewable or non-renewable. (4) Explore factors affecting the power output of wind climate change (2) Understand production of turbines. (1 week) electricity using renewable sources including wind turbines. (4) Explain how (1) Understand the basic principle of (6) Calculate overall resistance of basic series and energy moves circuits in terms of moving charge. parallel circuits, using V = IR through electric (2) Understand voltage, current and (7) Analyse current and voltage in basic circuits to circuits resistance and their relationship, theoretical values. (2 weeks) using V = IR (8) Apply understanding of power in circuits (wind (3) Understand the arrangement of turbine and solar panel kits), using P = VI. series and parallel circuits. (4) Understand how voltage and current are measure in circuits using analogue and digital meters. (5) Recall how power is calculated, using P = VI (5) Principles of (1) Understand the shape and (4) Recall the shape and properties of a magnetic field magnetism properties of a magnetic field around a permanent magnet (1 week) around a permanent magnet (5) Apply the right-hand grip rule for magnetic field (2) Understand the relationship around a current carrying wire to single wires and between current and magnetic solenoids field (qualitative only) (3) Understand the principle of a solenoid 3 | Page  (6) Understand the (1) Understand the interaction (5) Apply the right-hand slap rule for the interaction of relationship between external magnetic field and a magnetic field and current carrying wire (single between current carrying wires wire and motors). Extension: motors & magnetism and commutators. electricity) (6) Understand the basic components of a generator (1 week) (conducting coil moving in a magnetic field to generate current). Summative Assessment: Nichrome Wire Investigation– [Green (Data Collection, Analysis, Conclusion), Blue (Evaluation)] (S1 only) Media Analysis Task (S2 only) Ohm’s Law Prac. Unit Test Formative Assessment: Group Practical Report – Wind Turbine Optimisation PhET circuit builder DEEDS revision quizzes 4 | Page Passive revision techniques ☹ allow you to recognise ideas and information but not recall them for assessments. Be aware that the following are passive revision techniques that only aid in increasing your recognition of information. Check that you aren’t doing them! Reading through your notes, your past assessments and key texts. If you are not doing anything with the material, then this is not very helpful for remembering what you read. Typing out all your notes. This can seem very useful as you are keeping busy, but it is mostly a waste of time since it it does not require much brain activity or engagement. Highlighting information in texts. It can be very easy to mindlessly over-highlight most of a document, but unless you do something with the highlights, you are relying on having the text in front of you. Active revision techniques 😊 require you to engage your brain and make it work by doing something with the information you have. You are far mor likely to recall information rather than just recognise it. Some techniques to try are. 1. Flashcards Flashcards allow you to practise summarising information and can help you identify any gaps in your learning. You can use them in a variety of different ways: - Condense notes about a specific topic on to a card. - Write a term on one side and a definition the other. - Write a question on one side and the answer on the other. Example image of flash cards and student sample The most important use of flashcards is to test yourself! Don’t just read them, actively hide the answers so you are practising recall. Ask your friends and family to test you. Include colours and images to improve your memory, but don’t spend more time making them pretty than testing your recall of the information. There are also lots of apps available to create flashcards. 2. Sticky notes Sticky notes are good for summarising information and remembering key details. Use colours to identify themes and stick them around your home - but move them regularly so you don't get used to having them in a specific place. 3. Practice questions If you can access past test or deeds quizzes, working through these is a great way to test your knowledge, either by writing plans or full answers, First, try answering the questions without looking at your notes, to get an idea of which areas need more work. Then, with your notes, practise planning the framework for your answers. Use lists to compare points for and against a statement. Finally, come back and answer the question again without your notes. 5 | Page  4. Study Groups Revising as a group can give you an opportunity to quiz and test each other. Have a go at explaining topics to others without referring to your notes. It’s a great way to aid your own memory and understanding. 5. Mind Maps Mind maps can be a great way to identify connections between ideas. Use colours and images, which will aid your memory. You may find drawing diagrams useful to remember processes or cycles. However, do not just create a mind-map from your notes and look at it. Do something with it. Test what you can remember from the mindmap. Can you recreate it without looking at it? Can you summarise the concepts even further to help you memorise them? Can you add remember examples for each of the nodes? 6. Spread out your tests Test yourself on the same material at the end of the day, the next day and at the end of the week. Change the order of what you test yourself on so that you don’t get used to the same pattern. Top Revision Tips! 1. “The best time to start revising is day 2 of your topic. The second best time to start revising is now.” Start your revision as early as possible. Plan your revision timetable this evening and get going! You will feel the benefits once the assessments start. Remember to start on the topics that you are least confident about, and dedicate more time to them overall. 2. The most important concept in revision is active vs passive revision. Active revision means doing something with the information you need to learn (usually testing your memory). Passive revision techniques include simply reading through your old notes. Don’t fall into to the trap of thinking that this is enough! See above for active revision ideas. 3. Revising can be hard work, so break up your revision sessions into chunks. A good starting point is 20 minutes, followed by a 10-minute break away from your studies. But make sure you return to revising after the break! 4. Make sure that you vary your methods of revision. Making endless flashcards can be disheartening and overwhelming. Differ the material you revise from the difficult to the more familiar. This makes it more interesting, and small chunks are easier to remember. 5. Test, test, test yourself. Start each day trying to remember 10 facts you learnt from the day before. Test yourself on what you have learnt at the end of the day, the next day and at the end of the week. Change the order of what you test yourself on so that you don’t get used to the same pattern. 6. Review your revision plan at the end of each week. Did you do enough? Did you remember more this week than last week? What time of day do you revise the best? How can you improve your revision for next week? 7. Don’t spend all your time revising. Build some flexibility into your plan so you can enjoy some breaks. Self-care is important – get enough sleep, eat well and keep hydrated. 6 | Page 1.1 What is the greenhouse effect and enhanced greenhouse effect? Energy Balance and Radiation The earth maintains an energy balance between incoming solar radiation and outgoing radiation back into space. However, not all radiation is the same. Energy comes from the sun as a mix of “short-wave” radiation (UV, Visible) and “long-wave” radiation (Infrared heat) To maintain the overall balance of energy, the earth emits “long-wave” (______INFRARED____) back into space. ULTRAVIOLET is the electromagnetic radiation that can burn our skin. VISIBLE LIGHT_ (ROYGBV) is seen by our eyes. INFRARED is felt as heat. Gases in the Earth’s Atmosphere Earth’s atmosphere is almost exclusively made up of nitrogen (N2) and oxygen (O2) _______99____ % Living organisms require _____OXYGEN_____________ for respiration and _______NITROGEN_______________ is crucial for plant growth. Nitrogen and oxygen have _NO____ effect on the radiation entering the atmosphere from the Sun or the radiation emitted from the Earth’s surface. Of the remaining ~ 1%, some act as Greenhouse Gases. Carbon dioxide and other gases with _______THREE OR MORE___________________ atoms in each molecule behave differently. These are known as Greenhouse Gases (GHG). GHG allow ____SHORT_____-wave radiation to pass through, but can absorb and re-emit ___LONG________-wave IR radiation. 7 | Page  Water vapour (H2O) can also act as a greenhouse gas. Complete the table below, indicating the formula and whether or not they are a greenhouse gas (GHG). Gas % Formula GHG? Nitrogen 78.1% N2 No Oxygen 20.9% O2 No Argon 0.9% Ar No Carbon Dioxide 0.04% CO2 Yes Neon 0.002% Ne No Helium 0.0005% He2 No Methane 0.0002% CH4 Yes The Greenhouse Effect Horticulturalists & gardeners have long understood the benefits of a greenhouse. The glass of the greenhouse traps some infrared radiation, keeping plants warmer during cold conditions. Seeds germinate and seedlings survive more readily. 8 | Page  In a similar way, the greenhouse gases in the Earth’s atmosphere keep the Earth’s temperature from becoming too cold at night. GHG absorb and re-emit some IR radiation back to the Earth’s surface, keeping us warm. Without this effect, Earth’s temperature would be about -18 oC rather than 15 oC. 9 | Page The Enhanced Greenhouse Effect Due to increased levels of greenhouse gases in the atmosphere, Earth has been experiencing an Enhanced Greenhouse Effect. Label the diagram below and complete the table, describing the key steps: Step Description 1 Solar radiation reaches the Earth's atmosphere - some of this is reflected back into space. 2 The rest of the sun's energy is absorbed by the land and the oceans, heating the Earth. 3 Heat radiates from Earth towards space. Some of this radiative heat is trapped by greenhouse gases in the atmosphere, keeping the Earth 4 warm enough to sustain life. Human activities such as burning fossil fuels, agriculture and land clearing are increasing the 5 amount of greenhouse gases released into the atmosphere. 6 This is trapping extra heat, and causing the Earth's temperature to rise, along with other effects. Enhanced Greenhouse Effect Simulator 10 | Page Use the PhET simulator and answer the questions below. Site: https://phet.colorado.edu/sims/html/greenhouse-effect/latest/greenhouse-effect_all.html or https://bit.ly/PhETEnhancedGreenhouseEffect Settings: Select wave mode on the initial screen Show Energy balance Leave clouds on Questions Questions 1. How has the amount of GHG changed since the last Ice Age? The concentration has increased 2. As the amount of GHG increases, describe the effect on the INCOMING solar radiation (yellow). There is NO effect – solar radiation remains constant. 3. As the amount of GHG increases, describe the effect on the mix of OUTGOING and REFLECTED solar radiation (red). The intensity of the emitted radiation increases. A greater proportion is reflected by GHG back to the surface. Total outgoing radiation remains constant (as per Energy Balance graph) 4. As the amount of GHG increases, describe the effect on the overall surface temperature. Surface temperature increases. 5. As the amount of GHG increases, describe the effect on the Energy Balance. There is an initial drop in the Outgoing radiation as the atmosphere adjusts and the surface temperature increases gradually, then the Net Energy Balance returns to zero. After a short time, the Incoming = Outgoing. 11 | Page  Section 1.1: Key Summary Questions 1. What are the key types of radiation in solar energy? In order of increasing wavelength: UV, Visible, Infrared. 2. Describe the difference between long-wave and short-wave radiation. Wavelength. Long-wave radiation is more readily absorbed and re-emitted by Greenhouse Gases. Oxygen and Nitrogen are transparent for long and short-wave radiation. 3. What are the most common gases in the Earth’s atmosphere? Oxygen (21%), Nitrogen (78%) 4. What is the difference between the structure of a greenhouse gas (GHG) and non-greenhouse gas? Greenhouse gases have 3 or more atoms per molecule (eg. Carbon-dioxide CO2). 5. What are the key characteristics of a GHG? GHG can absorb long-wave (IR) radiation, but allow short-wave radiation to pass through. 6. How does a garden greenhouse improve the growth of seedlings? 12 | Page  The glass of the greenhouse traps some infrared radiation, keeping plants warmer during cold conditions. 7. What type of radiation is trapped inside the greenhouse? Infrared radiation (long-wave) 8. What would Earth’s climate be like without the Greenhouse Effect? Hotter during the day, colder at night. 9. Compare the total amount of incoming solar radiation to that emitted as long-wave radiation into space. The amounts are the same. 10. What type of radiation is emitted by the Earth’s surface? Infrared radiation. 11. What has been the effect of increasing the amount of greenhouse gases in the Earth’s atmosphere since the last Ice Age? Increased surface temperature. 13 | Page 1.2 Observed effects of the enhanced greenhouse effect and climate change The Enhanced Greenhouse Effect has led to a range of climate and environmental changes, many of which have been too rapid for species (including humans) to adapt. Complete the diagram below, indicating increase ( ↑ ), decrease ( ↓ ) or changing ( ↺ ) Media Research Task Task a) Go to https://www.dcceew.gov.au/climate-change/policy/climate-science/understanding-climate-change#oc ean-warming-and-sea-level-rise OR: https://bit.ly/DCCEWClimateScience b) Summarise one of the four sections in ~ 200 words, addressing the following key points: a. What evidence is there for this observed effect? b. How is the data gathered? c. Why is this effect important for our city/country? c) Report back to the class with your findings. Class Discussion 14 | Page 15 | Page The Carbon Cycle To help understand the effects of increased CO2 emissions, we need to understand the carbon cycle. This describes how carbon moves between the atmosphere, soils, living creatures, the ocean, and human sources. The atmosphere only makes up 1% of the carbon sink, so small changes in CO2 make a large difference to greenhouse effect. Carbon Cycle Stage Description / Equation Auto and Factory Emissions When burned to release energy, carbon is released as carbon dioxide: (burning fossil fuels) 𝐶 + 𝑂2 → 𝐶𝑂2 Photosynthesis Plants convert carbon dioxide and water to oxygen and glucose (food for their own growth) 6𝐶𝑂2 + 6𝐻2𝑂→6𝑂2 + 𝐶6𝐻12𝑂6 Dead organisms to fossil Over thousands of years, fossilised plant and animal matter is converted to coal, and fossil fuels oil and natural gas under the oceans and land, capturing carbon. Plant and animal Animals and plants respire, converting oxygen and glucose to water and carbon respiration dioxide to obtain energy. 6𝑂2 + 𝐶6𝐻12𝑂6→6𝐶𝑂 + 6𝐻2𝑂 2 Decay organisms Carbon dioxide is released by bacteria and micro-organisms as dead plant and animal matter decays. 16 | Page  Ocean Uptake Carbon dioxide is dissolved into lakes and oceans. Experiment: The Carbon Cycle Aim: To investigate how carbon cycles during the burning of organic matter. Equipment: The equipment setup is shown in the diagram below. TASK: Label the following parts: clamp, Bunsen burner, rubber stopper, test tube, retort stand, glass tube. Method 1. Gather some mulch, small leaves and bark (organic matter). 2. Put the organic matter into a test tube. 3. Close off the test tube using a rubber cork with a tapered glass rod inserted inside. 4. Carefully weigh the test tube and mulch. 5. Using a Bunsen Burner, strongly heat the bottom of the test tube containing the organic matter. Apply the flame 10 cm below the test tube for a duration of 2 mins. 6. Turn off the Bunsen burner, allow the tube to cool and examine the remains. 7. Weigh the test tube and remains. Method 1. Mass of mulch and test tube before heating: ______________________________ g 2. Mass of mulch and test tube after heating: ______________________________ g 3. Change in mass: ∆𝑚 = ___________________________ g ∆𝑚 4. Calculate the percentage mass lost: % 𝑚𝑎𝑠𝑠 𝑙𝑜𝑠𝑡 = 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑚𝑎𝑠𝑠 ×100% = _______________________ g 17 | Page Questions 1. Which elements is the organic matter (biomass) made up of? Carbon, Hydrogen, Oxygen, Nitrogen 2. List the major gases emitted. Carbon dioxide, water vapour 3. Did the biomass produce pollution? What evidence do we have of this? Yes – Carbon dioxide, water vapour, oils. Oils stain the inside of the glass 4. What evidence is there of a chemical change taking place? Permanent colour change. 18 | Page Human behaviour influences the carbon cycle in a number of ways, notably deforestation and increased consumption of fossil fuels. Fossil Fuels As mentioned in the Carbon Cycle summary, the industrial revolution has led to a dramatic increase in the volume of fossil fuels used by human civilization. When coal (carbon in solid form) is burned to release energy, carbon is released as carbon dioxide: Carbon + Oxygen → Carbon dioxide. 𝐶 + 𝑂2 → 𝐶𝑂2. Similarly other fossil fuel sources such as methane also release carbon dioxide when burned. Methane + Oxygen → Carbon dioxide + Water 𝐶𝐻4 + 𝑂 → 𝐶𝑂2 + 2𝐻2𝑂. 2 Deforestation Plants act as a “sink” for carbon through photosynthesis. They convert carbon dioxide and water to oxygen and glucose (food for their own growth). 6𝐶𝑂2 + 6𝐻2𝑂→6𝑂2 + 𝐶6𝐻12𝑂6 As humans have cleared large amounts of __________NATURAL FORESTS____________ for large scale _________AGRICULTURE and CITIES___________________, the net amount of carbon dioxide captured by plants has ___DECREASED________, leading to ___MORE_________ CO2 in the atmosphere. 19 | Page Oceans – Carbon Sink, Increased Acidification & ocean warming. Earth’s oceans are the largest sink for carbon (26% of all human emissions) Carbon dioxide dissolves into the oceans and is converted to carbonic acid and carbonates Carbonates are used by shellfish, but increased overall acidity can make it harder for shells to be created. Who and what may be impacted by increased ocean acidity? Increased ocean acidity negatively impacts life forms that rely on carbonate-based shells and skeletons, organisms sensitive to acidity organisms higher up the food chain that feed on these sensitive organisms communities dependent upon these organisms (fishing etc.) Organisms may adapt, but changes are happening very fast… Warmer oceans are also problematic as this reduces the amount of carbon dioxide that can be absorbed. Who and what may be impacted by increased ocean temperatures? Increased temperature reduces the solubility of carbon dioxide in ocean water. More carbon dioxide in the atmosphere leads to further greenhouse effect, which increases temperature. Increased temperature further reduces solubility. This is known as a positive feedback loop. 20 | Page Video Activity – Human Impact on Earth’s Climate https://clickv.ie/w/3Hgy (How Earth Made Us: The Human Planet (56 mins). Answer the following questions as you watch the video: 1. For how many years have humans been farming the Earth? 11,000 years 2. Two gases generated by this early farming had a major impact on the Earth’s climate. What were the two gases and what was their impact? Carbon dioxide and methane 3. How long ago did humans first begin to use the mineral ore malachite to make tools? 2000 years 4. How many years ago did humans first begin changing the course of waterways? 5. How long ago did humans begin harnessing the wind? What did they do with this new power source? 500 years. Developed global trade routes. 6. List the Earth’s resources that are utilised in building an aircraft. Mine bauxite to produce aluminium. Mine malachite to produce copper. Perspex from oil. 7. Describe how human activity is affecting the formation of sedimentary rocks. Waste plastic flows from rivers into the ocean where they settle at the bottom. The plastic will eventually form rocks with other sediment. 8. What percentage of the Earth’s ice‐free landscape is altered by human activity? 75% 9. About how long does it take for 2 cm of top soil to form? 500 years 10. How have humans interfered with the water cycle? 21 | Page  Diverted waterways for farming and drinking water. Some water no longer reaches the ocean. The hunt for oil: 11. How much oil do we use each year? Each day? 31 billion a year = 84 million a day = 1000 per second 12. How many years does it take for oil to form? 300 million years 13. Describe what is meant by ‘rock oil’. Oil found in rocks/sand – tar sands 14. What are the problems with exploiting rock oil? Large areas of native habitats need to be cleared. Expensive. 15. Ancient deposits of methane gas caused global warming 55 million years ago. What were the effects of this warming? What scientific evidence do we have of this? High global temperatures. Tropical climate in the artic. Fossilised evidence of ancient trees found in arctic rock. 16. Describe how the creation of the Himalayas affected ancient global warming. Weathering. Carbon dioxide reacts with minerals in the rock which dissolves in water and travels to the ocean where it is used by microscopic organisms. This reduces CO2 in the atmosphere, cooling the climate. 17. What trials are humans undertaking to try to remove excess carbon from the atmosphere? Remove CO2 from the atmosphere with artificial trees. Induce large algal blooms. 18. What is the purpose of the storage facility at Svalbard? Why is this storage facility necessary? Preserve global food sources from disasters. The planets future and human food security is at risk due to climate change and other factors. 22 | Page Section 1.2 Key Summary Questions 1. List 4 key impacts of the enhanced greenhouse effect that we have observed in Australia? Australia’s changing climate – increased overall temperatures Ocean warming and sea level rise Extreme weather events Altered rainfall patterns 2. What is the carbon cycle? The carbon cycle describes how carbon moves between the atmosphere, soils, living creatures, the ocean, and human sources. 3. For each stage of the carbon cycle, indicate whether carbon is captured or released into the atmosphere. Carbon Cycle Stage Capture / Release of carbon dioxide Auto and Factory Emissions (burning fossil Release fuels) Photosynthesis Capture Dead organisms to fossil and fossil fuels Capture Plant and animal respiration Release Decay organisms Release Ocean Uptake Capture 23 | Page  4. Write the Word and Chemical Equation for photosynthesis Carbon dioxide + water → oxygen and glucose 6𝐶𝑂2 + 6𝐻2𝑂→6𝑂2 + 𝐶6𝐻12𝑂6 5. Write the Word and Chemical Equation for animal and plant respiration. oxygen and glucose → carbon dioxide + water 6𝑂2 + 𝐶6𝐻12𝑂6 →6𝐶𝑂2 + 6𝐻2𝑂 6. List five common fossil fuels Coal, natural gas, oil, methane, kerosene, propane, butane, petrol, diesel 7. Write the Word and Chemical Equation for burning of coal. Carbon + Oxygen → Carbon dioxide. 𝐶 + 𝑂2 → 𝐶𝑂2. 8. Explain how ocean warming can be considered as a positive feedback effect. 24 | Page Positive feedback: When one factor in a system is reinforced by another, which then reinforces the first factor. The solubility of carbon dioxide decreases as temperature of water increases. More carbon dioxide remains in atmosphere. Increased enhanced greenhouse effect increases overall temperature of atmosphere and oceans. Further reduction in solubility. 9. THE CARBON CYCLE Annotate this diagram of the carbon cycle to explain what happens during each of the named processes: photosynthesis, cell respiration, fossilisation, combustion, feeding, decomposition. You should explain what compounds the carbon atoms are found in – for example, carbon atoms in carbon dioxide in the air are used to make glucose (C6H12O6) molecules when plants do photosynthesis. 25 | Page 1.3 Humans can impact climate change – taking action to reduce effects There are number of key actions that we can take to reduce the effect of human-induced climate change. Brainstorm list: Reduce Switch to less impactful transport (e.g. walk/ride more often) Eat locally produced food to reduce transport related emissions. Switch to more efficient energy sources (e.g. LEDs) Switch to renewable energy sources (instead of fossil fuels) Re-use Avoid single-use items that use significant energy to produce Avoid landfill Recycle Redirect materials from landfill so they can be recycled (glass, plastic, paper) Plant more trees to reverse effects of deforestation. 26 | Page Identifying Renewable Energy Resources. Renewable energy resources are preferred to fossil fuel sources as they lead to lower overall carbon dioxide emissions. Specifically, a renewable energy resource must satisfy the following criteria: Criteria Details Be replenished by natural processes in a relatively Solar is day/night, compared to fossil fuels – millions short time period of years. Not negatively impact future generations i.e. avoiding plant based fuels that lead to food shortages. Solar Energy Solar power is generated when light is directed onto a solar cell, creating current and voltage through a physical phenomenon called the _______PHOTOELECTRIC EFFECT____________________________. Energy Transformation: 𝐿𝑖𝑔ℎ𝑡 →𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 Characteristic Details Key advantages Ideal for Australia, where solar irradiance is very high. No moving parts – low maintenance costs. Versatile applications – from small to large scale. PV cells produce DC electricity, which can be converted to AC via an inverter for use 27 | Page  or export. Strong uptake at domestic level (rooftop solar). Disadvantages Not suitable for overnight use unless batteries are used. Angle of panels and minimal shading is crucial for efficient operation Interesting? CGS has largest array of any school in Australia. Hydroelectric Power Hydroelectric power involves construction or use of an existing dam. Water flows down through a ____________penstock___________, spinning a ____________turbine______ and generating electricity. Hydroelectric dams are very efficient, but are clearly a large-scale investment that drastically alters the environment. Characteristic Details Key advantages Very efficient. Works very well in regions such as Tasmania – relatively low population, hilly terrain, high rainfall Disadvantages Large-scale, long-term investment – most suitable for large-scale rather than small-scale applications. Alters river flow and displaces communities from flooded valleys Interesting?. 28 | Page Wind Energy Wind power is produced when the blades of the turbines spin, generating electricity in the turbine mounted on top of the shaft. Energy Transformation: 𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 (𝑊𝑖𝑛𝑑) →𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 (𝑇𝑢𝑟𝑏𝑖𝑛𝑒)→𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 Australia has excellent wind resources by world standards. The southern coastline experiences significant wind from the Southern Ocean and many sites have average wind speeds above 8 m s-1 at turbine hub height. Wind accounted for 10 per cent of Australia’s total energy generation in 2021 and more than one-third of renewable energy generated (Source: Department of Climate Change, Energy, the Environment and Water (2022) Australian Energy Statistics). Macarthur Wind Farm in Victoria. 140 turbines, producing 420 MW (220,000 homes, 1.7 MT of CO2 reduced) Characteristic Details Key advantages Ideal for Australia, particular coastal remote areas. Established technology and high power production. Good for large scale use. Disadvantages Some opposition due to aesthetics. Consideration needs to be given to bird populations. Greater maintenance required than solar. Inconsistent production due to variable wind. Less suitable for small scale domestic use. Interesting? 29 | Page Case Study: Wind Turbine Investigation Introduction: One of the most practical sources of renewable energy is wind. It is readily available, especially to coastal areas of Australia and can deliver large amounts of electricity directly to communities. In this practical, you will be investigating some of the key parameters associated with wind turbines. Whilst the specific values may not always be applicable to large scale turbines, the scientific approach and methodology is very relevant to this unit. Key questions to consider: 1. What is the relationship between the angle of the blades on the wind turbine and the electrical power it delivers? 2. What blade area on the wind turbine will deliver the most power? 3. How many blades on the wind turbine will deliver the most power? Part A: Sample Results You will be setting up the circuit containing STELR model wind turbine shown below. The circuit is used to measure the electrical power delivered by the STELR model wind turbine. A fan near the turbine will produce the wind. In the diagram above, trace with a pencil the leads that go from the wind turbine to the lamp on the STELR testing station then to the ammeter (the STELR multimeter on the ammeter setting), and then back to the wind turbine. You can see they form a loop, or circuit. As they are all along the same path that the current flows, they are connected in series with each other. Notice that the voltmeter (the STELR multimeter on the voltmeter setting) is just connected across the lamp on a separate small loop. This means it is 30 | Page parallel with the lamp. The circuit diagram is shown here. Calculations Because the ammeter setting of the multimeter is in milliamp, you will directly calculate the power in milliwatts and will not need to perform any unit conversions. To do this, we adapt the formula, as shown here: P=VxI where P = electrical power, in milliwatts V = voltage, in volts I = current, in milliamps Sample calculation A student set up the circuit to measure current generated by a wind turbine. The wind turbine had 6 blades in the hub. The final steady voltage was found to be 1.72 V and the current was 26.2 mA. What power (in milliwatts) was being delivered by the model wind turbine? Solution: P=VxI where P = electrical power, in milliwatts V = voltage = 1.72 V I = current = 26.2 mA Hence Power = 1.72 x 26.2 = 45.1 mW Procedure SAFETY: First ensure all group members are wearing goggles. Set up your equipment as described below. 1. Make sure the 3 blades are tight in the hub of the turbine and are all at the same angle, in this first case 45o, to the face of the hub (facing the same direction), like those in Figure 3. Use the notches in the hub (22.5 degrees each) to help. Then set up the model wind turbine in the stand, as shown in Figure 1. 2. Make sure that the hub is tight on the motor drive shaft and that you are using the bottom shaft, as shown in Figures 1 and 4, which means the model wind turbine will be ungeared. 31 | Page  3. Connect the circuit as shown 1, with the plugs inserted into the lamp sockets of the STELR testing station. 4. Place the three-speed fan on the bench so that the front of the fan is 50 cm from the front of the hub on the wind turbine, as shown in Figure 4. Do not change the distance between the fan and the turbine over the course of the experiment. 5. Raise or lower the turbine on the retort stand so the centre of the hub of the turbine is at the same height above the bench as the centre of hub of the electric fan. This means the two hubs should be in a direct line with each other, as in Figure 4. 6. Set the ammeter to the 200m setting. (maximum reading of 200 mA.) (See Fig 1) 7. Set the voltmeter to the 20 setting. (maximum reading of 20 V.) 8. When your teacher has given permission, turn the fan on to the highest setting. 9. Once a steady reading is obtained, record the current and voltage in the table below. 10. Turn off the fan and return both the ammeter and voltmeter to the OFF position. Keep the set-up without altering it, ready for part B. Results for Part A (Test run) Current (mA) Voltage (V) Power (mW) Calculations for Part A Calculate the electrical power delivered by the STELR model turbine, in milliwatts. (See the example in the introduction) Part B: Investigating the three key independent variables 1. What is the relationship between the angle of the blades on the wind turbine and the electrical power it delivers? IV1 Angle of blade (degrees) DV Power (mW) CV1 Distance to fan (cm) CV2 Number of blades CV3 Area of blade (cm2) CV4 Air speed (m/s) Procedure Set up your equipment as for Part A. Once connected, check with your teacher before turning on the fan. 1. Discuss among your group members the values of the 6 different angles you will test – these are between 0° (flat against the wind) and 90° (square or perpendicular against the wind). Use the 22.5o notches on the hub to guide you. 2. Attach three red blades, and carefully ensure that the blade angles are the same for each blade 32 | Page 3. Ensure that all your controlled variables are the same across the different angles – the position of the wind turbine in front of the fan, the distance between the fan and the wind turbine, the speed of the wind from the fan, and others. Note these for your method. 4. Collect your data for each of the angle settings you have chosen. Angle Current (mA) Voltage (V) Power (mW) 2. What blade area on the wind turbine will deliver the most power? IV2 Area of blade (cm2) DV Power (mW) CV1 Distance to fan (cm) CV2 Number of blades CV3 Angle of blade (degrees) CV4 Air speed (m/s) Procedure Set up your equipment as for Part A. Once connected, check with your teacher before turning on the fan. 1. In this part of the investigation, you will use the optimum blade angle found for IV1. The optimum blade angle is now a controlled variable. 2. You will now investigate the power produced by the wind turbine for different blade areas (colours). 3. Attach three blades, and carefully ensure that the blade angles are the same for every blade. 4. Ensure that all your controlled variables are the same across each of the “area of blades” run – blade angle, the position of the wind turbine in front of the fan, the distance between the fan and the wind turbine, the speed of the wind from the fan, and others. 5. Collect your data for each of the blade areas. Blade Area Current (mA) Voltage (V) Power (mW) Yellow (15 cm2) Blue (20 cm2) Red (30 cm2) 33 | Page  3. How many blades on the wind turbine will deliver the most power? IV3 Number of blades DV Power (mW) CV1 Distance to fan (cm) CV2 Area of blade (cm2) CV3 Angle of blade (degrees) CV4 Air speed (m/s) Procedure Set up your equipment as for Part A. Once connected, check with your teacher before turning on the fan. 1. In this part of the investigation, you will use the optimum blade angle (IV1) and the optimum blade area (IV2). These are now a controlled variable. 2. You will now investigate the power produced by the wind turbine for different number of blades: from 2 – 12 blades 3. Attach the blades, and carefully ensure that the blade angles are the same for every blade. 4. Ensure that all your controlled variables are the same across each of the “number of blades” run – blade angle, the position of the wind turbine in front of the fan, the distance between the fan and the wind turbine, the speed of the wind from the fan, and others. 5. Collect your data for each of the number of blades. No. of Current (mA) Voltage (V) Power (mW) blades 2 3 4 5 6 7 8 9 10 11 12 34 | Page Part C: Advice for the Wind Turbine Report You are to submit a GROUP report detailing your group’s findings about the most effective design of the STELR wind turbine. Use the shared GDoc Wind Investigation Template to enable effective collaboration. Questioning and predicting – provided. Planning and conducting – provided. Processing and analysing data and information. Present the data that you collected in a table and create appropriate graphs. Make sure you create the correct type of graph for each variable, with Power as dependent each time. If you were unable to get results to work, use the sample results file supplied here: http://bit.ly/STELRWindTurbineData. Evaluating How clear were the results? How could your method be improved next time to avoid errors and achieve more consistent results (if that was even possible). Even if you can’t fix them, it’s better to acknowledge flaws in your method where they exist! Always try to answer the question: “Why has this occurred?” as you discuss results. How did you minimise these errors? What steps can be taken to reduce them? 35 | Page 2.1 Static Electricity Charge is a fundamental property of all matter (like mass) There are two forms of charge in the universe: _____________positive______ and _________negative________ Atoms contain positive charge (_______________protons) and negative charge (___________________electrons) Electrons are generally the most mobile charge carriers When there is an equal number of charges, an object is ____________________neutral. When there is an excess of electrons, an object is _____________________negatively charged. When electrons are removed, an object is _______________________positively charged. Objects can repel or attract depending on their relative charge. Combination of charges Result Positive + Positive Repel Negative + Negative Repel Positive + Negative Attract Static Electricity Demo: Van de Graaff Generator Electrons are easily removed from an atom, leaving an object positively charged. The upper “comb” is connected to a large metal sphere. A belt runs against the comb, removing electrons from it. This makes the whole metal sphere positively charged. 36 | Page Use the Predict-Observe-Explain model for the following scenarios 1. A source of electrons (grounding rod) can lead to an electrical spark from the rod to the large sphere. Prediction Observation Explanation Sphere is positively charged. Source of electrons from grounding rod travels across air gap (seen as spark). 2. A person with long hair stands on a chair (isolated from ground) and keeps their hand on the sphere as the VDGG starts up and charges. Prediction Observation Explanation Sphere is positively charged. A person standing on a chair is isolated from the ground and also becomes positively charged. Individual hairs are positively charged and repel each other – the effect is seen as they are pointing in all directions. 37 | Page  3. A pile of small foil trays is placed on the VDGG sphere, which is then switched on. Prediction Observation Explanation Sphere is positively charged. Foil trays are isolated from the ground and also become positively charged. Individual trays are positively charged and repel each other – the effect is seen as they fly apart from each other. 4. Graphite coated ball on a string (making it insulated from ground) is hung close to the VDGG sphere once it is charged. Prediction Observation Explanation Sphere is positively charged. Neutral ball on a string is initially attracted to the sphere. When contact is made, some electrons jump from the ball to the sphere, making the ball positively charged. The sphere is still positively charged as only a small number of electrons jump across. Ball and sphere now repel each other. 5. Perspex rod rubbed with wool, brought close to a narrow stream of water. Prediction Observation Explanation Initially, both the Perspex and the cloth are neutral because each has an equal amount of positive and negative charges. When rubbed together, the electrons will move from the rod to the cloth, leaving the rod slightly positive. The rod is non-conducting so the charge remains even though it is being held. As the rod is brought near to a thin stream of water, the negative side of the water molecules (O) orients to become attracted to the rod. The stream of water “bends” toward the 38 | Page  rod. Section 2.1: Key Summary Questions 1. What are the two types of charge in an atom and which part of the atom holds each? Positive charge : Proton, Negative charge: Electron 2. If a neutral piece of metal that is isolated from the ground loses electrons, what will its overall charge be? Positive 3. Complete the table below, indicating whether the objects will be attracted or repelled: Electron + Proton Attract Positive sphere + negative sphere Attract Negative charged rod + neutral paper Attract Negatively charged ball + electron Repel 4. Explain why a positively charged plastic ball that makes contact with the ground becomes neutral. Ground is a large source of electrons, which flow onto the plastic ball, making it neutrally charged. 39 | Page 2.2 Electrical Circuits In conducting materials, electrons are free to move and can “flow”. We call this electrical _______________ current ______________. In an historical quirk, we tend to use _____________Conventional Current________________ for circuit analysis. Conventional current moves from + to – (as though it was the protons moving). Electrons flow in the opposite direction. Current is measured in _____________Amperes ______________ (A) and we use the symbol “I ”. Voltage We can think of Voltage as the “pressure” that drives the current around the circuit Voltage is also defined as the amount of energy used across each component (sometimes call ______________Voltage Drop____________) Voltage is measured in ____________ Volts ____________ (V) Resistance For a given supply voltage, the current is determined by the total amount of resistance in a circuit Resistance effectively constricts the current, like reducing the diameter of the pipe carrying water Resistance is measured in _________Ohms_________ (Ω) 40 | Page  Resistance depends on: Material type Length Cross-section Area Materials with low resistance are called __________________________conductors Materials with high resistance are called _________________________insulators 41 | Page PRAC: Resistance of Nichrome Wire Questioning and predicting Background information: This experiment aims to investigate the effect of the length of nichrome wire on its resistance. ρ𝐿 Electrical resistance is known to vary according to the following formula: 𝑅 = 𝐴 , (Lumen, 2023). The formula indicates that there is a linear relationship between length and resistance. Definitions: R = Resistance in Ohms (Ω) L = Length (m) A = Cross-section area (m2) ρ = Resistivity (a property of the material) (Ω m) In this experiment, we will be using Nichrome wire (a nickel-chrome alloy) which has relatively high electrical resistance. Cross section area (A) and Resistivity ( ρ ) remain constant. Research Question: What is the effect of length of nichrome wire on its resistance? Hypothesis: If the length (L) of a sample of nichrome wire is increased, the resistance (R) will increase in a linear ρ𝐿 relationship according to the formula: 𝑅 = 𝐴. Planning and conducting Independent Variable Length (L), in metres. Lengths of 1, 2, 3 & 4 metres were chosen to provide an adequate range of resistance. Dependent Variable Resistance (R), measured in Ohms (Ω) NOTE: Resistance is calculated using Ohm’s Law, measuring Voltage (V) and Current (I) using a digital 𝑉 meters and then using 𝑅 = 𝐼 to calculate the resistance of each sample. Control Variables Resistivity ( ρ ) – the type of wire (Nichrome) remains the same Cross section area (A) – same diameter wire used. Supply voltage – 6 V DC. Measuring circuit – meters, connecting wires are constant. Materials 4 x Nichrome wire samples (1, 2, 3, 4 m) 1 x Digital Ammeter (±0. 1 A) 1 x Digital Voltmeter (±0. 1 A) 5 Connecting wires 1 x Switch 1 x DC Supply – set to 6 V. 42 | Page Method 1. Construct the measuring circuit as shown below. 2. Connect 1 m length of nichrome wire. 3. Switch on and record voltage and current. 4. Repeat for 2 m, 3 m and 4 m nichrome wire. 5. Conduct 3 trials for each length of wire to ensure consistent V and I measurements. 6. Calculate R using Ohm’s Law. Risk Assessment Electric shock – care should be taken when constructing circuit to ensure that meters have been connected correctly. Power supply should be switched off prior to making any changes to the circuit. Low voltages (6 V) only used. Processing and analysing data and information. Evaluation Complete the Processing and Analysing Data and Evaluation sections for your prac as per the Scientific Method handbook (p. 27 -38) Submit these sections to DEEDS as instructed by your teacher. 43 | Page Ohm’s Law There is an important relationship between Voltage, Current and Resistance in a Circuit: Ohm’s Law 𝑉 Often this is expressed as: 𝐼 = 𝑅 or 𝑉 = 𝐼𝑅. ie. As the resistance _____________increases_____________ for a fixed voltage, the current in the circuit _____________decreases_____________. ie. As the voltage across a resistor is ______________increased_____________, the current ____________ increases_______. 𝑉 Ohm’s Law Calculation Examples: Use 𝐼 = 𝑅 or 𝑉 = 𝐼𝑅 A battery delivers 0.2 A of current to a resistor of 30 Ω. Determine the voltage supplied by the battery. 𝑉 = 𝐼𝑅𝑉 = 0. 2×30𝑉 = 6 𝑉 A 10 Ω resistor is attached to a 6 V battery. Calculate the current in the resistor. A 12 V battery is connected to a resistor and yields a current of 20 mA (0.02 A) Determine the value of the resistor. 𝑉 = 𝐼𝑅12 = 0. 02×𝑅 R = 600 Determine the current in the resistor shown in the 44 | Page  circuit diagram. 𝑉 = 𝐼𝑅10 = 𝐼×1500𝐼 = 0. 0067 𝐴𝐼 = 6. 7 𝑚𝐴 45 | Page PRAC: Ohm’s Law Challenge Aim: To use Ohm’s Law to determine the resistance of an unknown resistor. Materials: Unknown resistor (A, B, C or D), DC Power Supply (2 – 12 V), Ammeter, Voltmeter, Connecting wires. Tasks: 1. Setup a circuit as per the diagram below. [Note: the ammeter is connected in series, the voltmeter is connected in parallel. Note the terminal colours on the diagram]. 2. Starting with the power supply set on 2 V, measure the current passing through the resistor (ammeter) and the voltage drop across the resistor (voltmeter). 3. Increase the voltage incrementally to 12 V, measuring voltage/current pairs. 4. Complete the table below. TABLE OF RESULTS Voltage (V) from voltmeter Current, I (A) 5. Plot a graph of Current (x-axis) vs Voltage (y-axis) on the graph paper provided. 6. Draw a line of best fit through the data points. 46 | Page 7. Calculate the gradient of the line of best fit (Gradient = Rise/Run). This is an estimate of the resistance of the 𝑉 unknown resistor (Recall 𝑅 = 𝐼 ). Estimate of resistance: ___________________________________ 8. Load resistors that have a constant resistance, regardless of the applied voltage, are called ohmic conductors. Otherwise, they are called non-ohmic conductors. What type of conductor is the light globe? ___________________________________ For teachers: R1 = R7 = R13 = 48 Ohm R2 = R8 = R14 = 83 Ohm R3 = R9 = 122 Ohm R4 = R10 = 151 Ohm R5 = R11 = 223 Ohm R6 = R12 = 273 Ohm 47 | Page Circuit Symbols International standards for drawing circuits makes it easier to communicate clearly with other scientists/engineers Note on meters: Ammeters measure current. They are placed “inside” the circuit. Voltmeters measure the difference in voltage between two points, so they are placed outside the circuit. Circuit Drawing Examples Example 1 Draw a circuit showing a 6 V battery, a switch a 180 Ω resistor, globe and switch in series. Show a voltmeter across the resistor and an ammeter after the switch. Face the battery so conventional current would flow clockwise. Example 2 Draw a circuit showing a 12 V battery with a two 360 Ω resistors in parallel. Include a switch with each resistor. Show an ammeter measuring current in each resistor. Show a voltmeter across each resistor. Face the battery so conventional current would flow clockwise. Note that it doesn’t matter if the ammeters or switches are before or after the resistor (see Series Circuit section) 48 | Page Series and Parallel Circuits You should recall that components can be arranged in: Series (where there is only one path for current to follow) Parallel (multiple branches for current) Series Parallel Voltage Distributed between resistors Same for each branch Current Same at any point Distributed between branches Example 1 – Series Circuit Determine the values of A2, A3 and V5 A2 = A3 = total current = 0.3 A V5 = 30 – 15 = 15 V Both resistors are the same value, so voltage is shared evenly Example 2 – Series Circuit Determine the values of A2, A3 , V1 and V2 V1 = 12 V 49 | Page V2 = 12 – 8.0 = 4.0 V Larger resistor has larger voltage in series A2 = A3 = 0.22 A All resistors are in series, so current is constant throughout Example 3 – Parallel Circuit Determine the values of A1, A2 , V2 and V3 V2 = V3 = 6 V A1 = A2 = 0.5 A All resistors are same value so current in each branch is shared evenly Example 4 – Series & Parallel Circuit Determine the values of A1, A2 , V1 and V2 A1 = 2.66 A Current is same in/out battery A2 = 2.67 – 1.33 = 1.33 A Current is shared between two branches V2 = 16 V Parallel circuit V1 = 24 – 16 = 8 V 3 ohm resistor effectively in series with 12 ohm resistors 50 | Page ASSIGNMENT: Series and Parallel Circuit Builder Aim: To use the PhET Circuit Builder to explore the characteristics of Series and Parallel Circuits. Source: PhET Circuit Builder. https://phet.colorado.edu/sims/html/circuit-construction-kit-dc/latest/circuit-construction-kit-dc_all.html Tasks: 1. Download the submission template from DEEDS (GDoc): https://bit.ly/PhETCircuitBuilder 2. Working in pairs, use the Circuit Builder to construct the circuits as indicated. 3. Submit the completed GDoc as instructed by your teacher. 51 | Page Calculating Total Resistance in Series and Parallel We can add to our knowledge of series and parallel circuits be calculating the total resistance For a known voltage supply, this allows us to then determine overall current in the circuit using Ohm’s Law. In a series circuit the resistance of components adds together. In a parallel circuit the total resistance decreases as we add more and more branches to the circuit. 1 Note that we want Rtotal, not 𝑅𝑡𝑜𝑡𝑎𝑙 , so the final formula is: If there are only two branches, there is a simplified formula: Calculate the total resistance in the following circuits: Example 1 52 | Page Example 2 Note the use of the shortcut formula. Also, the effective total resistance of two parallel resistors is half of one. Example 3 53 | Page Example 4 Example 5 54 | Page  Section 2.2: Key Summary Questions 1. Indicate the direction of the current (use I) and electron flow (use e-) in the circuit below: 2. Complete the table below: Quantity Formula symbol Unit Symbol Name Current I A Amperes Voltage V V Volts Resistance R Ω Ohms 3. Complete the table below: Material Conductor or Insulator Resistance (High or Low) Gold Conductor Low Plastic Insulator High Dry Wood Insulator High Copper Conductor Low Glass Insulator High 4. A student measures 0.4 A of electrical current through a globe when she applies a voltage of 12 V. Determine the resistance. 𝑉 12 𝑅= 𝐼 𝑅= 0.4 𝑅 = 30 Ω 5. Calculate the expected current in a circuit of total resistance 25 Ω when a supply voltage of 15 V is used. 55 | Page  𝑉 15 𝐼= 𝑅 𝐼= 25 𝐼 = 0. 6 𝐴 6. Determine the voltage drop across a 180 Ω resistor carrying 0.3 A. 𝑉 = 𝐼𝑅𝑉 = 0. 3 ×180𝑉 = 54 𝑉 7. Calculate the total resistance of the series circuit shown below. 𝑅 = 40 + 60 + 100𝑅 = 200 Ω 8. Calculate the total resistance of the parallel circuit shown below. 20×10 200 𝑅= 20+10 𝑅= 30 𝑅 = 6. 67 Ω 9. Calculate the total resistance of the parallel circuit shown below. 1 1 1 1 1 19 𝑅 = 6 + 10 + 20 𝑅 = 60 𝑅 = 3. 16 Ω 10. (Harder) Calculate the total resistance of the circuit shown below. Parallel 1: 40×40 1600 𝑅= 40+40 𝑅 = 80 𝑅 = 20 Ω Parallel 2: 56 | Page  1 1 1 1 4 𝑅 = 10 + 30 𝑅 = 30 𝑅 = 7. 5 Ω Series (Total): 𝑅 = 20 + 20 + 7. 5𝑅 = 47. 5 Ω 57 | Page 2.3 Electrical Power Power is observed in a number of ways, including: Brightness_____________________ of a globe Speed ____________________________ of a motor Heat ______________________________ of a resistor We have already used a power calculation in the Wind Turbine investigation: 𝑃 = 𝑉×𝐼 𝑃𝑜𝑤𝑒𝑟 (𝑊𝑎𝑡𝑡𝑠) = 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 (𝑉𝑜𝑙𝑡𝑠)×𝐶𝑢𝑟𝑟𝑒𝑛𝑡 (𝐴𝑚𝑝𝑠) Example 1 A wind turbine generates 2.3 A of current at 16 V. Calculate the electrical power generated. 𝑃 = 𝑉×𝐼 𝑃 = 16×2. 3 𝑃 = 36. 8 𝑊 Example 2 A 12 V supply is applied to a 60 ohm resistor, resulting in a current of 0.2 A. Calculate the power dissipated as heat by the resistor. 𝑃 = 𝑉×𝐼 𝑃 = 12×0. 2 𝑃 = 2. 4 𝑊 Example 3 Determine the current drawn by a 1500 W toaster operating on a supply of 230 V. 𝑃 = 𝑉×𝐼 1500 = 230×𝐼 𝐼 = 6. 52 𝐴 58 | Page 3.1 Magnetic Fields The phenomenon of magnetism has been known since the ancient Greeks. The idea of a magnetic field was first put forward by Michael Faraday (1791 – 1867). A field is a region in three-dimensional space in which a body experiences a force due to gravity, magnetism or electricity. The shape of the magnetic field is revealed by magnetic field lines, which can visualised by scattering iron filings around a magnet. These field lines spread out from one pole, curve around the magnetic, and return to the other pole. A few elements in the periodic table can form “permanent” bar magnets, either naturally or by subjecting samples to a strong magnetic field. Elements: IRON, NICKEL, COBALT The direction of the field outside the magnet is from the North pole to the South pole. There are two rules for drawing field lines: 1. Field lines do not intersect. 2. Each field line is a continuous loop that leaves the north pole of the magnet, enters at the south pole, and passes through the magnet back to the north pole. The strength of the magnetic field is represented by the closeness of the field lines. That is, the closer the lines, the stronger the field. 59 | Page Your turn: Practice drawing field lines around the bar magnets depicted below: Other Magnetic Field Shapes All magnets have a North and a South pole, but depending on their shape, the poles will be located at different positions. Pairs of magnets will influence neighbouring fields 60 | Page PRAC: Sketching Magnetic Fields Aim: To investigate the nature of magnetic fields around bar magnets and to gain experience in working with the concept of field lines in general. Apparatus: 2 bar magnets, plotting compasses, iron fillings in oil. Method – use this to complete sketches for the four configurations shown below: 1) Place magnets underneath the iron fillings / oil visualisers. 2) Draw the pattern. 3) Now take the sheet of paper away without moving the magnets. 4) Position a plotting compass near the magnets and slowly move it around the magnet only in the direction indicated by the compass. This allows you to follow a field line and further obtain the direction of the magnetic field. 5) The plotting compass points in the direction of the magnetic field at the point at which it is placed. The iron-filling pattern gives you an idea of the shape of the magnetic field. Therefore, by moving a plotting compass around in a magnetic field and observing the direction in which it points, the nature of the whole field can be determined. 61 | Page Properties of Magnets Forces on magnets o When opposite poles of two magnets are brought together, the two magnets will be attracted o When like poles of two magnets are brought together, the two magnets will be repelled. UNLIKE POLES _________ATTRACT_______ LIKE POLES _________REPEL_______ Dipoles o If a bar magnet is broken in half, a North and a South pole will form on each magnet. o As such, it is not possible to create a monopole magnet (a magnet with only one pole). Therefore, magnets will always form a dipole. Earth’s Magnetic Field o The Earth has a dipolar magnetic field which acts like a huge bar magnet. o A compass magnet is free to align itself with the Earth’s magnetic field. o Compasses will “point” to the magnetic north pole, which is slightly offset from the geographic north pole. o The rules of field lines effectively means that there is an inverted bar magnet inside the Earth. 62 | Page  More information on magnetics: https://www.eclipsemagnetics.com/resources/guides/a-quick-guide-to-magnets-magnetic-metals-and- non-magnetic-metals/ Section 3.1: Key Summary Questions 1. Draw 6 continuous field lines joining the poles of the bar magnet shown below. Use arrows to show the direction of the field lines. 2. Draw 6 continuous field lines joining the poles of the bar magnets shown below. Use arrows to show the direction of the field lines. 63 | Page  3. Would the magnets shown in Q2 be attracted or repelled from each other? Attracted (Opposite poles) 4. Are magnets monopole or dipole in nature? Dipole (always!) 5. The diagram below shows field lines around a pair of bar magnets. Identify the direction that a compass would point if placed at various points near the pair of magnets. Point Direction A LEFT B UP C LEFT D LEFT 64 | Page 3.2 Electromagnetism When current is passed through a conductor, a ____ temporary, circular ________shaped magnetic field is created A compass will follow the field lines in the same way. We use the Right-Hand Grip rule to show the direction of the field The thumb indicates the direction of conventional current in the wire The fingers wrap around the wire in the direction of the magnetic field To help visualize magnetic fields around a current carrying wire, we use some drawing conventions. If current or field lines are directed “out of the page”, we use: If current or field lines are directed “into the page”, we use: DEMO TIME! Current around a wire with compasses to show direction 65 | Page 3.3 Electric Motors The Magnetic Force When the magnetic field around a wire interacts with an external magnetic field (e.g. bar magnets), a force results Direction of the magnetic force If we know the direction of the current in the wire and the direction of the magnetic field, we can determine the direction of the magnetic force on a wire, using the right-hand slap rule. Right-hand slap rule: Thumb points in the direction of conventional current Fingers point in the direction of the magnetic field (North to South) Palm points in the direction of the magnetic force Apply the Right-Hand Slap Rule to determine the direction of the force on the wire in the example shown right. Applet demo: https://www.walter-fendt.de/html5/phen/lorentzforce_en.htm 66 | Page  Apply the Right-Hand Slap Rule to determine the direction of the force on the wire in the following examples: 1. Answer: UP 2. Answer: DOWN 3. 4. Answer: RIGHT Answer: RIGHT 67 | Page Electric Motors DC Motors utilise the Magnetic Force to achieve rotation/ Force is up on one side of the coil and down on the other – creating rotation. Supplies voltage to create current in the circuit Battery Brush Connect battery to coil Contact Creates magnetic field to interact with external magnets Coil _______________________________________________________________________________________________ Required to reverse current every half-turn (more later) Commutator Note: In the diagram above (Near N pole), Field = Right, Current = Out of the page, Force = Up. Simplified Animation: https://www.walter-fendt.de/html5/phen/electricmotor_en.htm Note that the force on the coil of wire needs to be reversed every half-turn to ensure the motor turns continuously. This is done with the commutator (split ring). 68 | Page PRAC: Investigating Motors Aim: To investigate the operation of electric motors, both commercially made and improvised. Materials: Bar magnets Demo motors (working) Demo motors (for disassembly) Cables 2-12 V DC supply (5 A) DIY Motor Kits Task A: Commercial Motor 1. Connect the motor to the 4 V DC source. The shaft should begin to spin quite fast. Reverse the connection to the battery. What happens? Motor spins in the opposite direction 2. Increase the voltage to 6 V and then 8 V. Describe the effect on the motor. Motor spins faster Task B – Improvised Motor 1 – Show Image. 1. Use the disassembled components of the motor to recreate its operation as demonstrated by your teacher. a. Pen at each end of the axle. b. Pair of bar magnets either side of the coil (close but not touching). c. Two plugs clips connected to a DC supply – touching either side of the commutator. 2. Describe the operation of the improvised motor. 69 | Page  Coil spins fast. Speed will increase if magnets brought closer to the coil 3. Why do you think there so many coils of wire on each winding? Increase the size of the force as more turns in the coil leads to a larger internal magnetic field 4. Commercial motors often use curved magnets rather than rectangular bar magnets. What is the advantage of the curved magnets? Curved magnets can be brought closer to the spinning coil without touching it. Task C – Improvised Motor 2 In this task, you are going to assemble an improvised DC motor. Some of you may recall this from Year 7 Orientation – let’s see if you can do better than them! Ensure that your DIY Motor Kit has the following materials: a. D-Cell Battery. b. Copper wire c. Wooden dowel d. Rubber bands e. Neodymium magnet. f. 2 safety pins g. Sand paper Follow the following method to create your motor: 1. Wind about 8-10 turns of copper wire around the wood dowel. Leave about 4 cm of wire at either end. 2. Tie the ends around the loop as shown and straighten the bits that stick out. 70 | Page  3. Attach the two safety pins to the battery with the rubber band, ensuring that the pins are touching the terminals. 4. Arrange the coil in the loops in the safety pins as shown. Bend the wires, if necessary, until it is well balanced and rotates freely. 5. Take the coil out and sand off the insulation from half of circumference of the wire. Ensure that the bared halves are on the same side of the wire. Sand the wire at each end right up to the coil. 6. Return the coil to the support. Place the magnet on the battery and see if the coil turns. 71 | Page  7. Troubleshooting: a. Gently flick the motor to see it starts rotating, b. Try reversing the coil or taking it out and re-balancing it c. Experiment with the position of the coil relative to the magnet d. Check to see that the area you sanded is free of insulation e. Check that safety pins are in contact with the terminals of the battery 72 | Page  Section 3.3: Key Summary Questions 1. Use RH grip rule to show direction of field around the current-carrying wires shown below. 2. Label the simplified diagram of the motor shown below. Use the terms: Brush, Battery, Coil, Commutator. 3. Referring to the diagram above, the current is indicated by the arrow heads labelled on the conducting wire. a. Use arrows to indicate the direction of the forces on the sides of the coil. b. Use a curved arrow to indicate the direction of rotation of the coil. 73 | Page 74 | Page