Physics Unit 3. Year 8 Electromagnets Year 8 Light and Sound Year 9 Generating electricity P1- Electricity ad National grid

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1 Number of weeks (between 6&8) Content of the unit Assumed prior learning (tested at the beginning of the unit) 18 lessons Approx. 7 weeks Medical imaging (x-rays, ultrasound, endoscope) Refraction and lenses Moments and levers Electromagnetism Motors and generators Year 8 Electromagnets Year 8 Light and Sound Year 9 Generating electricity P1- Electricity ad National grid Assessment points and tasks Written feedback points Learning Outcomes (tested at the end and related to subject competences) P3.1.1 X-rays 6 mark question x3 Diagnostic marking on 6 mark Compare the wavelength of X-rays to the diameter of an atom Exam question homework question Describe how X-rays affect photographic film, and how they interact with bone and tissue each week End of chapter assessment Outline some uses of X-rays for diagnosis and treatment of some medical conditions (including charge-coupled devices, or CCDs) End of chapter assessment feedback Outline the precautions that needed when using X-ray machines and CT scanners (exam questions) P3.1.2 Ultrasound Define ultrasound in relation to the range of human hearing Describe how ultrasound waves can be partially reflected when they meet a boundary between one medium and another, and how the time taken for reflections to reach a detector can be used Calculate the distance between interfaces in various media using: s = v x t Use data from oscilloscope traces in the above equation Give examples of how ultrasound waves can be used in medicine Compare the medical use of ultrasound and X-rays Evaluate advantages and disadvantages of using ultrasound, X-rays and CT scans P3.1.3 Lenses Define the term refraction and state that a lens forms an image by refracting light Describe the effect of a convex or converging lens on parallel rays of light Define the term focal length Calculate the refractive index using angles of incidence (i) and refraction (r) Describe how the nature of an image is defined by its size relative to the object, whether it is upright or inverted and whether it is real or virtual Describe the nature of images produced by a converging lens for an object placed at different distances to the lens Outline the use of converging lenses as magnifying glasses Describe the nature of an image produced by a concave or diverging lens Construct ray diagrams to show the formation of images by converging and diverging lenses, and complete such diagrams drawn on graph paper Draw and interpret ray diagrams in order to determine the nature of the image P3.1.4 The eye Describe the structure of the eye, including the functions of the retina, lens, cornea, pupil/iris, ciliary muscle and suspensory ligaments Explain how long sight and short sight are causes, and how convex and concave lenses can be used to correct such vision to produce an image on the retina Page 1 of 11

2 Evaluate the use of different lenses for the correction of defects of vision Describe the range of vision in terms of near point and far point, including distances Compare the structure of the eye with a camera Calculate the power (P, expressed in dioptres, D) of a lens using the equation: P = 1 / f Explain how the focal length of a lens is determined using the refractive index of the material and the curvature of the two surfaces of the lens (HT) Relate the flatness of a lens to its refractive index, allowing for thinner lenses P3.1.5 Other applications using light Describe total internal reflection and explain what is meant by critical angle (c) (HT) Calculate refractive index as 1 / sin c Give examples of how visible light can be sent along optical fibres P3.2.1 Centre of mass Define the term centre of mass and describe how to find the centre of mass of a thin, irregular sheet of a material Describe what will happen to an object that is freely suspended State that the centre of mass of a symmetrical object is along the axis of symmetry Calculate periodic time (T) for a pendulum using T = 1 / f State that the time period of a pendulum depends on its length P3.2.2 Moments Describe moment as the turning effect of a force Calculate the size of a moment (M) using M = F x d Explain why an object is not turning, in terms of clockwise and anticlockwise moments (HT) Calculate the size of a force or distance from pivot, acting on a balanced object Outline the use of simple levers as force multipliers (HT) Explain why a body will tend to topple if the line of action of the weight of an object lies outside the base of the object, because their will be a resultant moment Analyse the stability of objects by evaluating their tendency to topple, using a range of laboratory equipment to model real-life situations, such as cranes Explain how width of base and position of centre of mass affect the stability of an object P3.2.3 Hydraulics State that liquids are virtually incompressible, and the pressure in a liquid is therefore transmitted equally in all directions (to all other points in the liquid) Explain how a hydraulic system can be used as a force multiplier when there are different cross-sectional areas on the effort and load side of the system Calculate the pressure in different parts of a hydraulic system using P = F x A P3.2.4 Circular motion Explain that an object moving in a circle continuously accelerates towards the centre of the circle, which changes the direction of motion but not the speed of the object Describe the resultant force as the centripetal force, which is always directed towards the centre of the circle, and identify which force(s) provide(s) the centripetal force in a given situation Describe how the centripetal force needed to make an object perform circular motion increase as: the mass increases, the speed increases, the radius of the circle increases Interpret and evaluate data on objects moving in circular paths, remembering that the centripetal force does not exist in its own right, but is Page 2 of 11

3 always provided by something else (such as gravitational force, friction or tension) P3.3.1 The motor effect State that a magnetic field is produced around a wire when a current flows through it Give examples of applications of electromagnets, such as cranes for lifting iron/steel Describe the principle of the motor effect and its use in any given situation Outline how the motor effect creates movement in electric motors Explain two ways that the size of the force can be increased State that a conductor will not experience a force if its is parallel to the magnetic field Identify the direction of the force using Fleming s left-hand rule State that the direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed Interpret diagrams of electromagnetic appliances in order to explain how they work P3.3.2 Transformers Describe how a potential difference is induced across the ends of an electrical conductor when it cuts through a magnetic field Describe how a potential difference is induced across the ends of a coil if a magnet is moved into a coil of wire Outline the basic structure of a transformer Outline how an alternating current in the primary coil produces a changing magnetic field in the iron core and hence in the secondary coil, which in turn induces an alternating potential difference across the ends of the secondary coil Compare the potential difference across the primary and secondary coils in step-up and in step-down transformers Relate the potential difference across the primary and secondary coils of a transformer using the equation: Relate electrical power input and output for tranformers, assuming they are 100% efficient, using the equation: State that switch mode transformers operate at a high frequency, often between 50 khz and 200 khz Explain the advantages of switch mode transformers working from a 50 Hz mains supply in terms of size and weight, and why this makes them useful for applications such as mobile phone chargers State that switch mode transformers use very little power when they are switched on but no load is applied Compare the use of different types of transformer for a particular application. Examples might include mobile phones chargers and power supplies for laptops Page 3 of 11

4 Lesson Clear learning intentions (KQ) Clear success criteria (Bands) (Keywords) Hook (starter) Presentation of content (teacher input) Guided practice (pupil activities) Requisition (per group) Independent practice (homework) Closure (AfL) P3.1 Medical application of Physics 1. X-rays How are X-rays used medically? Know that X-rays affect a photographic film in the same way as light, are absorbed by metal and bone but are transmitted by healthy tissue. Understand that X-rays can be used for diagnosis of bone fractures and dental problems, in computerised tomography (CT) scans, and in treatment by killing cancer cells. Can you recall the order of the electromagnetic spectrum? Recap EM spectrum. Elicit what pupils know about x-rays already. Video/animation of how x- ray images broken bones. Discussion over dangers of ionising radiation. Recall EM spectrum. Describe how x-rays image broken bones. Evaluate dangers of x-rays. Exam questions. Set P3.1 homework booklet Due in 7 lessons X-rays true or false (mini-whiteboards) 2. Ultrasound Why is ultrasound used to image pregnant women? Know that the use of CCDs allows images to be formed electronically. Know that the range of human hearing is about 20 Hz to Hz and that sound waves of higher frequencies are referred to as ultrasound. Understand the principle of ultrasound echoes. Use the equation to calculate distances between interfaces and use data from diagrams of oscilloscope traces. Fill in the gaps sound recap from year 8 and P1. Elicit what pupils recall about sound from year 8 and P1. Carry out pupil hearing test. Discuss human hearing range and ultrasound. Feedback from research on uses of ultrasound. Pupils complete hearing test and record human hearing range. Pupils use information to research uses of ultrasound. Past paper question. Treasure hunt use knowledge of ultrasound to find treasure using radar data. Page 4 of 11

5 3. 6 Mark Question What are the advantages and disadvantages of x-rays and ultrasound? 4. Refraction Why does light bend when it passes through a medium? 5. TIR How do optical fibres work? Evaluate the medical use of ultrasound and X-rays, including an understanding that some of the differences in use are because ultrasound waves are non-ionising and X-rays are ionising. Compare the advantages and disadvantages of using ultrasound, X-rays or CT scans in terms of safety issues and the quality of image formed. Understand that light is refracted when passing from one medium to another. Use the equation for refractive index. Understand how a lens refracts light. Understand the concept of total internal reflection and critical angle. HT only Understand and use the relationship between refractive index and critical angle. State 2 facts about x- rays and ultrasound What are the colours of the rainbow? How does a rainbow occur? Is it possible for the refractive index of a material to be less than one? Discuss and explain. Recap key points of x-rays and ultrasound. Introduce 6 mark questions and discuss approach. Show 2 example pupil responses. Pupils discuss which is best and why. 6 MQ: Compare and evaluate the use of x-rays and ultrasound for medical imaging. Feedback from starter to gauge pupils recollection of refraction. Demonstrate refraction of prism and discuss. Demo experiment. Introduce refractive index. Discuss starter as a way of recapping previous lesson. Demo critical angle experiment. Discuss what critical angle and TIR are. Pupils plan and complete 6 mark question. Pupils carry out refraction experiment (10 mins max just to experience refraction and record 1 set of angles) Pupils define refraction. Pupils practice refractive index calculations. Pupils carry out practical to find critical angle. Pupils draw diagrams to show critical angle and TIR. HT- practice critical angle calculations Demo: Prism, power pack, leads, light box Exp: Power pack, light box, leads, square glass block, protractor, white paper. Exp: Power pack, light box, leads, semi-circular glass block, protractor, white paper. Peer- assess SPAG. Teacher to mark 6 mark questions and give diagnostic feedback. Refraction True/false 1 minute door-to-door salesman style pitch to sell optical fibre broadband to customers HT- calculate critical angle from refractive index Pupils draw and explain how optical fibres work Discuss application of optical fibres and endoscopes Page 5 of 11

6 6. Lenses What is a lens and what does it do to an image? 7. Using Lenses How can I draw ray diagrams to represent the behaviour of light through a lens? Understand the terms associated with lenses, which includes convex, converging and diverging, principal focus and focal length. Understand the terms associated with images, which include upright and inverted, real and virtual, enlarged and diminished. Use the magnification equation. Know the nature of the images formed by a converging lens when the object is at different distances from the lens, and the imaged formed by a diverging lens. Draw diagrams to show the nature of the images formed by a converging lens when the object is at different distances from the lens, and the imaged formed by a diverging lens. Give one advantage and disadvantage of using endoscopes to perform laparoscopic surgery. Show an image produced by a lens and ask pupils to describe it. Ext: What sort of lens would produce this image? Introduce lenses. Show pupils concave and convex lenses. Explain words used to describe images in lenses. Explain practical. Go over magnification equation. Go through the 2 main rays to draw for a lens diagram. Do 1 example. Go over all ray diagrams. Prompt pupils for a use of each example. Pupils label lens diagram with keywords and define each of the image description words (magnified, diminished, upright, inverted, real, virtual) Pupils investigate images in lenses and describe. Pupils calculate magnification. Pupils complete all ray diagrams for concave and convex lenses. Pupils give use of each one. Exp: Concave lens, convex lens, candle, screen Keyword match-up Self-assess ray diagrams. Page 6 of 11

7 8. The eye How does the eye work? Know the function of parts of the eye: retina, lens, cornea, pupil/iris, ciliary muscle and suspensory ligaments. Exam style ray diagram question. Instruct pupils how can find human viewing range. Go over structure of the eye. Pupils investigate and record viewing range. Pupils label diagram of eye. Compare eye to camera. Understand how the action of the ciliary muscle causes changes in the shape of the lens, which allows the light to be focused at varying distances. Know that the near point is approximately 25 cm and the far point is infinity Use the equation for the power of a lens, where P is power in dioptres (D) and f is focal length in metres (m). Discuss long-sighted and short-sighted and how glasses help. Look at power equation. Discuss how lenses can be made thinner. Pupils describe how eye focuses. Pupils draw ray diagrams to show how glasses correct vision. Pupils write down power equation and discuss how lenses can be made thinner. 9. End of Chapter Test What grade am I working at? Be aware that the film in a camera or the charge-coupled devices (CCDs) in a digital camera is the equivalent of the retina in the eye. Complete end of unit test Peer-assess homework as revision activity Conduct test Pupils complete test P3.2 Using Physics to Make Things Work 10. Moments How does a lever work? Understand how a lever can be used as a force multiplier. Understand the concept of a turning moment and use the equation. HT only Perform calculations involving moments and balanced objects. Show a picture of a hammer. Where should you hold a hammer to get the maximum force? Why? Introduce concept of level. Give moment equation. Discuss how we can interpret this in terms of levers. Pupils define moment. Pupils describe how levers help to do work in terms of moments. Pupils complete simple moments calculations. Set P3.1 homework booklet Due in 6 lessons Calculations quiz (minwhiteboards) Page 7 of 11

8 11. Balancing (HT only) 11. Centre of Mass (6 mark question) How do objects balance? How can we make objects more stable? HT only Perform calculations involving moments and balanced objects. HT only Use the idea of a resultant moment leading to toppling as applied to vehicles and simple balancing toys. Describe how to find the centre of mass of a thin, irregular sheet of a material. Analyse the stability of objects by evaluating their tendency to topple. Understand that objects with a wide base and low centre of mass are more stable than those with a narrow base and a high centre of mass. Show a picture of a seesaw. Why is it balanced? Simple moment calculation Go through more complex moments examples. Set challenge to find weight (or mass) of a 2p coin. Show video of balancing tricks (fork on glass using matchstick) atch?v=4w4sxje7by8&safe= active Introduce idea of centre of mass. Explain practical to find centre of mass. Discuss 6 mark questions structure 6 MQ: Describe how you find the centre of mass of an asymmetrical object. Pupils complete HT calculations on moments. Pupils use masses and balances to find weight of 2p coin. Pupils define centre of mass. Pupils find centre of mass of symmetrical shapes. Pupils carry out practical to find centre of mass (10 mins max.) Pupils complete 6 mark question to describe experiment. Pupils explain how to stabilise an object. Moments see-saw, 10g masses, 2p coin Clamp stand, string, bung, asymmetrical shapes cut out of card Progress check on moments Peer- assess SPAG. Teacher to mark 6 mark questions and give diagnostic feedback. Discuss stability in terms of tightrope walker, double decker bus. Page 8 of 11

9 12. Hydraulics 13. Centripetal Force 14. Pendulums How does a hydraulic brake work? What keeps the Earth in orbit around the Sun? How does a pendulum work? 15. End of What grade am I Chapter Test working at? P3.3 Keeping Things Moving Understand that a force exerted at one point on a liquid will be transmitted to other points in the liquid. Understand the action of a hydraulic machine. Use the equation to calculate pressure. Understand why an object in circular motion accelerates towards the centre of the circle, and what is meant by centripetal force. Understand that a centripetal force does not exist in its own right but is always provided by other forces such as gravitational force, friction or tension. Be able to identify which force(s) provide(s) the centripetal force in a given situation. Use the equation for time period and frequency. Know some applications of the pendulum, such as simple fairground and playground rides. Complete end of unit test Show a picture of a camel. How do camels walk on sand without sinking? Show a picture of a roundabout in a playground. What forces are acting on the children on it? Give 3 everyday examples of a pendulum Peer-assess homework as revision activity Introduce concept of pressure and give equation. Go through example questions. Demo: Lifting brick using hydraulic syringes. Discuss pressure in liquids and how hydraulics work. Show how to use pressure equation to find force exerted by slave piston in hydraulic system. Bucket of water challenge: Can you swing a bucket of water over your head without getting wet? How? Discuss ideas. Go over centripetal force and factors that can increase it. Look at real world examples. Introduce idea of pendulum. Discuss what could affect time period. Introduce pendulum investigation. Discuss playground swing application. Conduct test Pupils complete pressure calculations. Pupils define hydraulic system, label diagram and explain how it ca be used as a force multiplier. Pupils complete calculations on force of slave piston. Pupils use bung on string to understand centripetal force. Pupils explain how they could carry out bucket challenge (can do if playground is available). Pupils explain centripetal force in one real world example. Pupils complete exam questions. Pupils label diagram and define keywords. Pupils investigate factors that affect time period. Pupils explain how playground swing acts as pendulum. Exam questions. Pupils complete test Demo: large syringe, small syringe, brick 9or heavy object, tripod (no gauze) 3 sizes of bung on string, metre ruler Pendulum (heavy weight) of string (2 sizes), stop clock, metre ruler Show various uses of hydraulics. Pupils choose one and explain how it works. Sentence starters on centripetal force for pupils to complete. Centripetal force is It is affected by A real world example is Peer-assess exam questions Page 9 of 11

10 16. Electromagn ets How can we use electromagnets to move heavy objects? Understand that a current in a conductor produces a magnetic field and that this is the basis for electromagnets, applications of which include their use on cranes for lifting iron or steel. Write down 3 facts about magnets that you can remember from year 8. Feedback from starter to gauge pupils understanding. Introduce experiment to investigate factors that affect electromagnets. Pupils use iron fillings to sketch field around bar magnet. Pupils investigate factors that affect electromagnets. Explain your application to a partner. 17. The Motor Effect 18. DC Motors 19. Induction What is the motor effect? How does a motor work? How does a coil and magnet produce an electric current? Understand the principle of the motor effect and know how to use Fleming s Left-hand Rule to identify the direction of the force produced. Know how the size and direction of the force produced can be altered. Explain how a DC motor works based on the principle of the motor effect. Understand the principle of electromagnetic induction. List 3 objects that use a motor. What energy transfer takes place In a motor? Left-hand rule example question. What 2 ways can you reverse the direction of a motor? What 3 ways can we increase the strength of a motor? Discuss applications such as cranes and door bells. Demonstrate the motor effect using a U-shaped magnet and graphite rods. Discuss factors that could affect motor effect. Explain use of Fleming s lefthand rule. Go over starter and recap from last lesson. Demo motor in action. Explain role of brushes and split-ring commutator. (Note pupils can make motor If time) Demonstrate induction using coil and magnet. How is it similar and different to motor effect? What could increase amount of voltage induced? Show animation of AC generator. Discuss how to increase voltage and what happens if coil spins faster in terms of frequency of current. Discuss role of slip rings. Pupils choose one application and describe how it works. Pupils describe motor effect. Pupils describe how motor effect can be increased. Pupils practice using Fleming s left hand rule. Exam questions. Pupils label DC motor diagram. (Pupils make motor- this can take up to 30 minutes!) Pupils explain role of split ring commutator. Pupils label AC generator. Pupils explain why AC is generated. Pupils describe how to increase size of induced voltage. Pupils explain role of slip rings. Past paper question. Simple electric motor kit dation.org/practicalphysics/electric-motor C-coil, insulated wire, bar magnet, galvanometer demo dation.org/practicalphysics/magnet-movingnear-coil-c-core Progress check on motor effect and motors. Motor or generator? Mini-whiteboards Page 10 of 11

11 20. Transformer s How does a transformer increase or decrease voltage? Understand the structure of the transformer. Explain how a transformer works. Understand the difference between a step-up transformer and a step-down transformer. Use the transformer equation. What is the national grid? Can you list all components and explain their role? Feedback from starter to gauge recollection from P1.3. Recap step-up and stepdown transformers. Demo transformer noting down no. of coils on primary and secondary. Pupils define step-up and step-down transformer. Pupils explain why voltage is stepped up in power lines. Pupils use transformer equation to complete questions. Model Transformerhttp:// dation.org/practicalphysics/modeltransformer Pupils list stages of national grid and explain each part. 21. Switch Mode transformers (6 Mark Q) What are the advantages and disadvantages of a switch mode transformer? Understand the difference between a switch mode transformer and a conventional transformer. Know the advantages and uses of switch mode transformers. What is the voltage and frequency of mains electricity in the UK? Show transformer equation. Explain how transformer works. Introduce switch mode transformer. Give pupils information about iron core transformer and switch mode transformers for research. Pupils explain how a transformer works for 5 marks. Pupils use information to research similarities, differences, advantages and disadvantages of 2 types of transformers. Pupils complete 6 MQ. Peer- assess SPAG. Teacher to mark 6 mark questions and give diagnostic feedback. Discuss approach to 6 mark question. 15. End of Chapter Test What grade am I working at? Complete end of unit test Peer-assess homework as revision activity 6 MQ: Compare and evaluate iron core and switch mode transformers. Conduct test Pupils complete test Page 11 of 11