Electricity. Scheme of Work

Transcription

1 Electricity Scheme of Work

2 WHAT IS ELECTRICITY? Electricity is a force of nature and it has been around since the creation of the universe. Electricity, an effect of the electromagnetic force, is the flow of charged particles (electrons) through conductive materials. Electricity, like water, flows from a higher electrical potential to a lower electrical potential. Almost every form of technology is made possible due to electricity and it is an integral part of biological life on Earth. From the beating of our hearts, to the working of our brains and muscles, everything is made possible due to electric currents. Since ancient times, people have come across instances of electricity in nature. Here are some recorded events where electric phenomena were observed: The earliest mention of electricity is found in ancient Egyptian texts from about 2750 BC (roughly 4750 years ago). These texts talk about electric fish that were known as Thunderers of the Nile and defenders of other fish. These electric fish like catfish and torpedo rays have been found in Greek, Roman and Arabic chronicles. Many ancient civilizations have reported the attractive effect that amber has on light objects like feathers when rubbed against cat fur. The magnetic effect of minerals like magnetite was known to the ancient Greeks. Around 600 BC, a Greek philosopher, Thales of Miletus, investigated the static electric effect of amber and wrongly classified it as a magnetic effect arising out of friction. However, later in modern times, electricity and magnetism were proved to be the two manifestations of a single force of electromagnetism. The first indirect evidence of reported similarity between lightning and the electric current delivered by electric fish is found in the name given by Arabs in 15th century to these fish. The name is same as the word for lightning. After that, in 1600 AD, an Englishman named William Gilbert studied both the phenomena of electricity and magnetism and distinguished between the electric effect of amber and magnetic effect of lodestone. It is he who gave the name electricus (Latin) to the phenomenon of attraction showed by amber. Not surprisingly, it was derived from the ancient Greek word for amber, which was elektron. In the 18th century, Benjamin Franklin is supposed to have first proved conclusively that lightning was indeed electricity, through some kite experiments. In the year 1791, Luigi Galvani proved that nerves conduct signals to the muscles in the form of electric currents, thus giving rise to the science of bio-electricity. Version /02/16 Page 1

3 Later in 1800, one of the first electric batteries was created by Allesandro Volta. Later, Hans Christian Ørsted and Andre Ampere proved the unity between electricity and magnetism and Michael Faraday invented the first electric motor. James Clerk Maxwell, through his theory of electromagnetism, conclusively proved the link between electricity and magnetism and proved that light was an electromagnetic wave. The basic devices used to produce electricity are generators; these devices convert mechanical energy into electrical energy. Generators use the relationship between magnetism and electricity. A large magnet is positioned so that when it rotates, an electric current is induced in each section of wire. All of the currents in each wire when summed up equal a current of considerable size. Several different types of electrical generating units are operated with a wide range of fuel sources. Electricity power stations use turbines, engines, or water wheels to convert mechanical or chemical energy to electricity by driving an electric generator. The most common methods of generating electricity are by the use of steam turbines, internal-combustion engines, gas combustion turbines, water turbines and wind turbines. Batteries are the most common source of power used for electrical circuits in schools. They come in a variety of sizes, which can be combined in series battery holders. This allows the voltage produced to be equal to the sum of the batteries used. The timeline shows how devices using electricity have been developed over the past 40 years. bit.ly/electronics-timeline Image credit Permuto Version /02/16 Page 2

4 Different Sources of Electrical Energy Version /02/16 Page 3

5 Famous Scientists who studied Electricity Benjamin Franklin Charles Coulomb Alessandro Volta Andre Ampere Hans Christian Ørsted Michael Faraday James Clerk Maxwell Shortened web link (Type these) bit.ly/bf-electricity bit.ly/coulomb bit.ly/volta-electricity bit.ly/ampere-electricity bit.ly/oersted-electricity bit.ly/faraday-electricity bit.ly/maxwell-electricity Hans Christian Ørsted: The Discovery of Electromagnetism in 1820 On 21 April 1820, during a lecture, Ørsted noticed a compass needle deflected from magnetic north when an electric current from a battery was switched on and off, confirming a direct relationship between electricity and magnetism. His initial interpretation was that magnetic effects radiate from all sides of a wire carrying an electric current, as do light and heat. Three months later he began more intensive investigations and soon thereafter published his findings, showing that an electric current produces a circular magnetic field as it flows through a wire. This discovery was not due to mere chance, since Ørsted had been looking for a relation between electricity and magnetism for several years. The special symmetry of the phenomenon was possibly one of the difficulties that retarded the discovery. It is sometimes claimed that Gian Domenico Romagnosi was the first person to find a relationship between electricity and magnetism, about two decades before Ørsted's 1820 discovery of electromagnetism. However, Romagnosi's experiments did not deal with electric currents, and only showed that an electrostatic charge from a voltaic pile could deflect a magnetic needle. His researches were published in two Italian newspapers and were largely overlooked by the scientific community. Ørsted's findings stirred much research into electrodynamics throughout the scientific community, influencing French physicist André-Marie Ampère's developments of a single mathematical formula to represent the magnetic forces between current-carrying conductors. Ørsted's work also represented a major step toward a unified concept of energy. In 1822, he was elected a foreign member of the Royal Swedish Academy of Sciences. Version /02/16 Page 4

6 ELECTRICITY KEY VOCABULARY KEY FACTS AND DEFINITIONS Alarm Motor Charge - is a physical property of matter that causes it to experience a force when near Alternative Multimeter other electrically charged matter. Electric charge has two types, positive and negative. And these are called protons and electrons. Attract Negative Battery Burglar Buzzer Charge Circuit Coil Component Conductor Current Digital Dynamo Electrical Cell Electricity Electrode Electrolyte Electromagnetic Electron Generator Homopolar Insulator Intense Parallel Photovoltaic Positive Repel Rotating Sensor Series Shock Solar Source Spark Static Van der Graaff Voltage Sir Michael Faraday Hans von Oersted Nicolai Tesla Alessandro Volta Luigi Galvani James Clerk Maxwell Current - Electric current is the rate of charge flowing past a given point in an electric circuit, the unit of current is the ampere or amp. Electrode - An electrode is a conductor through which electric current is passed. Electrodes may be wires, plates, or rods. Electron - is a subatomic particle with a negative electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. It has the symbol e- Van der Graaff - an electrostatic generator which uses a moving belt to accumulate very high voltages on a hollow metal sphere. Voltage - Voltage is electric potential energy per unit charge, measured in joules per coulomb - which is the same as volts. Or more simply how much work can be done by a flowing quantity of current. Version /02/16 Page 5

7 National Curriculum Requirements taught during this unit Identify common appliances that run on electricity. Construct a simple series electrical circuit, identifying and naming its basic parts, including cells, wires, bulbs, switches and buzzers. Identify whether or not a lamp will light in a simple series circuit, based on whether or not the lamp is part of a complete loop with a battery. Recognise that a switch opens and closes a circuit and associate this with whether or not a lamp lights in a simple series circuit. Recognise some common conductors and insulators, and associate metals with being good conductors. Associate the brightness of a lamp or the volume of a buzzer with the number and voltage of cells used in the circuit. Compare and give reasons for variations in how components function, including the brightness of bulbs, the loudness of buzzers and the on/off position of switches. Use recognised symbols when representing a simple circuit in a diagram. Version /02/16 Page 6

8 ASSESSING PUPIL PROGRESS Assessment Foci Opportunities for Assessing in this Unit Can use the SC1 planning sheet to explain what question they are investigating. Thinking scientifically Be able to draw the force fields around a simple bar magnet. Using the particle model of materials to explain pressure in detail. Be able to explain how parachutes help save lives. Understanding the applications and implications of science Explain some of the benefits of rockets in society. Describe how the design of cars has changed to reduce friction. Can distinguish between evidence and opinion in each of the investigations. Communicating and collaborating in science Can use force arrows when describing the forces on a parachute. Explain why it is necessary for scientists to 'review' each other's work. Can complete the Sc1 Planning sheet with simple Variables identified. Using investigative approaches Can suggest good examples of how to improve their experimental design. State simply what their results from investigations appear to suggest. ORK Working critically with evidence Base conclusions from their results in various formats e.g. line graphs. Students can confidently say how their data was precise and accurate. Version /02/16 Page 7

9 ELECTRICITY SCHEME OF WORK Lessons 1 & 2: Introduction to Electricity Lesson 1: Teacher Demonstrations & Key Knowledge & Learning Objectives D1.1: Bar Magnets + Van der Graaf Generator D1.2: Bending Water Learn that electricity in the home or power stations can mean the movement of small particles or charges called electrons and protons and that these move slowly through the wires in homes and offices and in electrical devices. Learn that static is a type of electricity. Static electricity can be produced by rubbing two objects together or simply placing different objects together. Learn that, like magnets, electric charges always have invisible electric fields this can be modelled using a magnet. Learn that like charges repel and unlike charges attract and that this can be used to explain a variety of electrical phenomena. Lesson 2: Children s Investigations & Key Questions I2.1: Super Sparker I2.2: Charging Balloon I2.3: Stick Charge 1. What causes static electricity? 2. Do all substances give rise to static electricity? 3. How long can charge be stored? 4. Does temperature affect how much charge is stored? NC Knowledge Identify common appliances that run on electricity. Working Scientifically Introduction to or reviewing the Planning process for scientific investigations. Using models to explain scientific phenomena. Recognise and apply Independent and Dependent variables. Develop and justify a prediction / hypothesis. Develop the ability to write a method. Recognise patterns in data and draw valid conclusions. Version /02/16 Page 8

10 Lessons 3 & 4: Introduction to Electrical Circuits Lesson 3: Teacher Demonstrations & Key Knowledge & Learning Objectives D3.1: SEP Energy board Learn that electricity requires a path called a circuit to flow around. Learn that if there is a break in a circuit then the electricity cannot flow. Learn that electrical circuits can be described using the analogy of water in pipes. Recognise different methods of electricity generation. Observe, describe and provide simple explanations of electrical energy transfers. Do all substances conduct electricity? Lesson 4: Children s Investigations & Key Questions I4.1: Electrical circuits circus. I4.2: Conducting and Non Conducting Materials 1. Does the number of components in a simple series circuit affect how they work? 2. Is there a relationship between the number of lamps and the brightness in a series circuit? 3. Does the number of cells in a circuit affect the loudness of a buzzer in a circuit? NC Knowledge Construct a simple series electrical circuit, identifying and naming its basic parts, including cells, wires, bulbs, switches and buzzers. Identify whether or not a lamp will light in a simple series circuit, based on whether or not the lamp is part of a complete loop with a battery. Recognise that a switch opens and closes a circuit and associate this with whether or not a lamp lights in a simple series circuit. Recognise some common conductors and insulators, and associate metals with being good conductors. Associate the brightness of a lamp or the volume of a buzzer with the number and voltage of cells used in the circuit. Compare and give reasons for variations in how components function, including the brightness of bulbs, the loudness of buzzers and the on/off position of switches. Use recognised symbols when representing a simple circuit in a diagram. Working Scientifically Identify use of evidence by scientists to develop ideas. Select appropriate ways of presenting scientific ideas. Learn how construct and draw a series of simple circuit diagrams with a variety of components. Discover how to create a range of different circuits and start to think about they may be applied. Version /02/16 Page 9

11 Lessons 5 & 6: Applications of Electrical Circuits - Alarming times! Lesson 5: Teacher Demonstrations & Key Knowledge & Learning Objectives D5.1: Buzz wire D5.2: Dynamo torch Review the fact a complete circuit is required for electrical devices to work. Apply simple circuit theory to explain the operation of a device in an unfamiliar context. Identify groups of people that would benefit from the development of dynamo torches. Recognise that a dynamo turned by hand can be used as an alternative to using batteries. Lesson 6: Children s Investigations & Key Questions I1: Building simple Burglar alarms. 1. Pupils link ideas from electrical circuits to applications in burglar alarms. 2. Pupils evaluated their designs and suggested ways to improve the alarm systems. NC Knowledge Identify common appliances that run on electricity. Construct a simple series electrical circuit, identifying and naming its basic parts, including cells, wires, bulbs, switches and buzzers. Use recognised symbols when representing a simple circuit in a diagram. Identify whether or not a lamp will light in a simple series circuit, based on whether or not the lamp is part of a complete loop with a battery. Recognise that a switch opens and closes a circuit and associate this with whether or not a lamp lights in a simple series circuit. Recognise some common conductors and insulators, and associate metals with being good conductors. Working Scientifically Define variables. Make and justify a prediction. Suggest equipment and method. Identify risks and how to act safely. Version /02/16 Page 10

12 Lessons 7 & 8: Magnetism from Electricity and Electricity from Magnets Lesson 7: Teacher Demonstrations & Key Knowledge & Learning Objectives D7.1: Oersteds discovery - Effect of electricity on compasses. 1. Learn that the flow of electricity is always associated with a magnetic field. 2. Learn that moving a magnet past atoms in a wire causes electrons to move and this is called electromagnetic induction. 3. Appreciate how Oersted and Faraday worked to undertake the discoveries of electromagnetism and electromagnetic induction. 4. Recognise that the size and direction of current flow in a wire affects the magnetic field produced by the wire. 5. Describe a negative consequence of our need for electricity. 6. Distinguish between opinion and scientific evidence about climate change. Lesson 8: Children s Investigations & Key Questions I8.1: Homopolar motors I8.2: Faraday Magnet torch 1. How can electricity and magnetism produce motion? 2. How does the movement of a magnet in a coil affect electricity produced? NC Knowledge 1. Identify common appliances that run on electricity. 2. Construct a simple series electrical circuit, identifying and naming its basic parts, including cells, wires, bulbs, switches and buzzers. 3. Identify whether or not a lamp will light in a simple series circuit, based on whether or not the lamp is part of a complete loop with a battery. 4. Recognise that a switch opens and closes a circuit and associate this with whether or not a lamp lights in a simple series circuit. 5. Recognise some common conductors and insulators, and associate metals with being good conductors. 6. Associate the brightness of a lamp or the volume of a buzzer with the number and voltage of cells used in the circuit. 7. Compare and give reasons for variations in how components function, including the brightness of bulbs, the loudness of buzzers and the on/off position of switches. 8. Use recognised symbols when representing a simple circuit in a diagram. Working Scientifically 1. Opportunities should be given throughout the lesson for children to use and develop their knowledge of planning investigations, through questioning and discussions on questions to investigate, making predictions and suggesting dependent and independent variables. Version /02/16 Page 11

13 Lessons 9 & 10: Magnetism and Electricity and Electricity Generation. Lesson 9: Teacher Demonstrations & Key Knowledge & Learning Objectives D9.1: DC Motor Learn where electricity comes from that is used in our homes and the wide variety of electricity generating stations. Appreciate the importance of finding non-polluting electricity generation now and for the future. Learn to describe in simple terms the operation of a DC motor (flowing electricity in a circuit creates a magnetic field that reacts against another one and moves away). Use scientific knowledge to suggest methods for increasing the strength of electromagnets. Identify a range of technological applications for Solar panels and wind generators. Start to appreciate the importance of developing alternative sources of electrical power other than coal, oil and gas. Conclusions drawn about the conditions needed to make the motor spin. Labelled schematic diagrams used to communicate ideas to explain the operation of motors. Explain how electric and magnetic effects are used to make motors. Lesson 10: Children s Investigations & Key Questions I10.1: Wind Generator I10.2: Solar Buggy 1. Solar panels are devices that convert solar or light energy into electrical energy. 2. Electrical energy from solar panels can be used directly or stored for use later to drive motors. 3. Wind can be used to spin a motor that will generate electrical energy that can be transformed into light, heat, movement etc NC Knowledge Identify common appliances that run on electricity. Construct a simple series electrical circuit, identifying and naming its basic parts, including cells, wires, bulbs, switches and buzzers. Identify whether or not a lamp will light in a simple series circuit, based on whether or not the lamp is part of a complete loop with a battery. Recognise that a switch opens and closes a circuit and associate this with whether or not a lamp lights in a simple series circuit. Recognise some common conductors and insulators, and associate metals with being good conductors. Associate the brightness of a lamp or the volume of a buzzer with the number and voltage of cells used in the circuit. Compare and give reasons for variations in how components function, including the brightness of bulbs, the loudness of buzzers and the on/off position of switches. Use recognised symbols when representing a simple circuit in a diagram. Working Scientifically In these last 2 experiments in the scheme, pupils will be working in groups of 5 or 6 to investigate a range of different variables and their impact on the amount of electricity generated by a wind powered generator and a solar buggy. Students will work as a team to identify a question that can be tested and should try to complete a full Investigation Plan that could be used as part of their final progress assessment. Version /02/16 Page 12

14 4. How does the orientation, quantity, shape and size of a propeller blade or quantity and or direction of wind affect the generation of electricity from a wind powered generator? 5. What are the key factors that affect how much electrical energy a solar cell can generate including charging time, distance and direction of light, type of light, power rating of a light source and do light filters affect the amount of charge generated? Teachers should check for sound understanding of good question formation, understanding of dependent and independent variables, forming predictions, justifying hypothesis, clear method writing including complete equipment lists and any research they may have undertaken and finally consideration of risk. Version /02/16 Page 13