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Transcript
IT’S ELECTRIFYING! A Facilitator's Guide to Electricity It’s Electrifying! Developed by Gillian Gerhard and Angelica Workman for Let’s Talk Science © 2002-2011 Let’s Talk Science Let’s Talk Science is an award-winning, national, charitable, science outreach organization. We deliver science learning programs and services that turn kids on to science, keep them engaged in lifelong learning and develop their potential to become 21st century stewards, innovators and citizens. Through our science outreach, we engage more than 2,700 enthusiastic postsecondary student volunteers at 33 universities and colleges across Canada to turn more than 110,000 children and youth on to science, engineering and technology each year. Our national science outreach is supported through donations, grants and the contributions of participating universities and colleges. Let’s Talk Science would like to thank our major science outreach supporters: If you believe, like us, that improving science literacy is fundamental for success in our rapidly changing world, please contact us to make a tax-deductible donation. Charitable Business Number: 88540 0846 RR0001 Let’s Talk Science National Office 1584 North Routledge Park London, Ontario, Canada N6H 5L6 t: 519.474.4081 tf: 1.877.474.4081 f: 519.474.4085 e: [email protected] url: letstalkscience.ca All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system without written permission from Let’s Talk Science. A. Description of Workshop Overview of Workshop Grade for Workshop/ Appropriate Age This activity is designed for use in Grade 4-6 classrooms or with children ages 9 to 12. Science Topics Electricity Magnetism Parallel and Series Circuits Conductors and Insulators Energy Sources Testing Materials Structural Strength Do electrons come out of both ends of a battery? Why won’t the bulb light? What’s a parallel circuit? Is wood a good conductor or an insulator? Students will explore these questions and more through fun, hands-on stations. Overall Objectives To familiarize students with a circuit. To demonstrate series and parallel circuits and discuss the differences. To learn about insulators and conductors To discover how electromagnets work. B. How to Run This Workshop Physical Requirements You will need a large classroom with a clear space big enough for all students to sit in a circle. You may need to set up stations. Materials and Set-Up Note: For more detail, see Kit List Activity #1 – Circuit Design Chicken Demonstration 12-15 zip-bags containing: *1, 1.5V C Cell 2 chirping chickens “Load and Source” signs “Electricity” signs 6” coated copper wire stripped at each end *1 bulb *It’s Electrifying Data Sheet (these get used up every workshop) 2 bean bags or tennis balls or ping pong balls (electrons) Activity #2 – Insulators and Conductors 4 zip-bags containing: Activity #3 – Parallel and Series Circuits Activity #4 Electromagnet 4 zip-bags containing: 3 wires with alligator clips on each end *1 bulb with holder 6 wires with alligator clips on each end *2 bulbs and holders 4 zip-bags containing: *4, 1.5V D Cells *1, 1.5V C Cell with holder *1, 1.5V C Cells with holders 1 m insulated wire with ends stripped 2 of each of following supplies: shoelaces, string, plastic ruler, metal ruler, wooden ruler, empty plastic cup (air), pipe cleaner, bendy straw, aluminium foil, pencil, balloon Insulators and Conductors Task Card Troubleshooting Card *Blank paper and pencils 20 + paper clips Parallel and Series Circuit Task Card 2 pairs of scissors Troubleshooting Card *Electrical tape or masking tape Electromagnets Task Card Extra blank paper for testing objects from around the class (optional) 1 galvanized nail *Consumable items (eventually – not after every workshop) Page 3 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science DELIVERY HINT: You can use the same zip-bags filled with materials for Activity #2 and Activity #3 if you are not setting up stations. You may just have to increase the number of zip-bags that you use. Timing of Activity Part of Workshop: General Introduction Activity #1 Chicken Demonstration Activity #2 Activity #3 Activity #4 Wrap-Up Suggested Timing: 5 min. 30 min. 15 min. 15 min. 15 min. 15 min. 10 min. Cumulative Timing: 5 min. 35 min. 50 min. 65 min. 80 min. 95 min. (OPTIONAL) 105 min. C. Introduction to Topic CHOICE: You can briefly ask the students what electricity is, why it’s important to us and where we get it from to start the workshop OR you can move right into Activity #1. D. Activities CHOICE: There are 4 activities and 1 demonstration for you to choose from. At lower grade levels (Gr. 4), leave out Activity #4 (Electromagnets) unless the class is very advanced. At higher grade levels, you will want to set up stations; at lower grade levels, you can go through the activities together. You choose the order of activities and where you fit in the demonstration. Page 4 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science ACTIVITY #1: CIRCUIT DESIGN (30 min.) It’s Electrifying Datasheets Objective of Activity To introduce circuits. To introduce the components of a circuit. Suggested Instructions, Q & A (Hand out worksheets and zip-bags ahead of time.) Some of you will already have discovered the worksheets and zip-bag on your desk. Working in groups of 2-3, see if you can come up with a way to make the light bulb light up using just the materials in the bag. You’ve got about 5 minutes, and in that time I would like you to draw on your worksheet a picture of how you’ve arranged the materials. Don’t worry if it doesn’t work the first time – we can learn as much from what doesn’t work as from what does. If you find an arrangement that makes the bulb light, draw the picture in the “bulb lights” box, and if you find an arrangement that doesn’t make the bulb light, draw that picture in the “bulb didn’t light” box. (This is your prior knowledge activity. Give the students 5 minutes depending on their level of prior experience with electricity and circuits. This should become obvious while watching them experiment. Stop them once a few groups have been successful – it’s not necessary for them to all have been successful. Encourage students who find one way to make the bulb light to find a different arrangement that also works. Encourage students who didn’t get the bulb to light to draw a picture of their circuit.) (Collect the bags of materials, retaining one for demonstrations.) Page 5 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science Discussion Did anyone get the bulb to light? Can someone volunteer to show us how you lit the bulb? Let's draw this on the board (all possible arrangements shown below.) + + - - + + - Did anyone discover a way to put the circuit together so that the bulb didn’t light? Can someone volunteer to show us how? Let's draw that on the board (possible arrangement shown below.) Page 6 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science Did anyone have a different arrangement to light the bulb? Did you make a picture of it on your sheet? How about a different way to not light the bulb? So there is more than one way to make a circuit. Let’s take a look at our two “circuit” drawings here. We’re going to examine at least 4 elements of our drawings. 1) SOURCE Battery (Draw a (1) on top of the cell in the “working” picture) Why do we need the battery? What does it do? It provides energy, power, electricity source. What kind of energy? Electricity. What is electricity? Current, stuff that runs lights and appliances, electrons and protons, charged particles, energy. Electricity is a form of energy consisting of charged particles. We generally think of the negatively charged particles or electrons. The electricity in our circuit here is current electricity, which means it’s moving. The electrons released by a chemical process in the battery flow, or move. That movement of electrons is the electricity. Where does electricity come from? Batteries, the wall, power plants (generated by: water, coal, nuclear energy, wind, gas, solar energy) So we need an energy SOURCE. (Write Source next to the cell) In this case it’s our battery. 2) CONDUCTOR Wire (Draw a (2) beside the wire on the “working” picture) What does the wire do? Why do we need the wire? It provides a medium in which the electrons can moves. It conducts the electricity. It moves the electricity from the source. Page 7 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science So we also need a CONDUCTOR for the energy. (Write CONDUCTOR on the board) Are wires the only things that will move electricity? Will it flow through anything else? Yes/No/Maybe What else could we use? Paperclip, wood, water Why does it flow through wires? What makes something a good conductor? They are made of: metal, steel, copper. What is special about metal? Why does it conduct electricity? What properties does it possess that make this possible? They can easily take electrons because their inner bits (their atoms) have room for electrons. BUT metals do NOT hold onto electrons very well, they don't like to keep them. When you pump electrons in, metal atoms give them away to each other...causing a FLOW of electrons through the metal (Just like Hot Potato – something that conducts electricity well plays the hot-potato game with electrons well. Taking them and passing them along quickly.) What is the opposite of conducting? If conductors take electrons and pass them on, then what would the OPPOSITE of a conductor do? They might take electrons and not pass them on or just not take the electrons at all. This is called an insulator. What do you think a good description of an insulator would be? Insulators do not have room in their atoms for extra electrons so they don't want to take any new ones on. BUT sometimes they do accept electrons, when this happens they hold onto to them very tightly, not wanting to give them away. Electrons do NOT flow easily through insulators. (For the hot potato analogy, an insulator might have its hands full so it can’t take the potato.) Give me some examples of materials that conduct electricity. Metal Page 8 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science Give me some examples of insulators. Plastic, rubber, fibre glass insulation, glass One of the activities you will do during today's session is to test your hypotheses about which materials conduct electricity and which materials insulate. So, we’ve got a source and a conductor. What happens if there is no light bulb? Alone, the flow of electricity through a wire just produces a hot wire and a worn out battery. We want to make use of that flowing electron phenomenon to do something. Can you think of anything useful that uses electricity? lights, computers, toaster, radio, …. So, back to our circuit, we need a load - something that uses the electricity. That’s where the light bulb comes in. 3) LOAD Light bulb (Draw a (3) beside the light bulb on the “working” picture) Does anyone know how the light bulb uses the flow of electrons? The electrons flow into the side of the bulb, through the filament and out the bottom into the positive terminal of the battery. Why does the filament glow when electrons go through it? The filament is not a good conductor. It has many imperfections that cause resistance to the movement of the electrons. This increases COLLISIONS, producing heat. The heat makes the filament glow. The other diagram (of a set up that did not light the bulb) has all 3 critical parts. Why didn’t the bulb light? Need another wire, need to connect them What would you do with the other wire, how would you connect them? Does someone want to come up and draw it? Page 9 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science (Make sure one wire connects to the side of the bulb and another at the very tip of the bulb) We need to make a closed circle. That’s the fourth critical part of our circuit. 4) CIRCUIT What do I mean by a circuit? The drawing, the arrangement. A circuit actually refers to a closed loop around which electrons can flow. It has to be present for everything to work. If it isn’t closed, the electrons won’t flow … no electricity (= open circuit!) Does anyone know which way the electrons are flowing around this circuit? positive to negative, negative to positive, both ways, … ELECTRONS WILL ONLY FLOW FROM NEGATIVE TO POSITIVE!!! Who has heard the rule: Opposites attract? What does it mean in magnets? North is attracted to South In electricity we talk about positive and negative charges. Electrons are NEGATIVELY charged. They want to move to the positive terminal of the battery. SO...they flow out the negative end, around a circuit and into the positive end. BUT only if it senses the positive "pull". It won't move unless it is attracted by the positive. That means the circuit needs to be closed. Page 10 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science CHICKEN DEMONSTRATION (15 min.) Use Signs – Electricity, Load, Cell Suggested Instructions, Q & A We are going to be a circuit, and this is going to require cooperation. Form a tight circle sitting or standing in an open area in the classroom. DELIVERY HINT: This works best if the children are not sitting on a rug and no one is touching metal. What are the four parts that we need? (Hand out cards) 1. A source, a dry cell. (one student will be the ‘cell’) 2. Wire, a conductor (most students sitting in the circle are ‘wires’) 3. A load, an electrical appliance (like a CD player or school bell) (one student will be the ‘load’ and will have to make a noise whenever they receive an electron, and stop when they don’t have an electron in hand.) 4. A closed circuit. (the circuit is closed if all the students’ ‘wires’ (knees) are touching. The ‘cell’ needs to make sure this is happening before sending out an electron, and one ‘wire’ cannot pass an electron to another if the circuit isn’t closed.) There are some interesting things about ‘wires’ – they’re really quiet! And ‘loads’ don’t work unless they have electrons flowing through them. So, ‘loads’, you shouldn’t be making any noise unless you have electrons. (Hand out two ‘electrons’ to the ‘cell’. The ‘cell’ will start the flow of ‘electrons’ around the closed circuit. Remind students that the electrons must start and end at the ‘source’. Remind ‘source’ that the electrons won’t flow unless the circuit is closed – they need to confirm this. Remind students that the ‘wires’ are conductors – like the hot potato game. Take the ‘electron’ and pass it along. When the ‘load’ gets the electron he/she should make a sound, and stop when they give the ‘electron’ away. Let the ‘electrons’ go around the circuit once or twice.) Page 11 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science (Watch for teachable moments here – breaks in the circuit (electron flow should stop), electrons flowing out of both hands of the ‘cell’ (positive and negative), students noticing that their load only makes beep-beep sounds not continuous noise, but their CD player makes continuous sound – this is because real electrons move at close to the speed of light. You can try adding more ‘electrons’ in to the circuit to make the sound more continuous.) (Once they get the concepts, remove the ‘electrons’ and the component cards and introduce the chicken. ) I’ve got a little chicken here that contains both the source and the load in the same fuzzy yellow box. Let’s replace our ‘cell’ and electrical devices with this chicken and see if we really can be conductors. The chickens are Easter toys that contain a battery and a chirping mechanism. When we touch both of the terminals on the bottom of the chicken, a circuit is completed and the chicken starts to chirp. When we stop touching one or both of the terminals, the chicken stops chirping. (Students hold hands and one at each end of the circle connects to the chicken terminal. Watch what happens when one person breaks contact.) DELIVERY HINT: Students cannot be touching anywhere else (i.e. at the knees) or anything else (i.e. desks) for this to work. Also, if girls and boys are making a fuss about holding hands, they can touch pinkies instead. Let’s introduce a second chicken into our circuit (again with its own cell and load.) (Have students next to the first chicken connect to the second chicken terminals.) Notice that I’ve put these two chickens into our circuit IN SERIES - that is one after another. What happens if we break the connection at one of the chickens? Does the other keep chirping? Why not? (see on diagram) Page 12 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science The chickens stop chirping because the circuit is broken – the electrons can’t get back to their own positive terminal. (Draw a diagram of this circuit on the board.) Can anyone think of a way we could rearrange this human/chicken circuit so that if we broke the connection at the first chicken, the second would keep on chirping? (Move some of the students, including the second chicken, into or outside of the circle. Close the original circle and check that the first chicken chirps. Have the students near the second chicken form a wire running parallel to the first chicken and tap into the circle.) Notice that we’ve now put these two chickens IN PARALLEL to one another (like lights in this classroom – if one goes out, they don’t all go out), that is one beside the other, each with their own wires running to the circle. Both chickens should chirp. What are the electrons doing in this circuit? Since both chickens are the same, some of the electrons are going through chicken one and others through chicken two. (See what happens when you break the connection at the first chicken but between the “tap into the circle” people from the second chicken.) (see on diagram) Chickens 2 2 1 1 Break Here Series Parallel Page 13 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science Chicken two should keep on chirping, but chicken one should stop. What are the electrons doing now? Where are they going? See what happens when you break the circuit outside of the “tap into the circuit” people) (see on diagram) Chicken one should chirp, but chicken two should not. (Draw a diagram of this circuit.) (See what happens if you take chicken two completely out of the parallel circuit, but leave the people/wire there with a gap where chicken two was.) Chicken one should keep chirping. (Have students go back to their desks.) ACTIVITY #2: INSULATORS AND CONDUCTORS (15 min.) Use Insulators and Conductors Task Card Objective of Activity To test various materials to determine whether they are insulators or conductors of electricity. Suggested Instructions, Q & A (Go over Task Card instructions with entire group. Point out where they should fill in information on the Data Sheet. Remind them that there may be a Troubleshooting Card at the activity – read it if they have problems!) Page 14 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science ACTIVITY #3: PARALLEL AND SERIES CIRCUITS Use Parallel and Series Circuit Task Cards Objective of Activity To design parallel and series circuits and learn the difference between the two. Suggested Instructions, Q & A (Go over Task Card instructions with entire group. Point out where they should fill in information on the Data Sheet. Remind them that there may be a Troubleshooting Card at the activity – read it if they have problems!) ACTIVITY #4: ELECTROMAGNETS Use Electromagnets Task Card Objective of Activity To create an electromagnet and manipulate the strength of the magnet by changing the number of coils and/or the number of batteries used. Suggested Instructions, Q & A (Go over Task Card instructions with entire group. Point out where they should fill in information on the Data Sheet. ) Page 15 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science E. Wrap-Up When you tested the insulators and conductors, did anyone find any surprises? Was there anything you thought would conduct and didn’t? Anything that you thought would insulate that conducted? When you were making your parallel and series cirucits, did anyone get both bulbs to light? Get your series circuit to work? Did you draw it? How about the parallel series? Did you draw it? (The students can draw their circuits on the board. Make sure everyone uses the same symbols to represent source, load, conductor… ) Did anyone magnetize their nail? Did you make your electromagnet stronger? How? Does anyone have ideas about how it works? The current flowing through the wire induces a magnetic field in the metal nail – lining up its poles and turning it into a temporary magnet. Magnetic fields develop perpendicular to electric fields, so we wrap the wire around the nail to get the current flowing around the nail and the magnetic field aligned along the nail. That field is only present as long as the current is flowing. You can make the field stronger by increasing the amount of current. We do this either by increasing the amount of coils (sort of like increasing the electric surface area) or by increasing the amount of current going through those coils (by adding more batteries.) What was your favourite activity today? Do you think Science is fun? Do you like Science? Do you have any questions for me? Page 16 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science F. Glossary Ammeter An instrument used to measure the amount of electric current flowing through a particular point in an electrical circuit. Battery One or more cells in series. Cell An electrochemical device that converts chemical energy into electrical energy. Circuit The complete path of an electric current. An open circuit does not allow current to flow, a closed circuit does. Conductor A material through which electrons can flow. Electric Current A flow of electric charge through a conductor. Electricity A form of energy, consisting of oppositely charged particles, that can produce light, heat, magnetism and chemical change; and which can be generated by friction, induction or chemical change. Electromagnet A temporary magnet produced by an electric field. Electrons These are negatively charged particles found orbiting the nucleus of an atom. Since electrons are negatively charged, they are attracted to positive charges and flow from negative to positive. Insulator A material which allows no electrons (or very few) to pass through. Page 17 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science Parallel Circuit A circuit that is formed when the components are arranged so that there is more than one path for the current to take. like terminals + _ _ Resistance Is caused by structural "imperfections" in a material that cause electrons to collide with them; it slows down the flow of charges. Series Circuit A circuit that is formed when the components are arranged so that there is a single path for the current to take. + _ Voltmeter An instrument used to measure the potential difference between any two points in an electrical circuit. Page 18 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science G. Suggested Resources Websites What is Static Electricity? http://www.sciencemadesimple.com/static.html The Minds that Discovered Electricity http://www.outlawnet.com/~oclass/electricity/founders.html Canada Science and Technology Museum http://www.science-tech.nmstc.ca/english/schoolzone/Info_Electricity.cfm Page 19 of 20 In-class workshops, It’s Electrifying! ©2002 Let’s Talk Science