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Transcript
60 minute physics Nine hands-on activities: with GCSE Physics curriculum links Electric circuits Mapping data Digital Electric circuits Machines & electromagnets Flight & movement Light Storing energy Forces & motion Changing states Electric circuits STEM engagement materials developed for the Royal Air Force Electric circuits This activity forms part of a suite of physics-related activities developed by West Yorkshire STEM in collaboration with the University of Leeds. They have been funded by the Royal Air Force to encourage pupils to think positively about STEM generally and physics in particular. Each activity has been designed to be interactive and linked to GCSE physics specifications of OCR and AQA. Stretch or extension activities are provided in the content for additional follow-up beyond the session. Electric circuits To run this activity you will need: •A flat teaching space with enough room for small groups (of around 4 pupils) to work together to work through activities. •Powerpoint facilities to introduce the content and activities (using ‘Electric_circuits.pptx’). •1 copy of the handout ‘Making speakers.pdf’ per student. (for building speakers) •1 Double ended audio jack, cut in half per student. •1 10mm diameter, 5mm height Neodymium magnet per student. •1 5cm width, 30 cm length of scrap paper per student. •1 Plastic or Styrofoam cup per student. •1 10m of 0.15mm diameter enamel coated copper wire per student. •1 Multimeter or Ohmeter per class. •5 Hot glue guns and glue gun sticks per class. •10 pairs of scissors per class. •10 Rolls of electrical tape per class. •20 sheets of very fine sand paper per class. •1 ‘Certificate of completion’ for each student - produced as part of these materials (Certificate_electric_circuits.pdf) Level: KS3/KS4 GCSE science curriculum links: electricity / electromagnetism Objectives of the session •Understand electrical potential and how current flows around a circuit •Understand electromagnetism •Demonstrate knowledge of how speakers employ electricity to function Session length: 60 mins Session overview •Presentation (20 mins) •Building speakers (40 mins) Extension: Teaching Advanced Physics (TAP): electric current This online resource looks at basic electrical ideas, particularly current, potential difference and energy. It has been developed and produced by the Institute of Physics and is available at: http://tap.iop.org/electricity/current/index.html. 2 Slide 1 Introduction to the session •Introduce yourself as the facilitator and outline (briefly) your STEM background. •Ask STEM Ambassadors (if present) to (briefly) introduce themselves and to say which STEM discipline/industry they are from. Slide 2 Gravitational fields •Mass ‘M’ has gravitational field ‘G’ •‘Gravitational’ means that the field is due to gravity •All ‘masses’ have gravitational fields, people have gravitational fields, atoms have gravitational fields, but the ‘magnitude’ or ‘how big ‘ the gravitational field is depends on how big the mass is •A good example of a large mass is the earth, it has a gravitational field that pulls the moon towards it •A gravitational field is illustrated by ‘field lines’, direction of pull is denoted by arrows •A gravitational field exists only because mass ‘M’ exists – this is an important point •For all field lines, the closer they are together, the greater the force of the field •d1 shows a smaller distance between the field lines than d2, so the force of the field is larger closer to mass ‘M’ •This is shown is the second diagram, the force exists all around mass ‘M’, the darker green is a stronger force field and the lighter green is the weaker force field. Slide 3 Electric fields •In an atom, we have three things: protons (positively charged), neutrons (neutrally charged) and electrons (negatively charged) •An electric field only exists around things that are ‘charged’ •So in an atom, the things that have a ‘charge’ are protons and electrons •The electric field only exists because there is a charge present (whether it’s positive or negative) •Protons have a repelling electric field while electrons have an attractive electric field, just like the gravitational field. 3 Slide 4 Magnetic fields •Here we have a diagram of a wire that is full atoms that have both positive and negative charges •Like every charge has an electric field, every moving charge has a magnetic field •Magnetic fields only exist because there is a moving charge, specifically, electrons moving through the wire •The magnetic field produced ‘wraps’ around the wire, and we’ll learn how this happens in the next few slides. Slide 5 Permanent magnets •All permanent magnets have a north and south pole, and the magnetic fields are illustrated, one again, using field lines •The magnetic field goes from the north to the south pole Slide 6 Permanent magnets (continued) •We can visualize the magnetic field when we place iron filings around a magnetic, we can see the fields going from the north to the south pole. 4 Slide 7 Magnetic field in an electric coil •If we create a coil out of many wire loops stacked on top of each other, and send current through the coil, you get a lot of magnetic field around the wire •The magnetic field of all the loops add up together, and you get a magnetic field that looks very much like a field around a bar magnet •We get a north pole and a south pole around the coil, creating an electromagnet: a magnet created using an electric current •The more loops we have the stronger the magnetic field. Slide 8 How speakers work •The job of a speaker is to convert electrical signal from the sound source into an audible sound: we start out with a permanent magnet with a north and south pole. Slide 9 and 10 How speakers work (continued) •We then create an electromagnetic coil around the permanent magnet, which has its own magnetic field around it with a north and south pole when current flows through the wire. The permanent magnet is fixed, but the electromagnet can move. •This coil behaves like a normal permanent magnet but with one handy property: when the flow of current reverses direction, the poles on the magnet flip – where the north pole becomes south and vice versa. •As pulses of electricity pass through the coil, the direction of the magnetic fields rapidly change and the poles of the electromagnet switch. This means that electromagnet is attracted and repelled from the permanent magnet and vibrates back and forth. •The electromagnet is attached to a diaphragm or cone that amplifies these vibrations, pumping sound waves into the surrounding air and towards your ears. 5 Slide 11 Let’s make a speaker •Provide pupils with a copy of the handout: ‘Making speakers.pdf’ Slide 12 Steps to assemble speaker 1 •(1) Stick magnet to the inside-bottom of the cup. •(2) Wrap copper wire coil and stick to outside-bottom of cup. •(3) Join copper wire to audio jack. Slide 13 Steps to assemble speaker 2 •(1) Stick magnet to the bottom of the cup. •(2) Wrap copper wire coil and stick to outside-bottom of cup. •(3) Join copper wire to audio jack. 6 Slide 14 Steps to assemble speaker 3 •Stick magnet to the bottom of the cup. •Wrap copper wire coil around paper tube & hot glue around magnet. •Join copper wire to audio jack. Slide 15 Steps to assemble speaker 5 •(1) Stick magnet to the inside-bottom of the cup. •(2) Wrap copper wire coil and stick to outside-bottom of cup. •(3) Sand ends of copper wire & join to audio jack. •(4) Now test your speaker! Slide 16 RAF examples: electromagnets •Using electromagnets isn’t something new. The RAF were using them a long time ago. •Look at this example of a magnet fitted to an aircraft. •It was used the detect mines during the Second World War. 7