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# Magnetic fields and electromagnetic induction

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### Magnetic fields and electromagnetic induction

1. 1. Magnetic Fields and Electromagnetic induction A2 topic
2. 2. Today’s lesson • How can we measure the strength of a magnetic field? • Upon what factors does the magnitude of the force on a current- carrying wire depend? • How is the direction of the force found for a current-carrying wire in a magnetic field?
3. 3. What is magnetism? Electrostatic repulsion is the force that stops you falling through the floor. Normally this force acts at the nanometre level. Magnetism is when the electrons have been lined up and work together. The classical view is to see all the electrons moved to one end of the magnet, creating an unbalance. However this does not happen http://www.youtube.com/watch?v=wMFPe-DwULM
4. 4. Magnets and magnetic fields Important facts 1)Magnetic fields have 2 poles (North, South). 2) The magnetic metals are iron, nickel, cobalt. 3)The magnetic field is most dense at the poles. 4)Magnetic field lines go from the North to South. 5)The Earth has a magnetic field. 6)Current flowing through a wire creates a magnetic field.
5. 5. Magnetic Fields Use the iron filings in the Petri dishes to see the magnetic field lines of a bar magnet. Try and see the magnetic field of a wire, you may have to loop the wire around a pencil a few times (caution hot!) Use a heatproof mat
6. 6. How can we measure the strength of a magnetic field? • Hall probes varies its output voltage in response to changes in magnetic field. • B is the letter used for the magnetic field (B-field) • The tesla (symbol T) is the SI derived unit of magnetic field B Hall probes are used to check timings of pistons in car.
7. 7. Upon what factors does the magnitude of the force on a current-carrying wire depend?