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Electromagnetic Induction Group: Induction Wong Chun Jie Leong Qi Dong Jwa Li Wen 4S2 2012 T3

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Introduction Current flowing through a conductor produces a magnetic field Can a magnetic field produce a current in a conductor?

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Video http://www.youtube.com/watch?v=ITuR3AQA YI8 http://www.youtube.com/watch?v=ITuR3AQA YI8 1:07:50 – 1:10:4`

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Theory – Electromotive Force (emf) A varying magnetic flux produced an e.m.f, which produces an induced current in a closed circuit.

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Faraday’s Solenoid Experiment

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Steps 1. Move magnet into solenoid 2. Leave the magnet in solenoid 3. Move magnet out of solenoid

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Variables Dependent: (1) Deflection of galvanometer pointer (2) Direction of deflection (3) Magnitude of deflection Independent: Pole of magnet Number of turns in solenoid Strength of magnet Cross-sectional area of solenoid Speed of magnet being moved in and out

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Results (1) Deflection of galvanometer pointer Deflects: magnet is moving in and out of solenoid Does not deflect: magnet remains stationary in solenoid Current is flowing through circuit only when the magnet is moving in and out of the solenoid

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Conclusion A varying magnetic field produces an e.m.f, which produces an induced current in a closed circuit.

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Results (2) Direction of deflection Action of Bar Magnet Direction of Deflection Direction of e.m.f N-pole insertedRightAnti-clockwise N-pole withdrawnLeftClockwise S-pole insertedLeftClockwise S-pole withdrawnRightAnti-clockwise

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Conclusion Lenz’s Law The direction of the induced emf, and thus, the induced current in a closed circuit, is always such that the magnetic effect always opposes the change producing it. Why oppose? – In Work, Energy, Power: GPE = KE – In Electromagnetic Induction: GPE = KE + Electrical energy – KE decreases for the conservation of energy

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Results (3) Magnitude of deflection Increase in number of turns in solenoid strength of magnet cross-sectional area of solenoid speed of magnet being moved in and out Increases deflection – increases emf N Φ B Rate

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Conclusion Faraday’s Law of Induction Where ℰ is the emf Induced emf generated in a conductor is proportional to the rate of change of magnetic flux vector linking the circuit.

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References http://physics.tutorvista.com/electricity-and- magnetism.html#close_iframe http://physics.tutorvista.com/electricity-and- magnetism.html#close_iframe http://en.wikipedia.org/wiki/Faraday's_law_of _induction http://en.wikipedia.org/wiki/Faraday's_law_of _induction http://en.wikipedia.org/wiki/Magnetic_flux http://en.wikipedia.org/wiki/Electromotive_fo rce http://en.wikipedia.org/wiki/Electromotive_fo rce

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Thank You

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