L30_a - FARADAYS LAW OF INDUCTION (Chapter 23) Look at a...

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Unformatted text preview: FARADAYS LAW OF INDUCTION (Chapter 23) Look at a conductor moving ACROSS magnetic field lines Free electrons move perpendicular to B r (into page) o Electrons (neg.) feel force B v e F r r r = Force on electrons is down o Result is potential difference induced between ends of bar bottom more negative CONCLUSION: potential difference can be induced across a conductor moving through a magnetic field Will come back to this example later when we have more theory v F B in SOME DEMONSTRATIONS: A magnet moving into/out of a loop of wire induces a current o See fig. 23.2 in text Starting/stopping current through loop in one coil (primary) causes pulse of current in coil (secondary) linked by iron coil - this is a transformer o See fig. 23.3 in text FARADAYS CONCLUSION from observations like these: Time-varying magnetic fields can induce currents To quantify, need to relate induced potential difference to changing magnetic flux Ammeter N S Ammeter primary secondary iron switch battery MAGNETIC FLUX: proportional to number of magnetic field lines through area area element A d r : vector perpendicular to area element contribution to magnetic flux from A d r is A d B r r Total flux through area is = area B A d B r r Unit for flux is T m 2 Wb (1 Weber) emf symbol is Work to push unit charge through a wire (or space) Units of emf are volts originally electromotive force BUT not a force: long name no longer used If resistance in loop is R, then current in loop is R I / = dA B Battery is source of emf FARADAYS LAW OF INDUCTION...
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This note was uploaded on 03/08/2012 for the course PHYSICS 1051 taught by Professor Michaelmorrow during the Winter '12 term at Memorial University.

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L30_a - FARADAYS LAW OF INDUCTION (Chapter 23) Look at a...

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