lecture23 - Magnetic Induction Magnetic magneticflux...

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Magnetic Induction Magnetic Induction - magnetic flux - induced emf  - Faraday’s Law and Lenz’s Law
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Magnetic Flux Magnetic Flux Flux through a surface S:      B = Φ S dA B - a scalar ;  units,  1 T∙m = 1 Weber (Wb) - represents “number of magnetic field lines through a surface S” ( dA  is the “area vector”, perpendicular to the surface.)  
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Magnetic Flux Magnetic Flux Flux through a  closed surface S:      0 dA B = S This is like Gauss’ law, but for magnetism.  However, it states that: - the number of magnetic field lines that enter a  volume enclosed by a  surface S  must equal the number that leave the volume - and it implies that magnetic monopoles do not exist
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Faraday’s Law: Faraday’s Law: When the  external magnetic flux   Φ B through a closed conducting loop  with one turn  changes , the emf induced in the closed loop is: dt d B Φ - = ε (for a loop with  N turns:     ) dt d N B Φ - =   Note that  Φ B  changes if: 1)  B  changes 2) the area  of the circuit changes ( dA ) 3) the orientation  of the circuit changes ( B•dA ) ( 29 θ cos BA dt d - =
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Lenz’s Law (the negative sign) Lenz’s Law (the negative sign) (for the direction  of the induced emf)  The induced emf and induced current direction in the loop is  such that the magnetic flux it produces inside the loop 
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This note was uploaded on 10/14/2011 for the course ENGINEER CHEM ENG 3 taught by Professor Ghosh during the Spring '11 term at McMaster University.

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lecture23 - Magnetic Induction Magnetic magneticflux...

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