Phys._219_Lec._10._2012.

# Phys._219_Lec._10._2012. - Lecture 10-1 Motional EMF Most...

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Lecture 10 Lecture 10 -1 Motional EMF Equilibrium is reached when E B Fq EF = = JG Ev B =− × G VE L v B L Δ= = G G Potential difference between the ends of rod More generally, ( ) L v B L = × G G GG induced emf L Most of the worlds electric energy is produced by electric generators, not by batteries. Motional emf is the principle behind the electric generator. Motional emf occurs whenever a conductor moves, cutting through magnetic fields. Assume that a conducting rod of length L moves with velocity in magnetic field . This creates a force on the conduction electrons in the rod. v G B G v ( ) B av F qv B G G G per electron on average accumulates conduction electrons near bottom. In response E develops, opposing the accumulation. B F G

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Lecture 10 Lecture 10 -2 Motional EMF of Sliding Conductor ¾ Magnitude of induced current I vBL I R R ε == ¾ Direction of current is as if the induced emf were due to a battery. Induced EMF counter-clockwise here vBL ε= Rod slides as before, but there is a complete circuit instead of a rod. • Induced emf moves electrons (current flows). • emf (and current) is maintained as long as the rod is sliding with v . ¾ Magnetic force F M acts on this I 22 M vB L FI L B R F M decelerates the bar (later: Lenz’s Law) + F M v G L
Lecture 10 Lecture 10 -3

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## This note was uploaded on 02/13/2012 for the course PHYS 219 taught by Professor Staff during the Spring '08 term at Purdue University.

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Phys._219_Lec._10._2012. - Lecture 10-1 Motional EMF Most...

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