lecture11 - Generators and Transformers Physics 102:...

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Unformatted text preview: Generators and Transformers Physics 102: Lecture 11 V e r i f y ‘ E X ’ g r a d e s f o r E x a m # 1 ! Review: Magnetic Flux φ is angle between normal and B B A φ n o r m a l Φ = B A cos( φ29 Units is T m 2 = Wb Review: Induction • Faraday’s Law – Magnitude of induced EMF given by: • Lenz’s Law – If the magnetic flux ( Φ B ) through a loop changes, an EMF will be created in the loop to oppose the change in flux – EMF current (V=IR) additional B-field. • Flux decreasing => B-field in same direction as original • Flux increasing => B-field in opposite direction of original 7 i f i f t t t- Φ- Φ- = ∆ ∆Φ- = ε Review: Rotation Variables v, ϖ , f , T • Velocity (v): – How fast a point moves. – Units: usually m/s • Angular Frequency ( ϖ ): – How fast something rotates. – Units: radians / sec ϖ r v v ϖ = v / r f = ϖ / 2 π T = 1 / f = 2 π / ϖ • Frequency ( f ): – How fast something rotates. – Units: rotations / sec = Hz • Period (T): – How much time one full rotation takes. – Units: usually seconds 10 Generators and EMF ε loop = ϖ B A sin( ϖ t) Φ = BA cos( ϖ t) v v • x θ ϖ r 1 2 13 ε t ϖ AB-ϖ AB EMF is voltage! Φ = B A cos( θ ) = B A cos( ϖ t) ε loop = - ∆Φ / ∆ t = ϖ B A sin( θ ) = ϖ B A sin( ϖ t ) Generators and EMF v v • x θ ϖ r 1 2 13 ε t ϖ AB-ϖ AB EMF is voltage!...
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This note was uploaded on 01/25/2012 for the course PHYS 102 taught by Professor Lee during the Spring '08 term at University of Illinois, Urbana Champaign.

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lecture11 - Generators and Transformers Physics 102:...

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