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Electro magnetic Induction problem. Simple one, but check wehre I am wrong. 
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#1
Feb2607, 12:18 AM

P: 239

1. The problem statement, all variables and given/known data
A magnet moving down, goes through a coil and exits it below. Plot the graph showing variation of induced emf in coil with time. 2. Relevant equations emf =  Flux/Time 3. The attempt at a solution As the magnetic field B increases, emf becomes more and more negative. Then while leaving, B decreases, emf becomes more and more positive. Hence The emf is first negative, forms a V shape in the negative emf region and then an inverted V in the positive emf region when it leaves. 4.Answer in the textbook The emf is first positive ... in other words just the opposite of what I said. Where did I go wrong ? 


#2
Feb2607, 09:47 AM

P: 464

From what two points are you measuring the emf?



#3
Feb2607, 10:26 PM

P: 239

From either ends of the coil



#4
Feb2707, 01:17 AM

P: 7

Electro magnetic Induction problem. Simple one, but check wehre I am wrong.
Isn't the "B" in this system a vector?
(Those tricky vectors...) ~A137 


#5
Feb2707, 02:13 AM

P: 239

Ya. But how will that matter?



#6
Feb2707, 02:32 AM

P: 239

I think I get it now.
Initially B and Area vectors are antiparallel, so flux is negative. Hence, the induced emf is positive. 


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