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Faraday's law of induction

1. Homework Statement

attachment.php?attachmentid=34851&stc=1&d=1303698759.jpg

#32
2. Homework Equations

faraday's law of induction


3. The Attempt at a Solution
umm i dont really understand this concept:frown: so heres my attempt. the answer is C so is it because if you have a wire within a wire and the current of one wire is going one direction, the current of the other wire always goes the opposite direction?
 

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No that is not a good way to think about it. If the current in the outer wire were decreasing, then they would be going the same way. You have to think in terms of flux. Lenz's law says: "An induced current is always in such a direction as to oppose the motion or change causing it"

The cause of the induced current is the changing magnetic flux through the loop. The flux is increasing into the page, so the wire on the inside needs to produce a flux out of the page to resist the change.

If the wire on the outside had its current decreasing then there would be less flux into the page, so the inside wire would have to produce more flux into the page, and the currents would be in the same direction.
 
thxthx i understand it now ^^
 
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oh cool my teacher showed us this in class too! lool
 

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