How Does Changing Resistance Affect Induced Current Direction in Nested Loops?

AI Thread Summary
Increasing the resistance in the larger loop causes a decrease in current, leading to a decreasing magnetic field. According to Lenz's law, the induced current in the smaller loop will flow counterclockwise to oppose this change. For the small loop placed outside the larger one, the magnetic field direction just outside the larger loop is crucial; it points into the page, resulting in a clockwise induced current in the small loop. The confusion arises from the position of the small loop, as its response to the changing magnetic field differs based on its location relative to the larger loop. Understanding the flux change through the small loop is key to determining the direction of the induced current.
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Homework Statement



(a) If the resistance of the resistor in the figure below is slowly increased, what is the direction of the current induced in the small circular loop inside the larger loop?
(b) What would it be if the small loop were placed outside the larger one, to the left?

c0826c28da63693ccf1b08caed5fae05.jpg


Homework Equations



V = IR
E (emf) = d(flux)/dt
flux = B(perp.) * A

The Attempt at a Solution



I know we have to use the right hand rule, but I think I must be doing it wrong.

For a, we know that B must be decreasing becase I is decreasing (and B = u(o) * I(encl.)/dl)

According to Lentz's law, if the flux(B*A) is decreasing then the induced current will have the same field as the other. So in order for both fields to be pointing out as they are, the current must go in the counterclockwise direction in the inner loop.

for part b though, I use the right hand rule and get the same thing-counterclockwishe? But the answer says its clockwise. I don't understand. The flux of the large loop is still decreasing, so doesn't that mean the fields again point in the same direction? That would be both pointing outward. If I use my RHR that I know, in order for the B field to be pointing in the same direction of the induced current, it must go counterclockwise.

Is there something to be said for the fact that it is outside of the loop?

Thanks!
 
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What matters is the flux through the small loop and how it is changing. In what direction does the field point just outside and to the left of the big loop? (That's where the small loop would be for part b.) How is it changing?
 
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