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

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SUMMARY

The discussion centers on the effects of changing resistance on the direction of induced current in nested loops, specifically addressing two scenarios: one where the small loop is inside the larger loop and another where it is outside. In the first scenario, as resistance increases, the induced current in the small loop flows counterclockwise due to a decreasing magnetic field, in accordance with Lenz's Law. In the second scenario, despite the decreasing flux, the induced current in the small loop placed outside the larger loop flows clockwise, as the magnetic field direction changes based on its position relative to the larger loop.

PREREQUISITES
  • Understanding of Lenz's Law
  • Familiarity with the Right Hand Rule (RHR)
  • Knowledge of electromagnetic flux and its calculation
  • Basic principles of inductance and current direction
NEXT STEPS
  • Study the application of Lenz's Law in various electromagnetic scenarios
  • Explore the Right Hand Rule in more complex configurations
  • Investigate the relationship between resistance changes and induced electromotive force (emf)
  • Learn about magnetic field lines and their interaction with current-carrying loops
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Physics students, educators, and anyone interested in understanding electromagnetic induction and its practical applications in circuit design and analysis.

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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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