Lenz's law - magnetic fields and Currents

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Discussion Overview

The discussion revolves around Lenz's law, specifically examining the behavior of currents in different situations involving changing magnetic fields. Participants explore the relationship between magnetic flux and induced currents in various scenarios, aiming to clarify their understanding of the law's implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about why the current in situation B is as high as in situation A, despite differing conditions.
  • Another participant emphasizes the importance of considering the direction of the magnetic field in each half of the loop when analyzing the currents.
  • A participant suggests that the decreasing part of the magnetic field should lead to a lower current in situation B, proposing that it might be half of A.
  • Another participant counters this by stating that the change in magnetic flux through each half of the loop is what matters, prompting further analysis of the direction of the magnetic field and the change in flux.
  • A later reply confirms that since the change in flux in situation B is equal to that in situation A, the magnitudes of the currents must also be equal.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasoning behind the equality of currents in situations A and B, as some express confusion while others provide explanations. The discussion remains unresolved regarding the implications of the magnetic field directions and their effects on current magnitudes.

Contextual Notes

Participants reference specific scenarios and conditions without fully resolving the mathematical implications or assumptions underlying their arguments. The discussion highlights the complexity of interpreting Lenz's law in different contexts.

kidi3
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Hey Pf..

I am trying to understand Lenz's law, but somehow it doesn't make sense.
In my book there is some checkpoints execise to test wheather you've understood what you read about, one those checkpoints looks like this.

http://snag.gy/NCNLh.jpg


I do understand why the current in situation a is the highest since the magnetic field is increasing will it never become zero, and in situation C will the current decrease until become constant (B=0)=> current =0.
But why should the current in situation B be as high as in situation A.. ?
 
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kidi3 said:
But why should the current in situation B be as high as in situation A.. ?
Take note of the direction of the magnetic field in each half of the loop.
 
It's both in and out.. but wouldn't the dec. part go to 0, and lead the B to become ½A..
I can see B would be as high as A in a short moment,should it not be ½A thereby lead B<A
 
kidi3 said:
It's both in and out.. but wouldn't the dec. part go to 0, and lead the B to become ½A..
No.

What matters is the change in the flux through each half of the loop.

In the top half (of B) which way does the field point? Since it's increasing, which way is the change in flux pointing?

Same question for the bottom half. Which way does the field point? Since it's decreasing, which way is the change in flux pointing?
 
Ah.. they all point in the same direction, and since change is equal to the one in situation A, they must be equal in magnitude..
 
kidi3 said:
Ah.. they all point in the same direction, and since change is equal to the one in situation A, they must be equal in magnitude..
Exactly. The change in flux through each half of B points in the same direction, just like it does in A.
 

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