What Direction Does the Induced Current Flow When a Magnetic Field Decreases?

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Discussion Overview

The discussion revolves around the direction of the induced current in a wire loop when a magnetic field passing through it decreases over time. Participants explore the implications of Lenz's law and Faraday's law of induction, focusing on the theoretical understanding of induced currents in electromagnetic contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the induced current should flow counterclockwise to generate a magnetic field that opposes the decrease in the original magnetic field, as per Lenz's law.
  • Others express confusion about why the induced current must minimize the change within the loop rather than outside, suggesting that if the fingers of the right-hand rule point out of the page, the current would flow clockwise.
  • A participant mentions a lack of understanding regarding the physical meaning or importance of the laws governing induced currents, indicating a desire for clarification on the topic.

Areas of Agreement / Disagreement

There is no consensus on the direction of the induced current, as participants present conflicting interpretations of Lenz's law and the application of the right-hand rule.

Contextual Notes

Participants express uncertainty about the foundational principles of electromagnetic induction, particularly regarding the scope of Faraday's law and its implications for the direction of induced currents.

Who May Find This Useful

This discussion may be useful for students and enthusiasts of physics, particularly those interested in electromagnetism and the principles of induction.

llama0lover
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A magnetic field B, that is decreasing with time is directed out of the page and passes through a loop of wire in the plane of the page, as in my drawing (ignore that the dots are not evenly spaced, you can only do so much in paint) Which of the following is true of the induced current in the wire loop?

A) it is directed into the page
B)it is directed out of the page
C) It is counterclockwise in direction
D) it is clockwise in direction
E) It is zero in magnitude
 

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Okay, we got this problem now- thanks anyway, physics board!
 
Hey I'm having trouble with this problem too. What was the answer and how did you obtain it? Is it counterclockwise?
 
According to the Lenz's law, an induced current flows in a direction that opposes the change causing it.

I think in this way:
As the out-of-paper magnetic field is decreasing in magnitude, the induced current should produce a magnetic field which minimizes the effect of such a change.
Therefore, a out-of-paper magnetic field should be generated.
Thus, the induced current should flow in a counterclockwise direction by the right-hand grip rule.
 
kiwakwok said:
According to the Lenz's law, an induced current flows in a direction that opposes the change causing it.

I think in this way:
As the out-of-paper magnetic field is decreasing in magnitude, the induced current should produce a magnetic field which minimizes the effect of such a change.
Therefore, a out-of-paper magnetic field should be generated.
Thus, the induced current should flow in a counterclockwise direction by the right-hand grip rule.

Thanks! That's how I think of it too but I don't understand why it must minimize the change inside the loop and not outside the loop. If you grip it so that your fingers point out of the paper outside the loop, the current flows clockwise.
 
The reason why we just consider the change in magnetic flux enclosed by the circuit is given in Faraday's law of induction.

Frankly speaking, I do not know why the law is established in this way due to my poor knowledge in Physics. (Sorry :frown:)
I also want to know whether it has any physical meaning or importance.
 

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