Total magnetic moment of simple system.

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Discussion Overview

The discussion revolves around calculating the total magnetic moment of a rectangular conductor carrying a current in a magnetic field, specifically when the angle between the normal vector of the surface and the magnetic induction vector is 60 degrees. The conversation explores the implications of this angle and the relationship between magnetic moment and torque in the context of electromagnetism.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant states that the formula for magnetic moment is \( m = SI \), where \( S \) is the area and \( I \) is the current, and notes that the magnetic moment direction aligns with the normal vector of the surface.
  • Another participant argues that the problem is incomplete or misworded, suggesting that the question should focus on the torque \( \tau = m \times B \) instead of just the magnetic moment.
  • Some participants express uncertainty about whether the original question can be answered using the magnetic induction vector \( B \), indicating a lack of clarity on how to relate \( B \) to the magnetic moment \( m \).
  • There is a discussion about terminology, where one participant emphasizes that "torque" is the correct term in electromagnetism for the effect of a magnetic moment in a magnetic field, as opposed to using "moment" which could lead to confusion.

Areas of Agreement / Disagreement

Participants generally agree that the question may be misworded and that torque is a relevant consideration. However, there is no consensus on how to proceed with the calculation of the magnetic moment or its relationship to the magnetic induction vector.

Contextual Notes

Participants note that the problem lacks clarity regarding the use of the magnetic induction vector \( B \) in determining the magnetic moment \( m \), and there is ambiguity in the terminology used to describe the concepts involved.

cdummie
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Homework Statement


If there's a current I flowing through the rectangular conductor and it's located in the magnetic field in such way that normal vector of the surface that this rectangle forms closes the angle of 60 degrees with magnetic induction vector find total magnetic moment of this system

Homework Equations


m[/B]=SI

The Attempt at a Solution


Formula for magnetic moment is m=SI where m is magnetic moment, S is the area of surface and I is the current. It is obvious that magnetic moment has the same direction as vector that is normal to the surface. This seems done to me now, but obviously it isn't since i am supposed to use the fact that i know direction of magnetic induction vector, but i just don't know how i am supposed to do that.
 
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The problem seems rather incomplete and/or misworded. With a magnetic moment in a magnetic field, there is a torque ## \tau =m \times B ##. (Formula is a vector cross product.). The vector cross product is the reason the angle of 60 degrees would be important. It seems a more proper question to ask would be "what is the torque on the magnetic moment?" ...editing...perhaps in very loose wording, a torque can also be called a "moment" because they call it a "moment arm" etc., but the "torque" should really be called the "torque".
 
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Charles Link said:
The problem seems rather incomplete and/or misworded. With a magnetic moment in a magnetic field, there is a torque ## \tau =m \times B ##. (Formula is a vector cross product.). The vector cross product is the reason the angle of 60 degrees would be important. It seems a more proper question to ask would be "what is the torque on the magnetic moment?" ...editing...perhaps in very loose wording, a torque can also be called a "moment" because they call it a "moment arm" etc., but the "torque" should really be called the "torque".

That's exactly what i thought, it might be that they meant a torque on the magnetic moment, but i wasn't completely sure. Anyway, i needed approval that i can't determine m by using the fact that i know B, i mean, that there's no formula that is used to determine m by knowing B.
 
cdummie said:
That's exactly what i thought, it might be that they meant a torque on the magnetic moment, but i wasn't completely sure. Anyway, i needed approval that i can't determine m by using the fact that i know B, i mean, that there's no formula that is used to determine m by knowing B.
I think in a mechanics class I have heard the rxF's on a lever arm referred to as moments, but in E&M the word "moment" should be reserved for the "magnetic moment". The word torque is the proper term in E&M for the rxF generated when a magnetic moment ## m=I*A ## is found in a magnetic field ## B ##. This torque ## \tau=m \times B ##. The torque that occurs on a current loop of area A and current I in a magnetic field B is a simple follow-on from the force F that occurs on a wire of length L and current I in a magnetic field B: ## F=IL \times B ##.
 
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