Magnetic Dipole Moment of a Coil

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Homework Help Overview

The discussion revolves around determining the magnetic dipole moment of a coil with N turns carrying a current I in a magnetic field B, which induces a torque on the coil. Participants explore the relationship between the magnetic dipole moment and torque, as well as the implications of unspecified parameters such as the area of the coil.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the expression for magnetic dipole moment as A x I, questioning the lack of specification for area A. There is also consideration of the relationship between torque and magnetic dipole moment, with some participants suggesting that the torque could be a known quantity.

Discussion Status

The discussion is active, with participants exploring different interpretations of the problem. Some guidance has been offered regarding the symbolic nature of the expressions needed, but there is no explicit consensus on how to proceed without additional information about the area.

Contextual Notes

Participants note the absence of numerical values or specific dimensions for the coil, which raises questions about how to derive the necessary expressions for magnetic dipole moment and torque.

jumbogala
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Homework Statement


You have a coil of N turns, with current I through it.

It is in a magnetic field B, which causes it to feel a torque.

Give an expression for its magnetic dipole moment.


Homework Equations





The Attempt at a Solution


Well, I know magnetic dipole moment is A x I

So for a coil of N turns it should be A x IN.

The problem is, A isn't specified in the problem, which makes me wonder if there's a better/different way to do this. Any ideas?
 
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There's an equation that relates torque to B and magnetic dipole moment. Are we to assume the torque is a known, eg. "the coil experiences a torque T"?

Without thinking through the problem completely, I'd say that equation is likely to be helpful here.
 
Yeah, that equation is t = u x B

However the next question is, "give an expression for the torque". So I think I need to find u first, then use that to find t = u x B.

Thanks though!
 
Are any numbers given in the problem at all?
 
Weird. I don't see how you can answer this, without having the area ... or some information (radius of circle, side-length of a square, etc.) that could be used to calculate area.
 
The reason I asked if any numbers were given is that the phrasing "give an expression for" could mean that it's a symbolic reasoning problem (in which case you already have the answer for the first part - you gave it in your original post - and the second part is simply a matter of plugging your answer for the first part into the relevant equation).
 
Nope, no numbers are given at all.
 
Last edited:
Alright. Well, if there are no numbers, then you're just supposed to find a symbolic expression for the quantities. You gave an expression for mu in your first post: mu = N (A x I). Plug that into the formula for torque, and you'll have your expression for torque. You can assume that A is a given, since there's no way to get mu or the torque without A.
 
Okay, thank you so much!
 

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