Calculating an expression for work in a magnetic field

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Homework Help Overview

The discussion revolves around deriving a formula for calculating work done in a magnetic field, specifically involving variables such as magnetic field strength (B), area (A), resistance (R), and time (T). Participants are exploring the relationships between these variables and the application of relevant equations.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to derive the work formula using various relationships, questioning the appropriateness of certain equations like V = B * I * L, particularly in the context of solenoids. There is also discussion about the definitions and roles of variables such as L and the implications of using power equations.

Discussion Status

The discussion is ongoing, with participants providing different interpretations and calculations. Some have pointed out potential discrepancies in the derived equations, while others are seeking clarification on the use of specific formulas. There is no clear consensus yet, but various lines of reasoning are being explored.

Contextual Notes

Participants are constrained by the requirement to avoid using current (I) in their calculations, which is influencing their approaches. The original poster expresses uncertainty about the applicability of certain formulas, indicating a need for further clarification on assumptions related to solenoids.

QuickSkope
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As shown, I must derive a formula to find work.

http://i.imgur.com/0U0eLqm.jpg

I proceeded as follows.

W= F * D
= (B * I * L) * D

V = BA/T

I = V/R
= (BA/t)/R
= BA/tR

F = B * (BA/tR) * A
W = ((B^2*A^2)/tR) * A
W = (B^2 * A^3)/tR

Does that seem right? IIRC, the B*I*L formula is only for solonoids?

Thanks
 
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I don't understand this

"F = B * (BA/tR) * A
W = ((B^2*A^2)/tR) * A
W = (B^2 * A^3)/tR

However consider Power = VI and work = power X time
I think you will get a similar ansawer
 
I solved L in terms of B, A, R and T, as the question doesn't allow me to use I. Only thing I'm confused about is if I can use V = B * I * L in this situation, as I thought that was for solonoids only.
 
What is L? I recall that Force = B X current X length of wire.
Think about it this way. V = dphi/dt and this is what you have.
Power = V^2/r

Work = power X Time, yes?
 
barryj said:
What is L? I recall that Force = B X current X length of wire.
Think about it this way. V = dphi/dt and this is what you have.
Power = V^2/r

Work = power X Time, yes?

((BA/t)^2 / r) * t gives me

(BA)^2 / tR, which is a different equation then the other one I got. So is mine wrong?
 
I got (BA)^2 / tR. In your post #1 you have an extra A. There might be a math error. Do you have the correct answer?
 
Unfortuantetly, I don't have an answer. I'll check it today. Thanks :)
 

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