Need help coming up with dl in cylindrical coords.

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SUMMARY

The discussion focuses on deriving the differential length element (dl) in cylindrical coordinates for calculating the force on a wire due to a magnetic field generated by another wire along the x-axis. The magnetic field is defined as \(\vect{B} = \frac{\mu_0 I}{2\pi s} \hat{\phi}\). The user seeks assistance in expressing dl in a form suitable for integration, acknowledging that both the phi hat and s hat components change along the integration path. Key equations referenced include the magnetic field formula \(B = \frac{\mu I}{2\pi r}\) and the force equations \(F = ILB\) and \(dF = IBdL\).

PREREQUISITES
  • Understanding of cylindrical coordinates and their application in physics.
  • Familiarity with magnetic fields produced by current-carrying wires.
  • Knowledge of vector calculus, particularly in the context of integration.
  • Proficiency in using the Biot-Savart Law and Lorentz force equations.
NEXT STEPS
  • Study the derivation of the Biot-Savart Law in cylindrical coordinates.
  • Learn about the application of vector calculus in electromagnetism.
  • Research the integration techniques for vector fields in cylindrical coordinates.
  • Explore examples of calculating forces on wires in magnetic fields using \(dF = IBdL\).
USEFUL FOR

Physics students, electrical engineers, and anyone involved in electromagnetism or wire interactions in magnetic fields will benefit from this discussion.

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The whole problem consists of several parts, but my issue is to come up with a dl for the piece of wire shown.

Im trying to find the force on the wire due to a magnetic field produced by another wire running along the x-axis (not shown in pic).

[tex]\vect{B} = \frac{\mu_0I}{2\pi s}\hat{\phi}[/tex]

I am trying to get my dl x B so I can integrate, but I cannot come up with a dl. The reason I'm having trouble is because I know in cylindrical, for dl, both phi hat and s hat change along integration path for dl.

Someone please help I think I've tried every method except for the one that works. :(
 
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I'm interested in this. It seems to me you need to use
B = μI/(2πr) = μI/(2πy) for the magnetic field at height y caused by the wire running along the x-axis. And for the force on the wire, wouldn't you just use
F = ILB or dF = IBdL ? You would then have to express dL as (cos θ)*dx to get an element of length perpendicular to B.
 

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