Measuring Magnetic Field Strength of a Cylindrical Magnet

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Discussion Overview

The discussion centers on quantifying the strength of the magnetic field produced by a permanent cylindrical magnet, specifically focusing on the transverse direction rather than the longitudinal axis. Participants explore theoretical approaches and numerical methods for calculating the field strength.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to understand the magnetic field strength in the transverse direction of a cylindrical magnet, noting existing equations primarily address the longitudinal axis.
  • Another participant mentions that the finite nature of the cylindrical magnet introduces edging effects, complicating the calculations and suggesting a numerical approach as more suitable.
  • A participant questions whether the magnetic field strength at a considerable distance from the magnet would follow a proportionality of 1/R^2, 1/R, or 1/R^3, expressing difficulty with the integral calculations provided in the reference.
  • A later reply indicates that at a long distance, the leading-order multipole approximation can be used, identifying the dipole as the relevant model and stating that the magnitude of the field strength decreases as 1/r^3.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate models and methods for calculating the magnetic field strength, indicating that multiple competing approaches remain without consensus on the best method.

Contextual Notes

The discussion highlights limitations in the complexity of the calculations and the assumptions regarding distance and magnet dimensions, which may affect the applicability of different models.

PhDnotForMe
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Hello,
Today I am wondering if anyone can help me quantify the strength of the magnetic field created by a permanent cylindrical magnet. I have been able to find equations online for the strength of the field within the z axis, (ie. the longitudinal length) but I would like to know the strength of the magnetic field in the transverse direction, or the strength of the magnetic field in the outward direction rather than on top or below.
 
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Likes   Reactions: PhDnotForMe, vanhees71 and anorlunda
Pythagorean said:
A cylindrical magnet is finite and, therefore, has edging effects. It's not a straightforward calculation, but Wolfram Alpha briefly touches the calculation superficially (and notes that the guts are complicated) favoring a numerical approach.

http://demonstrations.wolfram.com/MagneticFieldOfACylindricalBarMagnet/
Thanks for that great reference. The equations listed are pretty intense. If you considered a point in the transverse direction REAALLY far away, and the length and diameter of the magnet are small in comparison, would the strength of magnetic field be roughly proportionate to 1/R^2? 1/R? 1/R^3? The integral listed in the reference is way to difficult for me to estimate the macro-behavior.
 
At a very long distance (compared to the extension of the magnet) you can use the leading-order multipole, which in this case is a dipole. The magnitude goes like ##1/r^3##.
 

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