Calculating magnetic field strength through objects.

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Discussion Overview

The discussion revolves around calculating the strength of a magnetic field as it passes through a concrete wall. Participants explore the effects of the wall's properties on the magnetic field, considering factors such as the type of magnet and the geometry of the field.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about calculating the magnetic field strength on the other side of a concrete wall given a specific initial magnetic field strength.
  • Another participant suggests that the influence of the concrete wall on the magnetic field may be minimal if it does not contain steel, but notes that the initial field strength alone does not provide a complete picture.
  • A participant proposes modeling the magnetic field as generated by a long solenoid and asks if there is a specific equation for determining the loss of magnetic stray field strength when passing through a material.
  • Concerns are raised about the potential decrease in field strength over distance, even without the wall, and the need for the initial field strength in the absence of the wall.
  • Further elaboration on solenoid characteristics indicates that the length of the solenoid and nearby magnetic materials can significantly affect the field strength, with a suggestion that simulations may be necessary for accurate predictions.
  • A participant with experience in electromagnetic fields and concrete emphasizes the importance of measuring the specific characteristics of the concrete used, as variations in composition can impact the results.

Areas of Agreement / Disagreement

Participants express differing views on the influence of the concrete wall on the magnetic field, with some suggesting minimal impact while others highlight the importance of the wall's material properties. The discussion remains unresolved regarding the specific calculations and effects involved.

Contextual Notes

Participants note the dependence on various factors such as the type of concrete, the presence of ferrous materials, and the geometry of the magnetic field, which complicate the calculations and predictions.

LordBerkley
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If I have a magnetic field of say 5 Tesla which is 3m from a concrete wall 0.25m thick how would I go about calculating the strength of the magnetic field on the other side of the wall?

Any help/guidance much appreciated!
 
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That depends on the size of your magnet and its field geometry. The concrete wall won't influence the field significantly if there is no steel inside, but the maximal field strength (5T) is not enough to describe a magnetic field.
 
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Take the field to be generated by a long solenoid, with a coil diameter of 1m. Is there a specific equation to give the loss of magnetic stray field strength when passing through a material?
 
The problem is that even without the wall the field may decrease dramatically over a distance of 25 cm. Do you know the field in the absence of the wall?
 
LordBerkley said:
Take the field to be generated by a long solenoid, with a coil diameter of 1m.
Then it will still depend on the length of the solenoid (as long as it is not >>10m).
And it will depend on everything (ferro-)magnetic nearby.

For solenoids, there are formulas for the field strength.
Is there a specific equation to give the loss of magnetic stray field strength when passing through a material?
Not in general. You will need a simulation, but the effect will be small as concrete is not ferromagnetic.
 
Dear,
I have been working for long in the electromagnetic fields interaction with concrete. I would say that depending on the purpose of your test, you should carefully measure the characteristics of the concrete that you are using, as there are some concretes that use ferrous sands or gravels, which can affect your measurements.
Yours,
 

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