Calculate movement of steel in magnetic field

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Discussion Overview

The discussion revolves around calculating the force required to move a steel plate in the magnetic field of a stationary permanent magnet. Participants explore various aspects of the problem, including the properties of the steel, the configuration of the magnet, and the effects of movement in different directions relative to the magnetic field.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant asks about the force required to move a steel plate of specific dimensions in a magnetic field, noting that the movement is parallel to the magnetic field.
  • Another participant points out that the type of steel affects its magnetization properties, mentioning that low carbon steel has good magnetic properties.
  • Several participants suggest that the magnetic field strength 'B' at a distance from the magnet is crucial for calculations, and that the permeability of the steel varies significantly among different alloys.
  • One participant proposes two cases for analysis: moving the steel plate horizontally or perpendicular to the magnet, and seeks to understand the force required in both scenarios.
  • Another participant suggests that if the steel is moving much slower than the speed of light and is not charged, the motion may not significantly affect the force required to move it.
  • A participant notes that while the force on the steel due to the magnet is known, the force required to move the steel horizontally appears to be less than expected, raising questions about energy distribution during movement.
  • One participant introduces the concept of eddy currents forming in the steel when moving through a changing magnetic field, which could create resistance to motion, particularly in directions that alter the magnetic field more significantly.

Areas of Agreement / Disagreement

Participants express differing views on the effects of movement direction and the role of eddy currents, indicating that multiple competing perspectives remain without consensus on the calculations or underlying principles.

Contextual Notes

Participants highlight the importance of knowing specific properties of the steel and the magnetic field strength, as well as the complexity introduced by the size of the steel plate relative to the magnet and the distance involved. There are unresolved aspects regarding the calculations of force in different movement scenarios.

jinnkraft
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Hi

A steel plate with dimensions a * b and thickness t is moving in a magnetic field of stationary permanent magnet. the movement of steel plate is parallel to the magnet field. One pole of the magnet is perpendicular to the axis of steel movement. what force will be required to move this steel plate in the magnetic field 'B'. let he distance between the magnet and steel be 'd'

thanks
noor
 
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jinnkraft said:
Hi

A steel plate with dimensions a * b and thickness t is moving in a magnetic field of stationary permanent magnet. the movement of steel plate is parallel to the magnet field. One pole of the magnet is perpendicular to the axis of steel movement. what force will be required to move this steel plate in the magnetic field 'B'. let he distance between the magnet and steel be 'd'

thanks
noor

Welcome to the PF.

Is this for schoolwork? What is the context of the question?
 
What kind of steel? Different alloys have different magnetization properties. SS 304 is pretty much nonmagnetic.
 
Low carbon steel. it has very good magnetic property.
I want to analyse the force required to move a steel plate in magnetic field for a project.
 
Take a look at this
http://www.codecogs.com/library/physics/magnetism/magnetic-pull-force.php

You will need to know the magnetic field strength B at a distance from your magnet. If your metal plate is small compared to the distance to the magnet, then maybe you can approximate B as constant across the metal. Otherwise, it will get more complicated. Anyways, you might be able to get a gross estimate by assuming B is constant.

You need to know the permeability of the steel. This can vary a lot between alloys and tempering. http://en.wikipedia.org/wiki/Permeability_(electromagnetism) has a table of some permeability values of some materials. You see "Ferritic stainless steel (annealed)" is given as 1000-1800.

Then you can calculate the force on the metal, which will tell you the acceleration of it.
 
Khashishi said:
Take a look at this
http://www.codecogs.com/library/physics/magnetism/magnetic-pull-force.php

You will need to know the magnetic field strength B at a distance from your magnet. If your metal plate is small compared to the distance to the magnet, then maybe you can approximate B as constant across the metal. Otherwise, it will get more complicated. Anyways, you might be able to get a gross estimate by assuming B is constant.

You need to know the permeability of the steel. This can vary a lot between alloys and tempering. http://en.wikipedia.org/wiki/Permeability_(electromagnetism) has a table of some permeability values of some materials. You see "Ferritic stainless steel (annealed)" is given as 1000-1800.
Then you can calculate the force on the metal, which will tell you the acceleration of it.
hi,
thanks for your reply.
the link has to do with electromagnets and the problem is very different.
i know the magnetic field strength B. the steel is fairly bigger than the permanent magnet.
there are two cases here.

case1. steel is stationary at a distance d from the pole of magnet. i know the force with which the steel is pulled by magnet acting Normaly.
steel can be moved in two directions.
one, the steel is moved away from the magnet perpendiculary
or , steel is moved horizontally.

how to calculate the force acting on steel when it is moved
 
Hi
I'd put the problem differently.
A permanent magnet of known dimension and magnetic field strength B is fixed. A steel plate of known dimension and thickness and permeability is placed at a distance d, such that the pole of the PM faces the flat surface of steel. The force acting due to PM on steel is known.
Now, if the steel plate is moved horizontally, i.e. parallel to the pole, then i'd like to calculate the force required to move the steel plate, ignoring friction.
 
If the steel is moving much slower than the speed of light and the steel is not charged, I don't think the motion of the plate will make any difference to the force.
 
thanks for your anwer

suppose the force on steel due to magnet kept below it at a distance of 1 cm is 20 N. and if this steel is moved horizontally just to be outside its magnetic field, then the force required, to move it disregarding friction, should be atleast 20 N.
But it is observed that moving steel horizontally takes less force but towards the edge compared to moving it up along the axis.
i have seen some links that say the energy gets distributed while moving steel parallel to the magnet, but there is no formula to support this.
can you share some details on this

regards
 
  • #10
Hmm, I guess I missed an effect in my last post. If the steel is moving through a changing magnetic field, then there will be eddy currents formed in the steel which create some resistance to the motion. There will be more resistance in directions that change the magnetic field more.
 

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