Does the length of an iron bar changes when it is magnetised?

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Discussion Overview

The discussion revolves around whether the length of an iron bar changes when it is magnetized, exploring the theoretical and experimental aspects of magnetostriction in ferromagnetic materials.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants propose that the length of an iron bar does change when magnetized due to its magnetostrictive properties, though the extent of this change is dependent on various factors such as size, shape, and magnetic field strength.
  • One participant questions the mechanism behind the length increase, suggesting that the alignment of magnetic domains in the direction of the magnetic field does not inherently lead to a change in length.
  • Another participant introduces the idea that magnetizing iron involves passing it through magnetic field lines, which generates electrical currents and heat, potentially affecting the material's dimensions, albeit possibly in a negligible manner.

Areas of Agreement / Disagreement

Participants express differing views on the mechanism and significance of length change in magnetized iron, indicating that multiple competing perspectives remain without a consensus.

Contextual Notes

The discussion highlights the dependence on experimental setup and the potential for very small effects that may be difficult to measure accurately.

heman
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Does the length of an iron bar changes when it is magnetised?
 
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Theoretically yes, because iron is a magnetostrictive ferromagnetic material. The experimental measurement of this variation depends on your setup (iron bar size&shape, magnetic field strength, etc.).
 
Clive,
That' okay but how CAN the length increase.
They are just aligning in the direction of magnetic field.
 
Let's see now. To magnetize iron you have to pass it through the field lines. Doing so generates an electrical current. Current meets resistance, generates heat, hysteresis. When you heat something what happens?
Mind you, with every day magnets, the effect could be so small that it would be undetectable without some veery precise instruments.
 

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