horseshoe magnet forces

[the guy]

I've been pondering over this in my head for days now, and still can't decide upon what is the correct assumption.

 

If you were to hold a horseshoe magnet over a magnetic material (let's say iron) with both poles facing down, and the slowly turn it clockwise, would the poles of the iron molecules (excuse my leyman terms) eventually come to align in a circle in the direction of movement, or would they constantly reverse as the next pole passes over them?

 

Please put my mind at rest. Thank you in advance for your answers.

[Moontanman]

I've been pondering over this in my head for days now, and still can't decide upon what is the correct assumption.

 

If you were to hold a horseshoe magnet over a magnetic material (let's say iron) with both poles facing down, and the slowly turn it clockwise, would the poles of the iron molecules (excuse my leyman terms) eventually come to align in a circle in the direction of movement, or would they constantly reverse as the next pole passes over them?

 

Please put my mind at rest. Thank you in advance for your answers.

 

 

I think you might see either one depending on the strength of the magnet and the weight of the magnetic material.

[Enthalpy]

Some ferromagnetic materials are called "soft" as they forget their magnetic history. Desired for transformers cores for instance, where the induction reverses 100 or 120 times in a second.

 

Other ferromagnetic materials are called "hard" and keep a polarization when the cause is removed. Magnets are an extreme case. Ferromagnetic materials - mostly steel - not designed for magnetic uses tend to be rather soft, but not soft enough for magnetic uses.

 

In the described situation, iron would retain a polarization much weaker than the one they get when the magnet is near. Also, this action doesn't cumulate significantly. Even less so because the magnet shows alternating poles to the iron, which, if the field is made to decrease slowly, is a means to erase the magnetizatio of iron. Sound tapes were erased this way.

 

A practical example is an induction cooker, where the pan must be ferromagnetic and not too soft, so losses in the pan heat it when the field reverses. As you remove the pan from the cooker, it retains nearly no magnetization.