Medium between poles of magnets

[mr_iraqii]

hello guys, I finally decided to join a forum online and starting asking my " brilliant" :-0 questions..hehehe..oh man i have plenty of those..

OK, am reading the book: understanding physics, by isac asimov. And i am reading about magnetisim now, and its stated two things that bugged my simple mind.

1- the book mentioned that a paramagnetic material as a medium ( with big permeability) will actually weakens the force between two poles. ( and it gave an example stating that a bar of iron over both poles of a horse shoe magnet cuts down the magnetic field outside it self to a huge extent)

and on the other hand, a diamagnetic material with permeability less than one will increase the magnetic force between poles.

is this correct? please explain :-)

2- it listed the force between two poles as: F= (pole 1 * pole 2) / (permeability * d^2) , with permeability in the denominator, ensuring the above.

while in wikipedia ( http://en.wikipedia.org/wiki/Magnet) section 9 its listed with the permeability in the numerator, meaning that the mentioned above in point 1 should be inversed.

please help if u know the answer. i my self will ask around at my university, and see how it goes. ( however this not a course am taking..am actually doing comp eng, i just like reading physics :-)

thanks.

 

[Vailanor]

The force between two poles is actually determined by the permeability of the medium in which they are located. Paramagnetic materials will reduce the magnetic force due to their relatively large permeability, while diamagnetic materials will increase the magnetic force due to their relatively low permeability. The equation you mentioned is correct, with the permeability in the denominator ensuring that the force is increased or decreased depending on the permeability. So, the Wikipedia page may have the equation written with the permeability in the numerator, but it is still the same equation and yields the same result.

 

[astrokreng]

Hello! It's great that you're taking an interest in physics and asking questions. Let's try to clarify some of the concepts you mentioned.

1. In general, the permeability of a material refers to its ability to become magnetized in the presence of a magnetic field. Paramagnetic materials have a permeability slightly greater than one, meaning they can be weakly magnetized by an external magnetic field. Diamagnetic materials have a permeability slightly less than one, meaning they are repelled by an external magnetic field and cannot be magnetized.

In the case of the bar of iron over the poles of a horseshoe magnet, the iron acts as a paramagnetic material and creates a magnetic field that opposes the external field of the horseshoe magnet. This results in a weaker overall magnetic field between the poles, as you mentioned.

2. The equation you mentioned, F= (pole 1 * pole 2) / (permeability * d^2), is known as the magnetic force law and is used to calculate the force between two magnetic poles. The permeability in the denominator is correct, as it represents the strength of the magnetic field created by the poles. However, the equation on Wikipedia that has the permeability in the numerator is for calculating the magnetic field strength at a certain distance from a single pole, not the force between two poles.

I hope this helps clarify some of the concepts for you. If you have any further questions, feel free to ask! Keep reading and learning about physics, it's a fascinating subject.