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Why do only iron , nickel and cobalt can be striked to be become a magnet ?

Why do other element cannot?

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Its about the internal allignment of magnetic dipoles. The 3 mentioned allign in the same direction giving strong fields.

 

You also have paramagnetics and diamagnetics

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Manganesse is also atracted to magnets, and if you look at a PTOE they`re all side by side too :)

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Iron, nickel, amd cobalt are ferromagnetic elements with Curie points well above room temperature. Gadolinium is ferromagnetic below 16 C. Dysprosium is ferromagnetic below -188 C.

 

 

Other materials will be attracted to or repel external fields, but will not reatian the properties when the external field is removed. Diamagnetic materials have electrons whose dipoles align with the external field. Paramagnetic materials' dipoles anti-align.

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What is it about magnets exactly that makes the difference though? Is it the molecular structuring of the thing or what?

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Yeah, but why does the electron spin exsist? What makes magnetic material more suseptible to this electron spin than other materials?

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isnt that like saying why do some atoms have more protons, neutrons and electrons then others???

 

they just do!

 

(or maybe there's a better explanation than that!)

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Yeah, but why does the electron spin exsist? What makes magnetic material more suseptible to this electron spin than other materials?

 

Can't tell you why spin exists, but it does. And so some materials can have the unpaired spins line up, and the atoms form a regular structure, so that the fields add up and are permanent (below the Curie temperature, i.e. the thermal motion doesn't disrupt the alignment)

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"Can't tell you why spin exists, but it does."

 

It's surprising how even rather simple para- and diamagnetics end up in the zone of "We don't know yet and perhaps never will". And that's exactly what's great in quantum mechanics, there always seems to be something to find out. :)

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Copper and Aluminium become magnetic if a magnet is moved near them. This is something to do with Lenz Law and Eddy currents. Could magnets be made from copper and aluminium. I understand superconductor use a bit of copper and aluminium.Any comments?

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Any comments? Anyone out there? Is there a better forum for physics regarding LENZ LAW, EDDY CURRENT, PARAMAGNETIC, DIAMAGNETIC, SUPERCONDUCTIVITY, MAGLEV etc? Please direct me.

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Copper and Aluminium become magnetic if a magnet is moved near them. This is something to do with Lenz Law and Eddy currents. Could magnets be made from copper and aluminium. I understand superconductor use a bit of copper and aluminium.Any comments?

 

That's either para- or diamagnetism. For those materials, the magnetic effects only last in the presence of an external field.

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Are superconductors, SUPER magnets? Some superconductors are made of Yitrium, Barium, Copper and Oxygen. Another group consists of Bismuth, Strontium, Calcium, Copper and Oxygen. Could Copper be replaced with Aluminium as it is possible in Lenz law, eddy current etc?

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Superconductors are unusual in that they are like normal wires when it comes to magnetic fields.

 

See about the mesissner effect:

http://en.wikipedia.org/wiki/Meissner_effect

 

also apparently placing a magnetic field near a superconductor will destroy the superconductor's superconductiveness (I'm not sure if it's temporary, ie. whilst the magnet is there or more permament).

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also apparently placing a magnetic field near a superconductor will destroy the superconductor's superconductiveness (I'm not sure if it's temporary' date=' ie. whilst the magnet is there or more permament).[/quote']

 

A superconductor expels magnetic fields from its interior, see this link at hyperphysics...

Meissner effect

 

 

Are you sure you said what you mean?

 

I know if you drive the volume current density J up to high that destroys the superconductivity.

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I am sure... my physics teacher told me (and he did a PhD on superconductors, more specifically the kondo anomaly)

 

Anyway, here's a link:

http://www.physorg.com/news2937.html

 

“Usually, when you apply a magnetic field to a superconductor, the field suppresses or even destroys the superconductivity,” Bezryadin said. “The magnetic field pulls apart the two electrons forming Cooper pairs and also rotates their spins. As the superconductor becomes smaller, however, the destructive effects of the magnetic field become weaker.”

The article is about overcoming the known effect of a magnetic field destroying superconductivity, however you cannot totaly overcome it.

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Well for that you'd need to know the formula for heat loss and the critical temperature for the superconductor.

 

F = uaΔt

 

is used, but it applies for a perfectly insulated wire, so it should give a very approx answer for you.

 

heat flow = conductance x transversal surface area x change in temp (between superconductor and the air [in this case]

 

The critical temperature varies for all superconductors.

 

But because of the big temperature difference between the superconductor and the air, and because of the very low critical temperature, even for high temperature superconductors I would have at a guess not very long at all... less than a minute maybe, but thats a totaly random guess!

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I have been trying to increase the strength of a magnetic field by putting together 10 bar magnets. Let's say each bar magnet has 1 Tesla. Then 10 bar magnets put together would have 10x0.1 = 1 Tesla. So far I have not been successful. Is it possible?

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I have been trying to increase the strength of a magnetic field by putting together 10 bar magnets. Let's say each bar magnet has 1 Tesla. Then 10 bar magnets put together would have 10x0.1 = 1 Tesla. So far I have not been successful. Is it possible?

 

The field strength is the density of the flux lines. Adding magnets gives you more flux lines, but you increase the area, too. What you need to do is concentrate the flux lines: find a material that has a reasonable magnetic permeability (like soft iron and some types of steel. The core of a transformer is ideal. let's call this the mu-material), and put that at the top of the magnets. Most of the flux from all the magnets will be concentrated in the mu-material, so if the metal piece is smaller than the magnets, you will have more flux lines in a smaller area, so the field will be higher at the ends of the piece of mu-material.

 

However, at high fields you will saturate the mu-material, and it won't concentrate fields past this point.

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I don't think you meant to ask, why do electron spins exist. Becasue thats like asking why do humans exist. Well know one knows.

But the question is, even though all atoms have electrons with spin, why do some exhibit magnetic properties and others not. Well, there are two main groups, rare earth metals (lanthanum to lutetium) and the iron group.

I will now talk about energy levels within the shells of electrons of an atom. A stable atom will have filled shells and subshells, that at least makes it less reactive because for any filled shell or subshell the net angular moment and spin is 0.

In the rare earth group metals, there is an incomplete 4f subshell, meaning the electrons within will be effected by a magnetic field, their dipoles becoming aligned and they exhibit paramagnetic behaviour, but this subshell is shielded by two outter complete shells 5s and 5p, so the electrons are not affected by interactions with other atoms.

For Iron their outter most subshell 3d is incomplete, meaning that the electrons will be interacting with it's neighbours, which results in ferromagnet behaviour.

I would love to sit and write all about these two complex yet beautifully simple concepts, except I have an exam tomorrow and I keep on getting dsitracted by this website.

Richard Turton's "The Physics of Solids" is a good text covering magnetism super conductors and everything else surrounding the subjects.

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