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Anne Marie Helmenstine, Ph.D.

How Magnets Work

By April 8, 2012

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A magnet is any material capable of producing a magnetic field. Since any moving electric charge generates a magnetic field, electrons are tiny magnets. However, the electrons in most materials are randomly oriented, so there is little or no net magnetic field. To put it simply, the electrons in a magnet tend to be oriented the same way. This happens naturally in many ions, atoms, and materials when they are cooled, but isn't as common at room temperature. Some elements (e.g., iron, cobalt, and nickel) are ferromagnetic (can be induced to become magnetized in a magnetic field) at room temperature. For these elements, the electrical potential is lowest when the magnetic moments of the valence electrons are aligned. Many other elements are diamagnetic. The unpaired atoms in diamagnetic materials generate a field that weakly repels a magnet. Some materials don't react with magnets at all.

The atomic magnetic dipole is the source of magnetism. On the atomic level, magnetic dipoles mainly are the result of two types of movement of the electrons. There is the orbital motion of the electron around the nucleus, which produces an orbital dipole magnetic moment. The other component of the electron magnetic moment is due to the spin dipole magnetic moment. However, the movement of electrons around the nucleus isn't really an orbit, nor is the spin dipole magnetic moment associated with actual 'spinning' of the electrons. Unpaired electrons tend to contribute to a material's ability to become magnetic, since the electron magnetic moment can't be totally canceled out when there are 'odd' electrons.

The protons and neutrons in the nucleus also have orbital and spin angular momentum, and magnetic moments. The nuclear magnetic moment is much weaker than the electronic magnetic moment, because although the angular momentum of the different particles may be comparable, the magnetic moment is inversely proportional to mass (mass of an electron is much less than that of a proton or neutron). The weaker nuclear magnetic moment is responsible for nuclear magnetic resonance (NMR), which is used for magnetic resonance imaging (MRI).

Make a Liquid Magnet | Bend Water with Static
Image: Practical Physics, Macmillan and Company (1914)

Comments

October 8, 2007 at 12:12 pm
(1) Steven Cohen says:

Dear Dr. Helmenstine,
I have been meaning to thank you for a long time. Your clearly written articles are invaluable and I have incorporated them in my biology and introductory chemistry classes for two years.
So it was with eager anticipation that I read your article on “How Magnets Work” hoping to finally get some insight into the mystery of magnetism. I often confess to my kids that I don’t “believe” in magnetism because I can’t understand it. Perhaps this is one of the wonders of science that I will never understand, your valiant efforts not withstanding.
Thanks for tackling the problem, but I am still mystified by magnetism.

Again, thanks for your valuable articles. I read them with admiration and gratitude.

Sincerely,
Steven Cohen, PhD

July 8, 2008 at 9:13 pm
(2) dana says:

Everyone is mystified by magnets. There is an article about the lack of understanding of magnetics in Discover either June or July of 08.

March 2, 2010 at 2:45 pm
(3) mitchel kennedy says:

Im a kid in highschool still, but i can’t help myself but to try wonder. When u say, “Since any moving electric charge generates a magnetic field, electrons are tiny magnets.” I asumed that electrons get their charge from friction. But friction against what? I dont no of anything smaller then an electron and if the only friction for an electron is for it to rub against anouther, then how does and electron it self in movement have a magnetic field?

December 24, 2010 at 10:10 am
(4) Raj says:

The magnetism still is largely unexplained at its most fundemental level. For example, how is the magnetic field carried from a magnet to another object that’s attracted by that magnet ? Magnets attract each other perfectly in vaccum. So the so called magnetic ‘field’ should have a physical particle that’s ‘transmitted’ from one object (magnet) to another (object that’s attracted). Every text book says there is magnetic field but don’t see any convincing explanaion on how this field is propagated.

November 2, 2011 at 2:55 pm
(5) Pico says:

I do not believe this article one bit. There is no explanation for magnets other than magic. Science is all fake.

January 24, 2012 at 5:21 pm
(6) Victoria says:

I enjoyed this article. It was well-written and quite clear. However, I am confused about one point:

“…nor is the spin dipole magnetic moment associated with actual ‘spinning’ of the electrons. ”

From at least one source (http://en.wikipedia.org/wiki/Magnetic_moment), the spin dipole magnetic moment is calculated based on angular momentum. But according to http://en.wikipedia.org/wiki/Spin_(physics), “The spin of a charged particle is associated with a magnetic dipole moment with a g-factor differing from 1. This could only occur classically if the internal charge of the particle were distributed differently from its mass.”

So, are you saying that the electrons, in fact, do not spin? Or do you mean that there are problems when we try to understand an electrons magnetic moment due to the rotation movement alone? Or …

Thank you. :)

December 7, 2012 at 11:42 am
(7) sunnykpati says:

Though I’m fourteen your article has been greatly helpful and thank you:-)

March 16, 2013 at 4:16 am
(8) Prakash Patil says:

@Steven Cohen: Magnetism is like the old physics that was thought to have been solved totally but was reopened by Albert Einstein. We really need a new Einstein to explain it.

@mitchel kennedy: Nice thinking bro, even I feel that there is something smaller than elctron. And if nothing can be created nor destroyed, if everything gets tranformed from one form to another then to what electron gets transformed to ?

@Victoria: Even our body has got electrons, if electrons always rotate around its atoms’ nucleus and if they can be polarized then can our body too be polarized ? Can we become a magnet in certain magnetic field ?

June 19, 2013 at 8:18 am
(9) meg says:

how does it work

June 21, 2013 at 4:48 pm
(10) Hugh says:

My wonder is this: I thought that the actual position of an electron cannot be known – only probabilistically estimated, thus the description of the “electron cloud”. Given that the atom itself is charged one way or another, leading to what I believe may be valence charge, then the actual magentic dipole created with the atomic structure is between the electron cloud and the nucleus itself, leading to residual magnetic effect. The problem with that idea is that the electron cloud isn’t oriented. So how are the atoms able to align to create the overall magentic effect as described within this article? The assertions of the article have merit, though because magnetic articles lose their magnetism when heated. So I believe the actual cause of magnetism goes deeper into the atom than this explanation.

October 29, 2013 at 9:47 am
(11) Garrett Brooks says:

Best magnetic report I have seen yet.

March 23, 2014 at 5:36 am
(12) William Boeder says:

Anne Marie, I must thank you for your generosity to enter your fields of knowledge, I have to say that I am super impressed with all of the female species that enter into such complex matters.
There should be more recognition accorded to people of your intellectual capacity.

Thanks.

William Boeder.
Australia.

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