What is permanent magnets: Definition and 61 Discussions
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.
A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.
Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.
An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it but stops being a magnet when the current stops. Often, the coil is wrapped around a core of "soft" ferromagnetic material such as mild steel, which greatly enhances the magnetic field produced by the coil.
Does a permanent magnet ever loose it's energy or decrease over time? I read somewhere that a "fixed" magnet's energy will dissipate in time as it does work. I don't know what they mean by fixed.
Also, will a permanent magnet work without the Earth's energy (eg. in space).
Hello!
I have a deeply magnetizing question. I have an attractive magnetic assembly and I am interested in finding some forces, acting on its parts.
Set-up details ( if to be specific ):
I have two cylinder-shaped neo magnets with identical dimensions and properties, such as residual...
Hi all,
i saw many times while browsing that persons like howard johnson, tom beardson, paul monus, etc., are informing themselves that they have invented motors that run only based on the stored energy of the permanent magnets... are they really having that machines..? if yes, i...
I was surprise to find that even HowStuffWorks.com didn't have an article for 'permanaent magnets'. I was wondering, do permanent magnets always have magnetic fields aroung them? What makes them permanent?
Hi all,
In one of the books I'm reading, it says that shields are only used in the presence of alternating fields. However, in some websites, I see people using magnetic shields for permanent magnets which has a magnetostatic field. I ran some simulations, and the filed of a permanent magnet...
Hi all,
I have this simple question that I never really understood. A permanent magnet generates a magnetic field around itself. Is there an electromagnetic wave propagation associated with this permanent magnet? If so, what is the frequency of the wave?
Thanks,
Mike
Is it possible to produce electricity by using permanent magnets with no moving parts?
I believe that is possible. Because AC current produced by moving armature or copper wire or some other metal in magnetic field. Then without moving wire it should produce DC or some kind of electron flow...
I have a few questions about permanent magnets:
What are the most powerful permanent magnets made of? How strong do they get?
What are the ways to make an already powerful magnet even stronger?
I understand that placing iron behind it will amplify it. Why?
I also read somewhere...
I am posting this here because I have not been able to find the answer anywhere else. I know some of you might find this quite dumb of me, since I have seen some quite learned scholars in this forum, and my question is pretty basic. I am aware I might not be in the right forum.
My...
DO NOT TRY THIS EXCEPT ON A JUNK
TV OR MONITOR
If you hold a strong permanent
magnet up to a T.V. screen while
it is on, the magnetic field
does some really intriguing
warping of the image. When you
take the magnet away the image
goes back to normal except that
the color is now patchy and in-...
My physics teacher gave the class a brief explanation of a permanent magnet. If I understood him correctly he basically said the special condition with a permanent magnet is that all the electrons are circling uniformly (in same direction). The poles of the magnet are based on the direction the...