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.
If I have an internal resistance of the motor and the value of flux and the generator constant, can I simulate the system's performance by a circuit with two circuits in series, one being the internal resistance, and the other being the load, and the voltage source being the armature voltage?
In order to induce a voltage in a coil, is a magnet reqired to pass through the middle of the windings? So the real question is, if I have a tube-like or sleeve-like magnet, can I pass the windings throught the inside of the magnet and still induce a current? Are both ways essentially the...
What is the most efficient way to build a permanent magnet linear generator--AC or DC, it makes no difference. I'm working on a personal project but don't know where to start. I'm assuming that a generator similar to the one inside of a ForeverFlashlight is probably the best way to go, but I'm...
[SOLVED] Rotating Magnet
I had forgotten about a web page I made several months ago. It's regarding a rotating magnet. There are some cool physics in this page so take a look
www.geocities.com/physics_world/em/rotating_magnet.htm
Back in the early 60's Edward Purcell came out with an idea...
I'm trying to build a small cyclotron and am thus searching for a magnet. I've been looking for a neodythium disc magnet that I could have cut in half to act as the two 'D' magnets in the cyclotron. The size of the magnet needs be somewhere around 12" in diameter but I can't seem to find...
[SOLVED] Refrigerator Magnet??
A magnet is suppose to have two poles the north and south, it is said that you can't ever have a magnet with only one pole. So how do refrigerator magnets work if they only have one side??
Thanks,
Daniel