What is Permanent magnet: Definition and 118 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.
Sir what would be the life of permanent magnet motor which runs by the repulsion of north pols. Is magnets energy wasted during this repulsion process or not. Because it continuously work on repulsion of two north pols.
Hello all,
I'm a mechanical engineer who recently recently became interested in linear motors and generators (random, i know). I've narrowed my interest to tubular linear permanent magnet motors (servo types) such as the ones made by these people...
this video ( ) demonstrates lenz's law, if the current produced by the magnet fall induces an opposing magnetic field , after many tries , can this field demagnetize the magnet , another thing, consider this : if the copper pipe was instead a pvc pipe, and i wrapped around it copper wires , so...
OK... so my understanding is that a DC generator under no load generates high voltages without any current, but does the same hold true for an AC alternator?
What happens with current when the RPMs of the alternator exceed what is necessary for the current requirements?
Hello all,
I am a newbie here but have a question that I was hoping someone could answer. Would a permanent magnet give off a single frequency or would it give off a spectrum of frequencies, like an incadescent light bulb can give off a spectrum of frequencies? I can measure the intensity...
If you were to levitate a superconductor using a permanent magnet due to the effects of the Messiner Effect, and you were then to lift the permanent magnet with your own hands, would you be lifting the mass of the permanent magnet, the mass of the permanent magnet + the mass of the...
Im looking to do some projects with permanent magnets.
I don't have access to a gaussmeter and I'm wondering if there are any sites that have representations, descriptions or formulas for the field strengths of ferrite or neodymium magnets.
Also i need to learn about how magnetic fields...
Homework Statement
Homework Equations
The Attempt at a Solution
What is the expression for the magnetic field of a magnet? Biot Soviet law cannot be used since there is no current. What should I do? I get stuck at the final step shown below.
New here, hello all.
My question is more about the field magnet in a running DC motor. First of all, does the current required to maintain a magnetic field change with the load on the motor? And if so, where would this "extra energy" come from in a permanent magnet DC motor?
Hi,
when a perment magnet machine is designed for a particular power but is operated at a much lower power, is it inefficient as with induction machines?
Thanks
Suppose a permanent bar-magnet is placed inside a toroid/torus and the toroid is then completed and power applied. How will the magnet move? Will it move?
Hey!
I am trying to find a permanent AlNiCo magnet with a magnetic moment of 0.06Am^2.
However, most magnet data sheets do not list the magnetic moment of their magnet. Often they list the Magnetic field in Tesla or the moment in Vs*cm. How can I convert this data into the magnetic moment...
I'd like to make a strong (~0.5 T) solenoidal field with a permanent magnet for a Faraday rotation experiment. If I take an ordinary cylindrical permanent magnet (with an axial field) and drill a hole down the center of it. What's the field deep inside at the center of the hole? Some of the flux...
If a permanent magnet rod enters a coil of wires at a certain speed will the permanent magnet slow down? I'm trying to build a generator of some sort. So i need to know is my logic sound. I'll give you scenario.
Scenario:
The permanent magnet slides into the coil at a speed of...
I was wondering what it would be like if you had a permanent magnet inside the core of a material capable of obtaining the superconducting state. And you cooled it down so that it becomes a superconductor.
Assuming it didn't explode; would it just condense the magnetic field into some...
Is it possible to estimate the magnetic field strength of a permanent magnet from the heaviest weight that the magnet can lift? The heaviest weight that can be lifted can be found by trial and error.
Any comments or suggestions appreciated.
inkpot
I've recently attempted to calculate the force of repulsion between two neodymium magnets. The problems arise fairly early when I don't know how. I know about ampere's force law and all that, but I couldn't find an equation concerning permanent magnets.
Obviously, two magnets with rectangular...
Greetings, I fabricated a PMA using vertically stacked stators and rotors. I tested the unit on a lathe and was able to gather the following data at different RPMs. The design uses the flux lines from both ends of the magnet. This configuration allows the stators and rotors to be stacked...
Hello everyone. There is a little project I could use some help with.
I would like this done in a spreadsheet, so I can mess around with different values.
The Problem:
On one hand, I have a permanent magnet and, on the other, I have a ferromagnetic object. I want to find out the force...
what happens when a permanent magnet is wound with a copper wire (inductor) and the inductor is connected to some volatge? Will the magnetic flux of the permanent magnet increase (i.e., make the permanent magnet more strong)?
This is sort of a thought experiment. I want to find out if my approach to this is correct.
How can I analytically find the magnetic field from a permanent magnet?
My approach would be to consider the magnet to be a lattice, with each lattice point being a molecule with a magnetic dipole...
A lift electromagnet has N + S pole on the same side. will it push or pull a permanent magnet which has N & S pole on opposite side? If I have a lift electromagnet and a permanent magnet, both can pull 100 lbs. What is the break away force if I put them together? Thanks
Greetings, I have been working on a permanent magnet alternator, axial flux configuration.
It has been configured with vertically staked stators and rotors. The traditional fabrication technique the stator is one large diameter with a large diameter magnet rotor above and the below the stator...
I am hoping someone here has experience with permanent magnets. I have a theory on how to size a permanent magnet for an alternator I am designing, and I want someone to confirm that my technique will yield a result that is useful enough to go through the expense of building a prototype. My...
The problem I am having is that I cannot seem to find the magneto-motive force of a permanent magnet. Most material tables give a Hc in kA/m, which I take to mean I multiply by the length of the magnet, then by the area of the magnet to get my total magneto-motive force.
So does...
So I can't seem to find out why generators aren't designed so that the coils are passing in between TWO magnets N facing in and S facing out, and then S facing in N facing out etc. The flux density between two magnets is obviously greater and the flux lines are 'straighter' (more lines of flux...
Hello
I would like to calculate the magnetic flux density given by a permanent magnet which is placed about the surface of a iron hollow sphere (assume mur = Inf). Actually, I am interested in the flux density just outside the hollow sphere.
The idea is to replace the magnet with equivalent...
I am trying to come up with a design that would track the position of a wire. The wire will have a permanent magnet attached to its tip. I will use a electromagnet to move the wire in only 1 dimension.
Here is what I was thinking... I would put a stationary aluminum plate some distance from...
Hello, I'm building a DC generator for fun (of the cardboard and lego variety). It is based on this model:
How would you calculate the power output from that, assuming we know the strength of the magnets and the frequency of rotation?
Are there any easy ways to increase...
Homework Statement
What would be the necessary magnetic field strength needed to pick up a 0.1543 lb. magnetic object 0.238 meters away? (I am trying to find a permanent magnet, not an electromagnet to accomplish this)
(the pull force of the permanent magnet I am using is 4.7 lb)Homework...
While working on a project I noticed something wonky and I don't understand how or why it is happening.
Typically if I have an inductor, the presence of a permanent magnet will reduce the inductance according to its distance - however I have started using a type of nanocrystalline core that...
Hi
If we have a Y shape iron and we put a Permanent Magnet N pole at the bottom leg of the Y in such that it will saturate it. would the top ends of the Y also be saturated. what if instead of 2 we have 20 branches where flux can go. what is the saturation will be like at one branch?
thx
Hello,
I've been extremely stuck on the following problems and was hoping someone could give me a push in the right direction:
Homework Statement
1) Given an infinite slab of permanently magnetized matter of thickness d centered on the xy-plane with uniform magnetization \textbf{M} = (0, M...
Hi.
I'm doing an experiment and I'm kinda stuck.
I know that a current produces a magnetic field. In this experiment there is a current carrying wire (copper) and a permanent magnet suspended above it. Deflection is being measured as the current is varied.
I know that both magnetic...
Homework Statement
A permanent magnet synchronous generator (as used in the wind industry) develops 5MW of electricity at 12 RPM; What amount of mechanical torque would be required to turn this generator at 12 RPM.? These generators are said to be 95% efficient
Homework Equations...
I know this may sound strange. Has anyone ever successfully created a working physical model of a magnet that exhibits the same properties ("flux" lines and attraction) without using magnetic materials or electrical influence?
Thanks
G
I would like to know if anyone here has ever been involved in permanent magnet production, and more specifically, with the sintering process. What temperature must a NdFeB magnet be heated to for sintering and also, how do you determine the length of time you sinter for? What kind of density...
I am incorporating a solar chimney in my house build in Thailand, this will have a venturi to create the suction for removing warm air from the building and I intend to use this high air speed area to generate electricity. As air speed will be dependant on the Sun and not the more fickle wind...
What is the drag force on a magnet falling through a coil? I have found several sources online describing the drag force on a magnet falling through a conductive pipe. How might this vary if a coil is used in place of a pipe? Does the coil need to be connected to a circuit to create this force?
What happens, and why? (This isn't homework, just curiosity.)
To be more precise, what would happen to the magnetic field of the magnet if we passed a current through it (assuming it is conductive). Will the current disrupt the magnetic domains? Will the magnetization disappear?
http://www.geocities.com/sc_cannon/filxb.bmp
A wire carrying a current I has a magnetic field from a permanent magnet crossing it at right angles. The force on the wire is equal to the cross product of Current Length with the Magnetic Field, B.
What is the force experienced by the...
When we magnetize a ferromagnetic material, we provide an input of energy. Is it possible to demagnetize a magnet, and convert a fraction of the energy to usable work? (Of course, this is not a useful way to generate work, and some fraction of the input energy is lost)
Hello, I'm a mechanical engineering student currently working on a project which involves a compressed air motor and a Permanent magnet DC generator.
I have this generator :
http://www.windstreampower.com/443905_PMDCG.php
Basically, we'll use the generator power output to determine the...
I'm looking for an equation to calculate Tesla (B) between two permanent magnets with distance of 10mm.
Magnets are located in front of each other; disk shape and intensity of each is 1.3T in its core, and 0.6T on surface, so I'm interested how to calculate the B between them in distance of...
G'day. I was wondering about the possibilities of making a permanent magnet hoverboard that levitates above a permanent magnet floor. They say that these new neodymium magnets can attract hundreds of kilos/pounds. Since repulsion and attraction forces are the same magnitude from what I hear, why...