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.

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  1. bhall

    I Speed of magnetic flux propagation?

    I have a case where I'm combining a N42 permanent magnet with two coils (20 AWG, 56 turns each, wired in parallel) to create flux transfer. Although model tools such as FEMM or SimScale model a static state of flux interaction, it seems clear based on experimentation that the flux interaction...
  2. J

    I Is this solenoid / permanent magnet configuration possible?

  3. P

    A Identifying Magnet Grade for FEMM Simulation: Neodymium Cylinder Magnets

    Hello. I need to indetify a magnet grade from an academic paper, they dont mention what grade is . I am trying to simulate de contact force bewten two magnets on FEMM and to validate the results I am using one ecuation of that paper, but they dont specify what grade the Neodymium magnet is...
  4. M

    B Basic Straight Line Permanent Magnet Accelerator

    I stumbled upon this video on YouTube: Here is a screenshot with some colored lines added of the part that generated a few questions in my head that I hope some of you smart folk can answer for me. In the video, the spherical magnet (at the end near the two big magnets) appears to increase...
  5. M

    Calculating the force that a permanent magnet exerts on a particle

    Dear readers, I have a question regarding permanent magnets and the force they generate on particles, which is far from my comfort zone. I have the option on using two types of permanent magnets and with two different setups. Imagine that we want to attract small particles using the magnets...
  6. M

    Engineering Torque calculation of a motor with permanent magnets

    $$Vstator_{peak} = 120√2 *√2 = 240 V$$ $$Istator_{peak} = i_{q} (current on q axis)= 20*√2 = 28.2842 A $$ $$ω{15} = Ω_{15} * p = 2π * 15 = 94.2477 rad/s$$ $$ω{15} = Ω_{15} * ψ_{pm}$$ Hence $$ψ_{pm} = e0/ω15 = 168.3V/94.2477 rad/s => ψ_{pm} = 1.79 Wb$$ $$M = 3/2 * p * ψ_{pm} * iq $$ Hence $$ M...
  7. Y_G

    Optimetrics simulation of a coil and moving permanent magnet in Ansys Maxwell

    I'm trying to simulate a Magnetostatic problem. In my model there are two coils and a reciprocating permanent magnet. I defined a parameter, Xpm (movement of permanent magnet) in x direction to imply the reciprocating movement of permanent magnet like a piston. Xpm = f(t). I defined "t" as sweep...
  8. George-M

    Best permanent magnet arrangement?

    If I have a block of N52 and I want to make it's magnetic field as strong as possible, would a Halbach array give me this maximum or is there a different pole arrangement/array that would provide this? I'm thinking for the use in a motor, so the field doesn't have to be large. A close field...
  9. Fdtroya

    Which factors determine the power output of a permanent magnet alternator

    To be more precise the generator has to be able to produce around 1.5 Watts from a person spinning its axis, which is why I was thinking of putting a gearbox in my design but I need to know how much Torque would it take to spin the axis and at what rpm would the generator be effective.
  10. N

    Formula to calculate the pull force between a magnet and a steel plate

    i have a neobydium magnet of grade n40 , the diameter of magnet is 15mm and thickness is 10 mm , now i want to calculate the pull force between this magnet and a steel plate when there is no gap between them ; & in second case i want to calculate the pull force when i put a 0.15mm copper plate...
  11. S

    Ansys Maxwell -- How do I add a permanent magnet into my simulation?

    hi all I am going to do a project in ansys maxwel, actually i need to add a magnet and i know i have to do it with add material. my magnet is NdFeB . i give the material from net, actually i can not valid them because they are different in value. I need to calculate Mu(permeability ) and I nedd...
  12. M

    Origins of magnetic fields from permanent static magnets versus current

    The videos from Veritasium explaining permanent static magnets and electromagnets were quite good I thought… But they have me a little confused with regard to the origins of magnetic fields generated by an electric current as opposed to a permanent static magnet from say iron. 1. An...
  13. S

    Magnetic force between an unknown and known permanent magnet

    Dear helpers, I working on an projekt for the University and for that I have to calculate forces between different magnets. The question that I have is: "Is there a way to calculate the force between two magnets if one is completely known and the other unkown. But you know the B-field of the...
  14. Dante Meira

    Repulsion between permanent magnet and air core coil

    I formulated a statement about the repulsion between a permanent magnet and an air core coil (electromagnets without a ferromagnetic or ferrimagnetic core), and I believe this statement is true, but I would like to seek the opinion of others about it: "In a system where an electromagnet made...
  15. Dante Meira

    Magnetic repulsion between a permanent magnet and an air coil

    I would like to receive some input about this "equation" formulated by me, a=f(i), regarding a system with a permanent magnet and an air core coil acting as an electromagnet, as described in the image: I understand that the acceleration provided to the toy car will be a function of the...
  16. T

    Eddy Current Speedometer Experiment

    Trying to create an experiment that utilizes a motor driven shaft to measure the angular velocity of another shaft via eddy currents. We made a mock experiment that uses 8mm shafts, pillow bearings, and ceramic magnets from home depot, but don't see a torque on a non-ferrous metal attached to a...
  17. Y

    Rolls Royce permanent magnet thruster questions

    Hello, I am considering an attempt at building or modifying a device inspired by the following, as well as others: I don't know how I would make a driver for such a thing. Would it need to be software driven for example? Any input to point me in the right direction would be very helpful to me...
  18. F

    Induced voltage in a coil in a three phase permanent magnet axial flux generator

    I am currently designing a three phase permanent magnet axial flux generator, but have a question regarding the voltage induced in the copper coils. Faraday's law defines this voltage as the number of turns in the coil, times the change in flux (external magnetic field times area of coil) over...
  19. B

    Simulation Software for a Permanent Magnet Alternator Design

    I am looking to try some design ideas using PMs for alternator design. I am a retired EE so I do not have corporate capital for simulation software. Does anyone know of low to medium cost simulation software that might be workable for basic flux/emf/etc calculations and modeling? Or other...
  20. C

    How to test toroidal permanent magnet with inside field

    As the permanent magnet is magnetized by donut shape coil, thus field B = 0 outside. How can I know if seller screwed me or not?
  21. P

    How do I design a Permanent Magnet Synchronous Generator?

    Hi, I'm trying to do a very simple analysis on Simulink where I am applying a speed to a Permanent Magnet Synchronous Generator with a purely resistive load. I'm not familiar with PMSGs so the results I'm getting don't really make any sense to me. Could anyone go through some simple design...
  22. G

    Can stationary permanent magnet do work?

    We have a permanent saturated magnet. And a coil wound around it. The current produces magnetic field in same direction as the magnet. Now we know that the energy of magnetic field is proportional to the square of the magnetic induction. E1=kB12 E2=kB22 Etotal=kB12+kB22+2kB1B2 We have an extra...
  23. P

    Forces between a Solenoid and an External Permanent Magnet

    What happens if I have a permanent magnet outside an ideal solenoid? Does the permanent magnet rotate until the system reaches an energy minimum in its magnetic fields? Or does the permanent magnet fail to rotate because the magnetic field of the solenoid does not reach the magnet? Wouldn't...
  24. A

    Problem with permanent magnet synchronous machine simulink

    Hi I would ask someone that is pratical with Simulink in particular of Simscape about a problem which involve my simulation in Matlab-Simulink of a permanent magnet synchronous machine that is connected, by a rectifier, to a DC current source. all the blocks of the simuation are included into...
  25. Ali Durrani

    Permanent magnet motor drive train

    Hello there, can anyone tell me what is a permanent magnet motor drive train and what is the working principle of permanent magnet motor drive train ? i have searched google but i couldn't find anything useful
  26. jfizzix

    Can you cancel part of a permanent magnet field by spinning?

    It's a random thought I had. Let's say you have a single perfect permanent magnet. There is just one magnetic domain, and the magnet is cut so that its magnetic moment is along a single crystal axis. For example, we can imagine a cube shaped magnet, with the magnetic moment pointing straight...
  27. T

    Approximating Field of Permanent Magnet with Micro-Currents?

    According to theory, the magnetic field of a permanent magnet is due to the combined effects of billions of microscopic magnetic moments. I'm trying to use the Biot -Savart Law for billions of microscopic currents to approximate a the field of a permanent magnet. How should these currents (or...
  28. A

    Best design for a 300 watt permanent magnet brushed DC motor

    I have noticed there are a few designs for permanent magnet brushed DC motor, but I can't seem to find the benefits and downsides of either one. The first one (first attachment) uses three electromagnets placed on a triangular rotor. There are two arc permanent magnets on the outside. In this...
  29. Chris Fuccillo

    Force on a permanent magnet from an electromagnet

    Hi again and thank you again for the help If I have two magnetic fields, one permanent ring magnet B2 free floating on a fixed electromagnetic coil B1 and the field are perpendicular 90 deg to each other will the free floating permanent ring magnet feel a strong magnetic torque and rotate...
  30. DeathCheese

    Calculate force on Permanent Magnet near a Paramagnetic surface

    Hello all, new here but plan to stick around for a while. I am currently trying to make a sensor that can detect if a material below it is paramagnetic. I believe paramagnetic is the proper term, but it needs to detect if the force exerted by permanent magnet is above a certain threshold. The...
  31. xareu

    Work done by permanent magnets

    I recall that the energy stored in a magnetic field is half the volume integral of the dot product of magnetic field and flux density vectors (H and B). When you place a piece of iron near a magnet, it does a work by attracting it. If H is 0 (I think there is only the magnetic moment vector M...
  32. N

    Will ferromagnetic dust retain magnetism in molten aluminum?

    Curie temperature for magnetite is 858 C, for iron 1043 C. Duralumin melting point is about 630 C. Does this mean that if I take a small silicone mold, place a magnet underneath it, add ferromagnetic powder to the mold and then pour molten aluminum in, I will get the aluminum detail with...
  33. R

    Big rotor vs multiple small rotors in a Permanent Magnet Generator

    Hello guys, I am trying to build a permanent magnet generator, I have 48 magnets and 18 coils, and I am hesitating betwen 2 configurations. Configuration A: 2 huge steel plates with 24 magnets on each and an 18 coil stator between them or Configuration B: 4 smaller plates stacked to sandwich 3...
  34. P

    Calculating Work for Permanent Magnet Fields

    Hi, I would like to evaluate the required work to create a 1 T field with a permanent magnet. I saw a few formulas on the internet, but I don't know how to use them correctly. The main one are B={{\mu }_{0}}\left( H+M \right) {{W}_{mag}}=\frac{{{B}^{2}}}{2{{\mu }_{0}}}Vol Let's say I know all...
  35. MironeDagains

    Very basic electromagnet vs permanent magnet question

    When you switch on an electromagnet (who's north pole is pointing to the left), is it the same thing as if you had pushed a permanent magnet to the left? Or to the right? I believe it's to the left. But apparently my textbook thinks it's to the right. Who's correct? Why I'm asking:I've attached...
  36. A

    Control strength of permanent magnet

    How to control magnetic field produced by a permanent magnet which is being induced on to a coil ?
  37. Baluncore

    What is the effect of permanent magnet strength in generator

  38. James O'Neill

    Magnetic Fields & Gears: How Magnets Affect Gear Teeth

    If you put magnets in a gear (like in an Internal Permanent Magnet motor), what effect would the gear's teeth have on the magnetic fields?
  39. J

    Commercial transformers for variable frequency & voltage

    I am looking to step up the voltage of a 3 phase PM generator which has variable AC output of 200 - 400 Vl-l, and 15 - 30Hz. I am looking for a step up ratio between 1:1.5 and 1:2, and need this transformer to be a commercial device. What i have been finding is that most commercial...
  40. S

    [ansys] simulation of permanent magnet in 3D

    Homework Statement The problem is to model a permanent magnet with a torus core .I just wanted to know how to attach attribute of magnet to a volume in ansys 15.0. I solved the problem in 2D but in 3D the results are not satisfactory and I'm not able to point out the mistake by me. the...
  41. S

    [ansys] simulation of permanent magnet in 3D

    I''m facing problem in modelling and analyzing a permanent magnet in 3D. kindly help me out.
  42. L

    Lightest Strongest magnet I can buy

    Hi All, I am wanting to buy the lightest, strongest magnet I can. Can someone please direct me or give me guidance on this issue? I am requiring a magnetic field of >5000 surface gauss. Any links or direction would be terrific, Thanks in advance, Dale.
  43. R

    Finding forces/torques on a permanent magnet from a coil

    I want to know what methods there are for calculating forces by a current-carrying coil on a permanent magnet (the application I have in mind is electrical motors). I.e. given a geometry (like a CAD model of the magnet), the magnet type (e.g neodymium), and wire coil geometry, how are the forces...
  44. ryanuser

    Fluid that is a permanent magnet at room temperature?

    Hi Is there any fluid that is a permanent magnet at room temperature? (Ferrofluids do not retain their magnetic effect hence temporary). Thanks
  45. EddieP

    Repelling a very weak permanent magnet with an electromagnet

    I have a question about magnetic repulsion. Suppose I have a permanent magnet (axially magnetized) placed on top of the iron core of an electromagnet. I want to switch on the elctromagnet to repel the permanent magnet. (Please assume the permanent magnet is contained in some kind of tube that...
  46. I

    Magnetic field of permanent magnet on ansys and comsol

    I have a problem in modelling a magnetic field of permanent magnet on ansys and comsol .I'm very thankful to you if you guide me or provide me a tutorial .thank...
  47. S

    Magnetic anode for copper cathode battery

    Hello everyone from the Physics Forums, I'm doing a school project and I'm looking for a potential anode alloy that is ferromagnetic which I could use with a copper cathode. I'm making a battery and I have to use copper as my cathode mainly because I have made the cathode cells structured...
  48. A

    Semicircular Permanent Magnet Rail Gun - continuous motion?

    Doubtless you are all familiar with a rail gun made by using permanent magnets. An example is given here: http://sci-toys.com/scitoys/scitoys/magnets/gauss.html Assuming the railgun could me made curved, won't it be possible to build a curved track to transport the projectile - assume...
  49. P

    Magnet configuration for spinning permanent magnet induction heating

    Watch this video: Permanent magnets moving relative to a stationary copper tube generate Eddy currents which result in Joule heating of the copper. Simple enough. Let's change the problem to a rotor with 4 (circumferential) permanent magnets rotating inside a stationary (aluminum or...
  50. M

    Does a permanent magnet looses its magnetism?

    The question is slightly deceiving however still simple for those academics therefore, here I present my question: If I take a para-magnetic material and put it very close to a homogeneous magnetic field, the para magnetic material will start to accelerate towards the magnetic body thus it...
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