What is Magnets: Definition and 562 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. C

    B Do Magnets Emit Harmful Radiation?

    Hi. No real physics background here so bare with me. Do magnets (ceramic ferrite and neodymium magnets) emit ionizing radiation? Many products use these types, including children’s magnet tiles and electronics. Can they pose a radiation and cancer risk as a result?
  2. G

    I How Does a Magnetic Repulsion Machine Work?

    Someone on a machining forum is proposing a curiosity machine. Imagine two magnets, constrained to move along one axis, set N to N. They will move apart. If you insert a piece of steel in the gap, the magnets will move towards it. The input of the machine will be a rotating toothed...
  3. N

    Why Does Changing Wire Gauge Affect Voltage and Current in a Generator?

    I am building a small generator. 12 - 5/8″ magnets rotating around 9 - 3/4″ diameter, 28-gauge copper enameled wire. Not under load, I am getting 50 volts at 1 amp. But when I increase the wire size to 24-gauge, I am getting 15 volts at .25 amps. I thought amps go up when volts go down.
  4. J

    I Magnets, Outer space, and Rings

    Awhile back there was a discussion about the following scenario: an astronaut sets free into space outside his window a round magnet so it just sits there a distance away ensuring the spaceship has no effect on the experiment. Then he wafts out gently a large pail of tiny iron filings and dust...
  5. Kupa140

    Analyzing the Force of Two Disk Magnets on a Metal Plate

    The situation is as follows. We have two disk magnets. One is fixed on the ground, table, or surface and has the north pole facing up. Then we have a metal plate fixed on the vertical axis rod or something similar such that it can't move up or down, but only rotate horizontally with as less...
  6. Manuel12

    Magnets with Halbach array in an AC generator

    As a project, I am demonstrating electromagnetic induction by making an AC generator. The magnets I currently have access to are very strong neodymimium countersunk magnets, but I noticed that they utilise a Halbach array. I am aware that this means the magnet has alternating N-S poles spaced...
  7. PlanTer254

    B Magnetic fields attracting two disc-shaped magnets

    I had 2 small magnets in my mouth for distraction while working on something else,and I had this wierd question.the two magnets were not that strong,so just a force was easy to separate them with my teeth.then they would attract to be attached to each other and then the question hit me,the 2...
  8. S

    I Can trains use permanent magnets to be propelled?

    Can a train (e.g. like a maglev train) use a set of permanent magnets (not electromagnets) that somehow can be propelled and maintain at least a constant speed with them? Is this an example of such system...
  9. M

    I Maxwell-Faraday Law & Stealth Magnets: Exploring EMF Induction

    Consider a closed path consisting of a loop of wire with a nonconducting gap that completes the closed path. The wire is threaded through a toroidal permanent magnet, magnetized around the toroid (what I call a stealth magnet). The magnetic flux is considered to be confined to the magnet. The...
  10. Y

    I Exploring the Possibility of Infinite Energy with Magnets

    This is not homework, just a question of curiosity. Something that came to my mind last night. Say I have a magnet and a piece of iron. Say I use it to do weight training exercise. I stick the magnet on the wall and stick the iron on the magnet. Say it takes 100lbs of force to pull the piece of...
  11. X

    I Magnetic field strength of a stack of magnets

    I know that for a single cylindrical neodymium magnet, the formula $$ \displaystyle{\displaylines{B(z)=\frac{μ_0M}{2}(\frac{z}{\sqrt{z^{2}+R^{2}}}-\frac{z-L}{\sqrt{(z-L)^{2}-R^{2}}})}} $$ shows the relationship between the magnetic field strength and the distance between the magnet. I was...
  12. theycallmevirgo

    I The Curious Case of The Impotent Magnets

    I connected some magnets with (single strand) wire and solder in a parallelogram pattern, in the process of making a battery pack. After I was through, it seems they lost a great deal of their force, Identical magnets still attract to them, but unpolarized ferromagnetic objects (like the...
  13. Mr Nobody

    How Can Eddy Current Drag Be Minimized in AC Generators?

    Hello everyone, I'm working on a home project to create AC current, using magnets (AC Generator). I understand the principles of how to generate AC current however, I lack the complex knowledge of the physics side. I have searched and watched various Youtube videos etc, but none of them answer...
  14. Nobody7heGreat

    B Questions on magnets (multiple so I don't spam the forum)

    I want to start this post by saying I don't know much and I'm asking everything here so I don't fill the forum with a million questions. I apologize if this is not how it is done. My questions are... Is it possible for a magnet to be in the shape of a hollow ball?1. Would it pull? push? or...
  15. SBrownJC

    B Do materials surrounding magnets affect how superconductors levitate?

    I'm currently doing an experiment with magnetic levitation but I don't know if my independent variable will even affect my results at all. I am planning on building a rail of magnets and levitating a type 2 superconductor on it. I wanted to change the material surrounding the rail of magnets...
  16. V

    Magnets near a current carrying wire

    Hi! I'm trying to understand electromagnetism. So I had a question: if we place a bar magnets on the low friction surface near vertical wire, then switch on the current, what will happen? As I been told they will align with the magnetic lines, and then nothing will happen. I also suggest that...
  17. 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...
  18. P

    I What's the field strength and pattern rules for bar magnets attached?

    The attached probem tricked me because the answer is apparently D and not A. Presumably because the magnetic field is weaker with 2 bar magnets joined N/S compared to a single bar magnet. So this seems to be a gap in my knowledge as to the resulting strengths of magnets joined together. Are...
  19. G

    B Permanent magnets and energy question

    Hi, I have read some threads on this but I still have some confusion. 1) I get that work has to be done to produce a permanent bar magnet (work to align the dipole moments to give a net field, say in a solenoid/electromagnet) so we can say that the magnet is a store of magnetic potential...
  20. J

    A What is the Lens Addition Equation?

    We all know how quadra-pole and octo-pole magnets are used to accelerate the particles in the longitudinal direction, but what keeps the similarly charged particles constrained in the transverse directions? Especially after the focusing magnets...during the collision you have 10^11 positively...
  21. A

    How can there be neodymium magnets when neodymium is paramagnetic?

    Neodymium is a paramagnetic material, so how do we have a permanent neodymium magnet?
  22. M

    Bar magnet made from smaller opposing bar magnets

    I was wondering if the strength of a bar magnet constructed from smaller magnets would increase if the smaller magnets were placed in an arrangement where the poles were opposing each other. I was able to jam 2 rare Earth magnets together with opposing poles and measured a higher magnetic flux...
  23. Z

    EMF induced by a magnet falling through a coil

    I've been told that if you drop a magnet through a coil the induced emf and flux graphs would look like this: I understand that when the bar magnet is in the middle of the coil the emf induced is zero as flux change in top and bottom is in opposite directions but why is effective flux maximum...
  24. C

    Which of these magnets should have the strongest strength at 10cm?

    Basically, I need to generate the strongest possible field at 10 cm from a circular magnet, in its central axis. I hesitate about what buying. For example, the following magnet has a large diameter of 90mm and is flat, with a suction of 250 kg. This other magnet has a smaller diameter of...
  25. T

    Why do bar magnets have zero velocity after collision?

    I don't understand the reasoning of this question's answer. The answer is velocity = 0 (option A). A while ago, I was told that, since the magnets were held at-rest (before being let go), they must have no velocity after the collision. What about the velocity which they had just before the...
  26. B

    I How many magnets are in the CMS experiment

    Hello! When I google about the CMS magnet I see that there is a 4 T magnet. However in the diagrams with muons, like this one, it seems to be another 2 T magnet beyond that. Where is that placed exactly. I assume it doesn't go around the whole detector, as that would affect the central region...
  27. danielhaish

    Magnetic Attraction: Watching Magnets Move in Unison

    so I toke three magnet, two smell magnet and big one so the big one is attractive both of small onces so it order like -(+-)+ . I toke the small magnet close to the edge of the range magnetic and lift it so the magnetic field is preventing it from falling because the magnet is trying to flip...
  28. SamRoss

    Magnetic attraction / repulsion from the Lorentz force

    I'm trying to understand how the Lorentz force can explain why magnets attract and repel. The explanations that I have found have mostly involved the magnets moving in a way that decreases the forces between them ( ) but I have not been able to find any intuitive explanation involving the...
  29. N

    I Stern-Gerlach w. normal distribution if magnets were more separated?

    Just wondered if the power of mags. is decreased, or they are more separated, don't you get a normal distribution ? (I'm in biology) - would you also not have predicted that w. reasonably strong magnets, they will either end one one side or the other ? Thx a lot!
  30. rayjbryant

    Cylindrical Halbach array with a vertical magnetic field?

    Similar to what is shown here, except the south side would be the weak side of the array. A link to purchase one of these or at least the magnetic field arrangement would be very helpful. Thanks in advance.
  31. S

    Sudden polarity reversal in opposing permanent magnets?

    Hi all, I'm working with a pair of multi-pole neodymium ring magnets (rated ~119lbF) and finding that if the opposing poles are forced together, with the magnets in alignment, that at very close range (may be a millimeter or two apart?) the two magnets will suddenly snap together as if one has...
  32. H

    Permanent magnets and "permeance"

    I have an indoor recumbent exerciser bike that uses a non-contact magnetic "clutch" for resistance. There is permanent-magnetic fulcrum assembly that pivots on a hinge. And a heavy iron flywheel that spins when pedaling. The arc moves toward/away from flywheel based on resistance setting...
  33. Capturing Magnetic Lines of Force in Resin?

    Capturing Magnetic Lines of Force in Resin?

  34. M

    Force between two neodymium permanent magnets

    So I was wondering how I calculate the magnetic force between two magnets. When we learned about magnets, we only covered magnetic fields and electricity (laplace's law) and how electricity can create a B-Field. But how will two B-fields (or magnets) affect each other? Is there a simple formula...
  35. S

    Calculating the flux density between two magnets

    This is for an experiment to deflect a 28 SWG wire between two magnets, 3cm apart, by passing a current through it (example attached). The force on the wire is obviously F = BIL, but the wire will be passing at 1.5cm from each magnet so there will be some significant fall off of B and I can't...
  36. fRod57

    Use of hard drive magnets to build an MHD propulsion ship

    In order to build a small mhd propulsion ship for a physics project, I'm wondering if the magnets we find in hard drives carry enough magnetic field power to function in such an experiment.
  37. F

    Mounting fire / smoke alarms with magnets

    I am building a detachable smoke detector that I'm planning to install with magnets. I am concerned about the safety using this method, because of my knowledge of how magnets react to / affect heat and smoke. I wouldn't risk having the alarm detach itself during a fire, or the magnet to...
  38. L

    Engineering Magnetic Field Question (saturating an iron plate)

    I know that the field inside sample is a combination of the demagnetizing field and whatever applied field you may have. So these two fields together influence how big a field you need in order to magnetize the sample.
  39. K

    I Equation for levitation forces between the magnets and superconductor

    How can I measure the levitation forces between the magnets and a type-II superconductor (YBCO superconductor)?
  40. R

    Fluctuating Magnets: A Guide to Interacting Magnetic Fields

    How would it be possible to fluctuate one magnet between two magnets? Thanks
  41. George-M

    Number of Turns vs. Wire Gauge (BLDC Motor)

    Summary: For the same mass of copper wire, would more turns or greater thickness create a stronger magnetic field from a coil? So I am attempting to make a brush less DC motor, and I am wondering whether the coils would create a greater magnetic force if there are more turns or if the wire is...
  42. A

    Simple experiment with magnets

    I made a little experiment with magnets. I got two small bars of magnets. They obey the usual attraction-repulsion rules by approaching their faces together in various permutation. Accidentally, one of them is broken into two unequal pieces. When I managed to put the two broken pieces side by...
  43. C

    Magnetic saturation and ferrite magnets

    Hi, I believe I understand the basics that permeability of materials is the function of change of flux density with magnetic field. So a non-magnetised material might have a high permeability (easy to increase the magnetic field) while a magnetised mass of the same material might well be close...
  44. Harborseal

    Calculating magnetic field 4 feet away from 2 magnets

    Hi! I'm new here. I took physics back when we calculated pterodactyl drag and I remember what an integral looks like but that's about it. I hope I chose the right prefix. What I'd like to do is find the dimensions of N48 neodymium cylinder magnets that would produce a minimum field strength...
  45. 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...
  46. Dante Meira

    B Do Permanent Magnets Bend Spacetime? Basic Thread

    Basic level thread here. If gravity "bends" the spacetime continuum, do a strong permanent magnet bend spacetime too? I'm no physicist, I'm layman, and I just don't know how this "bending" of spacetime works when a Jumbo jet is in free fall from 10 thousand meters high, pulled by Earth's...
  47. H

    What Magnets are best to demonstrate deceleration?

    Hello I'd like to demonstrate to students how a magnet is slowed when falling through a copper pipe due to generation of magnetic force. What type of magnet should I use? ShouId it be cylindrical or flat? Which way shouId it be magnetized? I have 3/4 inch pipe. Thanks ham1
  48. M

    Understanding Inductrack and Halbach Array in Hyperloop Technology

    Hi, I am currently completing a Gold CREST Award on the Hyperloop Train, and when researching came across a technolofgy called Inductrack. I kind of understand the general concept behind it, however, there's this one paragraph I'm not too sure on and was wondering if someone could explain it...
  49. E

    Magnet system efficiency made from neodymium magnets

    Me and my friend want to make a strong as possible (made from permanent magnets) homemade metal separator for seeds. We are not good in the physics of such level, so we need consultation. We want to try neodymium magnets for our separator. We learned that magnetic flux density could be reached...