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. Q

    Effect of spinning magnets on gauss readings

    My question is about the strength of magnets and how the strength is affected when you spin a magnet. When I use my meter to read the gauss of a permanent magnet I don't get much of a reading at all. However, when I spin the magnet the reading becomes very strong bouncing the needle quite high...
  2. E

    Im curious about magnets Can they be a source of energy or not?

    Greetings fellow members!(New guy!) Before I would start, I've already read a lot of the threads related to "magnets" and "energy". I do undertand the PF forums rules. So please don't lock this thread and say "THIS IS NOT ALLOWED" in reality it is... But maybe its because of the unfortunate...
  3. N

    Can magnets defy the law of energy conservation?

    I'm pretty sure it cannot, but if I put a common bar magnet close to another magnet, they will move towards each other. I don't have much of a background in physics, but it seems to me that the kinetic energy is coming out of...nowhere. I can repeat this experiment as many times as I like but...
  4. R

    What is going on inside my magnets?

    Hi All, I'm currently trying to make a diamagnetic levitation system for manipulating microdroplets for my Ph.D. As I was carefully grinding down my magnets to an appropriate size I noticed that the strength of the field didn't change that much. One magnet before the grinding produced a...
  5. K

    Transfer of Momentum/Kinetic Energy with Magnets

    Homework Statement A horseshoe magnet of mass m stands on one end of a frictionless table. A steel ball bearing of mass m rolls toward the magnet from far away with velocity v and goes through the magnet and beyond. Assume the force of attraction F changes with distance and is the same in...
  6. L

    Building a speaker, have a few questions about the voice coil and magnets

    Hi there, I'm building a speaker for my intro to EE class. We were given ten small washer magnets, some washers, a nut and a bolt. Enameled wire is also provided. My group prototyped a speaker with the following configuration: Voice coil wrapped around a paper tube which fits around the bolt...
  7. M

    Coercivity of Neodymium magnets, could it be demagnetized in an MRI?

    An N45 Grade Neodymium Rare Earth magnet has a remnance (Br) of 1320 mT and Coercive force (Hcj) of 923 kA/m. I am a little confused with the units of Coercive Force, how does A/m relate to Gauss/Tesla? Also, if an N45 magnet was placed inside a 2T MRI, would that be strong enough to...
  8. M

    Guitar Pickups - Shapes of magnets used and their importance

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  9. P

    Exploring the Relationship Between Magnets and Force

    OK i am doing a plan design lab about magnetics so the aim is to investigate how to force between two mangnetics vary with their distances aparts My hypothesis : As the distance between magnetics increases force decrease Can anyone give me points on what to discuss. The discussion part is...
  10. S

    Can magnetic poles have varying strengths?

    I'm quite new here, but here's my question: Is there a way to make one magnetic pole stronger than another?
  11. M

    Reason for dipole and quadrupole magnets in the Large Hadron Collider

    According to Wikipedia, the source of all knowledge, the LHC contains some 1,232 dipole magnets with an additional 392 quadrupole magnets. What is the difference in function between the two types of magnets? How might the effects of magnetic field gradients contribute to the differences...
  12. H

    Magnets generating electricity, non-fixed placements.

    I'm new to the forum so I'm sorry if this question is posted in the wrong place. I have been doing some research on magnetic motors and they seem possible, but I am not talking about the fixed magnet motors where all of the magnets stay in the same position. I found this video where there is a...
  13. J

    Increasing total magnetic moment: permanent magnets ONLY

    This is possibly an engineering, rather than physics, question. (Ooooooooo! Busted!) John picks up a paperclip and notices that it has been (very weakly) magnetized... it attracts other paperclips, but only at ridiculously short distances. John wishes to foster this interesting...
  14. H

    Different magnets with a coil, what are the currents?

    Hi. Can someone please explain/tell me what would be the resulting currents trough the coil in every of the three depicted scenarios in the attached picture, I'm confused here. Would the first and the second drawing produce the same result? Is there any current flow in the third drawing. Thanks.
  15. D

    Unusual question about magnets with same poles.

    Homework Statement A student finds an old magnet at the back of a drawer containing other magnets. He designs an experiment to find out if it is still magnetised. (i) He brings a plotting compass near to end A of the old magnet, as shown in the first part of the image. State the...
  16. R

    Can you use magnets to push other magnets unlimited amount of times?

    As I was bored at the lesson, I did some thinking of my own and magnets always fascinated me, still kinda like black magic. Anyway, i was thinking abou creating this: http://img201.imageshack.us/img201/7476/prepetummobile.jpg I created this in paint as fast as possible so it's not super...
  17. I

    Magnets, Paperclips: Exploring Attraction and Polarization

    So I was goofing off yesterday trying to shoot a magnet off of another magnet because of their similar forces and starting playing with a paperclip. I noticed if I put the paper clip to one magnet, it stuck, as it should. However, when I put the other magnet on the other side of the paper clip...
  18. D

    Can magnets have the same poles?

    Is it possible for a magnet to have same poles? i saw a question in which the compass points the same way in both ends.
  19. P

    Can Magnets Repel Each Other When Charged? Find Out Here!

    Ok, so by no means am i extensively knowledgeable in physics, and the question I'm about to post may or may not have an obvious answer. SO suppose i have two magnets. Obviously, magnets have a negative and a positive end. Naturally the opposite charges attract, and when you try to push like...
  20. C

    Graphing magnetic field of two magnets in 3d space

    I never figured I would encounter a problem as hard as this. Basically, there are two magnets of varying strength at 2 different x, y, z coordinates. I need to come up with function(s) to graph the field in 3d space. Or, at least find the x,y,z point where the two fields cancel out (if they...
  21. D

    Magnetism & Electricity (2 magnets - Field)

    I am trying to calculate the output voltage for 1 coil in an axial generator/altenator I have 2 magnets with Br Max 13200 Gauss on opposing sides of the rotor (N-S facing), The coil is between them on stator. Using faradays equations what is the effective Br (Gauss/Tesla) that should be used...
  22. M

    Magnets/ Magnetic fields energy storage?

    Very strong magnets like neodymium can create a very powerful force! I wonder the amount of energy supplied when there created to be magnetized, in a sense don't they store energy and it is converted"demagnetized" over time? It came from the electricity used to create that magnetic field...
  23. N

    How is momentum transfered between magnets?

    Hi, I was wondering how is momentum transferred between magnets? Basically I know that magnets produce a magnetic field and when two magnets that are opposing (N-N or S-S), they cause each one to move away from the other one. I also know that the momentum is conserved because one moves one way...
  24. S

    Force between two permanent magnets at an angle

    Hay all, first post (ohai2u! ^_^), so hope this is in the right place. I feel really stupid for having to ask this, because I'm sure the answer is really trivial, but here we go... Ok so, imagine the scene - You have two permanent magnets on a table. Let's (for argument's sake) call these...
  25. K

    Question about magnets repulsion

    Hello, Imagine I have 2 magnets and they are repelling each other. Then I add a piece of iron in between them. Would they be attracted to the piece of iron? Yes I could just check for myself, but I'm getting my first magnets shipment only next week and I would like to start working on my...
  26. R

    Strength of magnets in an array

    Hello all, I need to make a magnetic surface using neodymium disc magnets... the purpose for the surface is to hold on to a sheet of ferrous material, as strongly as possible. I tend to want to assume that a checkerboard array would be best... alternating the poles of the magnets in the...
  27. C

    Can Magnets Really Produce Endless Energy?

    This appears to spin forever. Isn't it possible to build it big enough to generate a reasonable amount of power? [Link to Perpetual Motion Machine Deleted]
  28. M

    Is it safe to use electronics on a maglev train or a magnetically levitated bed?

    Forgive me for being slow; We have always been told to keep magnets away from electronics, especially computers. Some places in the world have these Maglev trains, and it would seem to me that the magnetic force required to levitate 200 tons would destroy any electronics you would bring...
  29. B

    Ceramic Magnets and their durability in temperature fluctuations

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  30. Chemicist

    If Cars Had Magnets: What Would Happen?

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  31. D

    Understanding Flux Between Two Magnets

    I know that when there's a magnet next to a piece of iron, the former's flux density just travels across the air gap between them provided it's small enough. But what happens when there's two magnets next to each other? I know B follows the superposition principle, so do their flux densities...
  32. M

    Strong motor using permanent magnets?

    Greetings all. I was wondering if I could build a low energy consuming but a powerful motor using neodymium magnets and a AC electromagnet(for switching poles N>S>N>S,etc...) The magnetic field created by the electromagnet could potentially attract a large and stronge neodymium magnet in...
  33. M

    Magnetic Pull/Repelling force of magnets?

    Hi all, I bought these neodymium magnets that all have a pull force of: 20.86 lbs If the pull force is equaled to that will the repelling force be the same as well? Since their both the same.
  34. W

    Forces between to permanent magnets

    Forces between two permanent magnets I am new to the concept of magnetic field strength and the behavior of field lines etc, so please correct me if any of my thinking is incorrect. I want to increase the force between two permanent magnets that are at a distance apart. At the moment due to...
  35. L

    Magnets or EMF in car bumpers to protect from fender bender

    Hi I am new to the forums. I am sure I have found the right place for help with an idea I have been working on for a while. First off please forgive my lack of physics knowledge. What amount of magnetic force would I need to stop or dramaticallyjust deccelarate a standard size 5000lbs car going...
  36. S

    Could I use electro magnets to repulse the earths magnetic field to levitate?

    I have this idea that I could use some electromagents that wen I run current through will repulse the Earth's magnetic field and that the higher voltage(or whatever electrical unti I decide to use) would send and object farther away from the ground and that the lower current would bring it...
  37. H

    Can magnets act as accelerators to certain objects?

    Hallo everyone! I was wondering is it possibile to use magnetic attraction/repulsion to increase speed or rotational speed of an object? this video is a quick illustration of what I mean. If it possibile to use magnets as "accelerators" how is it possibile? from magnetic fields? or...
  38. C

    Long term magnetic repulsion with permenant magnets?

    i have a set of neodynium magnets which i am using for a magnetic levitation project... will the constant exposure to an opposing magnetic field weaken the magnets over time? are 'permenant' magnets really permenant?
  39. U

    Looking for some cool magnets / gadgets

    Hello all :) I'm look for some cool things to look at or buy, I'm after mainly desk accessories such as swinging pendulums or something magnetic. I have seen some videos a while ago about a kind of magnet gadget which you could place a copper penny inside and it will just float in between the...
  40. S

    How Does Magnet Quantity Affect Descent Speed in a Copper Pipe?

    Homework Statement So i had to make a thesis and hypothesis for this lab where i have magnets in bundles all of the same mass some with more magnets in them than others. I have to do a lab and an analysis of how it relates to forces and energy and work Homework Equations Does the...
  41. N

    Force between two cylindrical magnets

    Hello, I'm a high school senior and I'm trying to find an equation to calculate the force in the x direction between two identical N35 Neodymium magnets given a certain position relative to one another (see attached .jpg). N35 cylinder magnets Dimensions: 4.5 mm (height) 5 mm...
  42. H

    How Does Cooling Affect the Longevity and Strength of Neodymium Magnets?

    Hallo everyone! As you all know one of the strongest rare-earth magnet is Neodymium. I was wondering... under very cooled temperatures their magnetism will last for a longer time as usual and their magnetic field will be stronger than before too! How long do you think it could last? I mean...
  43. X

    Dropping two magnets through a copper tube

    Hi, In class we were discussing the effects of a two bar magnets being dropped through a copper tube at around the same time, with the same pole facing towards each other, so that the two magnets repel - would the magnets fall through the tube faster or slower than if only one was dropped...
  44. R

    How do magnets pull things if magnetic forces are incapable of doing work?

    When a magnet pulls a paperclip, what exactly is doing work on the paperclip? It cannot be a magnetic force can it? I thought it was a very strong statement that I read in my intro physics book and even Griffiths(pg. 207) that magnetic forces do no work. So what is responsible for accelerating a...
  45. V

    Simulating toy magnet balls ? (eg: Zen magnets)

    I'd like to simulate the interaction between these magnetic balls on my computer. I suppose they are magnetic dipoles, how would I go about finding out the forces applying between 2 of them in a specific configuration ? Do I need to find the magnetic field and then apply the Lorentz force...
  46. G

    Electromagnetic Piston using a holding magnet and permanent magnets?

    Dear all - I am new here so please be gentle :smile: I have searched the site for a few days but alas still have a few questions on something i am hoping to make...so with your kind help - here we go! I am looking to make a type of electromagnetic piston, basically i want to have an...
  47. C

    Linking current-carrying wires to magnets

    This may be an obvious question but I have no idea: How can anyone link current-carrying wires (solenoids) and its formulae, to magnets?! All I've researched so far points out that magnets have their own stable magnetic field, attributed to the alignment of spins of the electrons of the atoms...
  48. A

    How Do Magnets Work At an Atomic Level (Motion of Charged Bodies)?

    I'm a year 12 physics student and I have a keen interest in the inner workings of a magnet. I know that magnetic fields are created by the motion of charged bodies. 1. Is this somehow related to the how magnets create their fields, within their structure at an atomic level? I've heard that...
  49. C

    Are two magnets twice as strong as one?

    Hi there, I am having trouble with a project I am working on... hopefully someone will be able to help me. :) I have some neodymium magnets that are rated as having a ”pull" strength of 3.1kg each, I am assuming that this means that you can attach it to a metallic surface and it would take...
  50. B

    Energy needed to connect two repulsive magnets

    I have a problem that states how much energy would it take to make two repulsive magnets touch if the magnetic repulsive force is 51.7kg per magnet and the mass of magnet 0.515kg and the magnets are 2cm apart. This is the way I tried to solve the problem using the formula for work. w= f * d...
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