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. J

    Where do magnets get their energy?

    It seems like magnets have an enormous supply of energy. Where does a magnets energy come from? It almost seems like it has a never ending supply of it. Think of this thought experiment. A permanent magnet is suspended 1m away from the floor. A steel ball is placed onto the floor under the...
  2. P

    Magnetization currents of Magnets with μ_r close to 1

    Neodymium-Iron-Boron magnets have a relative magnetic permeability of 1.05. According to the formula: B = μ0 * (H + M) Both the magnetizing field H and the magnetization M contribute to the magnetic field B. The magnetization M has sources and sinks, so therefore it follows from Maxwell's...
  3. Asmaa Mohammad

    Using two electromagnets to study self-inductance

    Hi, I study physics and I know what the concept self-inductance means, and in one of my study books, a figure like this was used to explain the self inductance in a coil As shown in the figure, two electromagnets are connected together and the current is passing through them and would produce a...
  4. M

    Lenz's Law in action with different length magnets

    Hi, I was doing an experiment with Neodymium magnets and a long copper pipe (3cm internal diameter) to see Lenz's Law in action. At first I used a long bar magnet (about 15cm long) and there was little resistance to the magnet falling through the pipe. It was only slightly slower than a...
  5. mohau tshekoeng

    Is it possible to calculate the magnetic force between magnets?

    Hello I am a a grade 11 learner and I am trying by all means to calculate force between magnets. I know that the strength of a magnetic field is determined by the size of the magnet.
  6. Low-Q

    Magnetization and Demagnetization in Magnetic Materials

    Hi, I have been asked how many times a magnet can magnetize a magnetic material before itself get demagnitized. The example in hand was the question about a strong neodymium magnet that accidently ruined a ferrite magnet. The next question was then why this neodymium magnet appears to not lose...
  7. Brendan Staley

    Creating an electromagnetic board for levitation

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  8. V

    Energy used to bring magnets together

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  9. G

    Is there such thing as magnetic interference?

    Say I place a magnet on a table, and I have a metal in close proximity. Will its magnetic field change due to the presence of this metal, however minute? What if I had another magnet or the table itself is made of materials the magnet is slightly attracted to? Does this phenomenon even exist?
  10. G

    How Do Magnets Really Work? Investigating the Complex Phenomenon of Magnetism

    Hello PF! I am writing a scientific report about magnets, but have really no clue how magnets actually work? Research has yielded a few ideas, specifically from here and here. However, sometimes (in iron, nickel, and cobalt for example) you’ll have one or more un-paired electrons. The...
  11. K

    Magnetic field direction on Halbach array?

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  12. G

    Magnet Experiment: Investigating Force & Distance

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  13. A

    Light, thin but strong magnet?

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  14. D

    Magnets in space -- AKA vacuum

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  15. mzideefixe

    Can magnets be used to keep something at a certain distance?

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  16. V

    Piggot type generator, Magnets

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  17. M

    How to calculate force caused by magnets?

    I am trying to calculate the forces between a simple sphere neodymium magnet on other iron surfaces and magnets. I did a lot of research but still not sure what equation to use or how to apply them. I found the following equations here (https://en.wikipedia.org/wiki/Force_between_magnets) F =...
  18. S

    Why does heating a magnet make it less magnetized?

    I'm talking about how like the atoms expand and the electrons get farther away from the nucleus. This might be a stupid question but how does that make it less magnetic? Like what do the electrons being farther away have to do with how strong the magnet is?
  19. Akmalidin

    Why permanent magnets are not used in Synchronous Motor?

    I am Telecommunication student but interested in motors.Especially, power generators.I was wondering why permanent magnets are not used in synchronous motor's stator or rotor? Is induction motor more efficient than permanent magnet used motor? What about in power plant generators, do they use...
  20. Hons K Wyn

    Magnets and coils configuration for electricity generation

    My dad is working on a project where he intends to convert mechanical into electrical energy, and he was wondering if a particular magnet and coil configuration works for electricity generation. And if it does, how are the voltage and current calculated. Lets say: The coils have a diameter of...
  21. H

    Electromagnetic induction question, coils and magnets

    Say you have a coil connected in a closed circuit. You then move a magnet inside of the coil and it remains stationary inside of the coil. Is the magnet, even though it is stationary, still inducing an emf in the coil or is it not? I'm guessing it doesn't induce an emf in the coil because...
  22. jeisson botache

    Seismic isolator based on magnetic forces

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  23. K

    Do # of magnets affect the time for a metal"s Curie point?

    I'm doing an experiment regarding Nickel's time for a Curie point. The nickel will be connected to a wire on a pendulum and will be attracted to a neodymium magnet, but it will not be touching it. A candle will be placed in front of the magnet so that when the nickel moves toward the magnet as...
  24. O

    Ferromagnetism - thought problem

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  25. H

    Check logic for Watts calculation

    Thanks to anyone kind enough to help check my logic. Using 13 gauge copper wire and a magnet I can generate .05 watt every time the magnet passes the coil (according to the voltmeter). Am I correct in assuming that if the magnet passes the coil 60 times a minute, then (.05 watts X 60rpm X 60...
  26. alexandria

    Electric DC motor, commutator, carbon brushes, and magnets

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  27. KidThinkPhysics

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  28. G

    Practicality of building large size magnets

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  29. J

    Energy expended during magnetic levitation?

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  30. B

    Basic question about Halbach magnet array

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  31. JGBuck94

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  32. K

    Question ιn Physics about moving magnets?

    Hi, today i had exams in Physics and my Professor as an extra points question was asking the following question. We have 2 magnets, one is named Alpha with dimensions 100 cm length, 70 cm width and 2 cm thickness (100x70x2) and the other one is named Omega (200x100x5). Alpha is moving...
  33. C

    New with a question

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  34. P

    Field Energy of Permanent Magnets vs. Magnetic Monopoles

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  35. ardakaraca

    How does a square shaped magnet act like a ring magnet?

    Hi, I'm working with a magnetic levitron project and I've borrowed a professional levitron to see how it works. When I remove the back cap, unexpectedly I saw a square shaped magnet instead of ring magnet. But it acts like almost a ring magnet. I'll explain the difference with images below. At...
  36. 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...
  37. itoero

    Demagnetizing Neodymium magnets in a candle flame?

    Is it possible to partly demagnetize neodymium magnets in the flame of a candle? Those magnets are made up of Neodymium, Iron and Borium. They have a Nickel-Copper-Nickel coating. The Curie temperature for Neodymium magnets is 310-400°C. Neodymium (magnetic powder) burns but does the coating...
  38. Charles Link

    On the Pole Method of Magnetostatics and Permanent Magnets

    The pole method of magnetostatics is presented in many E&M textbooks, particularly the older ones, to do computations in magnetostatics and even to try to explain permanent magnets. An equation that arises in the pole method is B=H+4*pi*M (c.g.s. units), where H consists of contributions...
  39. H

    Refrigerator magnets with four poles apiece

    I bought a couple of bar magnets at the local hardware store. They were acting so strangely. I couldn't figure out where the poles were. Finally I realized each magnet had four poles! They weren't quadropolar, rather half of each bar was magnetized one way and the other half the other way...
  40. GuhaGubindam

    Which direction does a charged particle move in a magnetic field?

    I understand that a cathode ray will be attracted to one pole of a magnet, while being repelled away by the other. The cathode ray, being electrons and thus negatively charged, must definitely be attracted by the positive pole of the magnet, while being repelled by the negative pole of the...
  41. N

    Changing motor speed with external magnets

    In the below video it is shown that rpm is increasing by using external magnetic field . can i know on which principle it is based on?
  42. N

    External magnets to PMDC motor

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  43. T

    Magnets - looking for help with school project

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  44. J

    How can you move with magnets?

    How can you make something move forward or backwards with magnets. I didn't got it in here : Minute : 5:00 forward It said how the train move but i don't understand why it moves. It makes no sense for me because it is the same force that keeps the train floating?
  45. F

    The force and torque between two permanent magnets?

    Hi all =) I am interested to find the forces and torques between two (diametrically magnetized) cylindrical permanent magnets (PMs) placed within a vicinity, as shown below: The NdFeB PMs placed beside one another with a distance, d. Both are rotated by independent external sources (I have...
  46. N

    Could one use magnets to create friction and thrust

    if I had a motor with a pendulum and a magnet at the end of it, and attached to this motor was a frame holding a another magnet that is close enough to the pendulum to exert force on it when it is horizontally positioned would that force make friction with the inside of the motor creating thrust...
  47. A

    How Do Vortex States in Biological Magnets Impact Ferrimagnetic Behavior?

    Hi, I have been reading this fascinating paper here: http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4484.html I'm struggling with some of the biophysics, and it would be great to get a discussion going. In particular, I was struggling with the statements where it says "The two...
  48. M

    How Do Bar Magnets Create Zero Magnetic Field at Point P?

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  49. moenste

    2 magnets falling, one through a metal ring, which is faster

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  50. Fededevi

    Magnetic circuits and Magnetization

    From my little understanding of magnetism and the magnetization process, in order to magnetize a magnet it is better to have a closed magnetic circuit. But how does an air gap affects the magnetization "strength"?Example: Assume that we have a unmagnetized horsehoe magnet with a coil around it...
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