magnets Definition and Topics - 64 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. 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...
  2. 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...
  3. 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.
  4. Capturing Magnetic Lines of Force in Resin?

    Capturing Magnetic Lines of Force in Resin?

  5. 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...
  6. 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.
  7. 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...
  8. M

    Inductrack and Halbach Array

    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...
  9. F

    How scientists ensured this fundamental property of magnets?

    Firstly, please note that I am talking about the period BEFORE electricity and magnetism were unified. So I am NOT seeking for answers based on Ampere atomic current model of magnets. I have read the following statement about the property of magnets at two different places. One from here: and...
  10. YoungPhysicist

    Do magnets lose strength by pulling them apart?

    When two magnets already sticked to each other being pulled apart, energy is applied, so I assume that the energy is stored like some sort of potential energy which will be turned back into kinetic energy when they accelerate towards each other to stick back together. So the magnet itself...
  11. J

    Why do more magnets affect how long a homopolar motor spins?

    Hi All, My daughter did a science experiment on homopolar motors. The only variable was the number of magnets on each motor. We found out through the experiment that the more magnets we attached to the motor, the longer it spun before the battery died. I'm assuming it has to do with the...
  12. Alex Schmitt

    How to make a short range, remote-controlled electromagnet?

    I am currently working on my high school's upcoming production of Beauty and the Beast. In the musical, there is a rose which loses petals at specific moments in the script that represent the castle's inhabitants slowly becoming less human. I figured that one of the best ways to do this remotely...
  13. Cathr

    How to predict the movement of a magnet in a magnetic field?

    Can we predict the movement of a magnet in a uniform magnetic field using Maxwell's equations? What if the magnetic field is variable, for example if we have two magnets moving in a reference frame? Thank you for any answers and I wish you a Merry Christmas! :)
  14. R

    Magnetic Force Applied to An Object @ d (0,n) (Rail gun on Mars)

    So long story short, I'm trying to write a scientifically accurate short story/animation thing and it revolves around a mass driver: it's a giant and deep hole on mars with a magnet on the bottom or sides or something and fires packets of objects to earth at breathtaking speeds (4.66 million...
  15. S

    Magnetic materials

    I am putting together a hands on activity for ninth graders, which will include testing different materials to determine whether they are attracted to a magnet. I have collected fasteners (screws, nails, bolts), and surprised that the fasteners I purchased labeled "zinc" are attracted to the...
  16. Sveral

    Cutting magnets without losing magnetization (Curie temperature issue)

    Hello, I wanted to know, if someone knows of a realistic option of, how to cut barrium ferrite magnets without using a rock saw and without demagnetizing the magnet obviously? Thanks in advance everyone.
  17. K

    Inducing electricity w/ moving piece of metal, static magnet

    Hi! I'm curious to know, whether it is possible to produce electricity by moving a piece of metal over a magnet (i.e a immobile magnet and a moving piece of metal close to the magnet), and how this would be done in practice.
  18. U

    Need explanation about magnetic forces

    Hi, I saw this video and I can't explain why the magnet is propelled to the end of the coil with such a huge force. Can someone explain it in clear terms. I also tried to use Flemings left hand (or right hand) rule but it did not give me a satisfactory answer. Thanks, SM
  19. gammzy98

    How to use magnets to float an object (Diagram)

    Hey everyone, I have been doing some research in regards to floating an object, and possibly have it rotate. I am thinking magnetism is the way to accomplish this, but if anyone else knows another method I would love to hear it. I created a simple diagram on what I am trying to accomplish...
  20. AHashemi

    Magnetic levitated electric wire

    Hi I'm thinking about making an instrument to show the force on a wire carrying electric current for students in lab. A normal wire which levitates from ground after it has current flowing in it. We have the following equations F = ILBsin(a) W = ALg 'A' being the mass of unit length of the...
  21. Alanay

    Can magnets on a cylindrical object be used for projectiles?

    What I mean is if I have 2 cylinder objects made out of a light wood for example with 6 or so magnets on either face spread evenly and another magnet behind it causing it to spin could it generate a good amount of torque to shoot a small projectile between the two cylinders. To give you a better...
  22. Alanay

    Can magnets be used to send a metal ball through a pipe?

    To elaborate more on my question: Is it possible to send metal balls through a pipe with magnets arranged a certain way which could hit a target with force. I've seen something similar done before but I think the ball was also a magnet, is that the only way possible?
  23. B

    Flux Density, B, of a Cylindrical Magent

    Hi, I'm trying to calculate the flux density of a magnet, I can get all but one of the values needed to calculate it. Does anyone know how/where to get the z(distance from a pole face on the symmetrical axis) value?
  24. Ken H

    Energy imparted to an ion by a magnetic field

    Basically my question is: if an anion is placed by the negative poll of a magnet will it push on the particle?
  25. 1

    Help designing/finding a vendor for this magnetic field

    I need help find a electromagnet suitable for this http://imgur.com/a/vkm4T Each electromagnet (the 3 in the center) needs a repelling force of about 20 to 40lbf. I stupidly bought these from amazon http://a.co/aSftIat. Its a holding electromagnet so the N and S poles are essentially on the same...
  26. N

    Interesting experiment about the attraction between two magnets

    We know that the attractive force between the opposing poles of identical permanent magnets is a product of their field strength and that the total force diminishes as the distance between them increases. If we assumed the magnets to be point entities, the formulation is the same as that for...
  27. 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...
  28. Brendan Staley

    Creating an electromagnetic board for levitation

    I am wondering if it is at all possible to create a magnetic board which is capable of repelling magnets. I am looking up magnetic levitation and would like to make a DIY version at home. Any tips/tricks to make this. Thanks in advance!
  29. V

    Energy used to bring magnets together

    If you want 2 magnets to touch when the poles are the same . Would it matter how you do it,moving them vertically towards each other or horizontally? Does it mater how you get them together and separate them? Would it use the same energy to join them horizontally as they would make repealing...
  30. 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?
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