Magnet Definition and 912 Threads

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. R

    Causing levitating magnet rotation

    I have a device like this one: http://www.youtube.com/watch?v=kA_hw_lY-OY (All of them work the same) Here's an image: I want to make it spin without touching it with hands. I tried using magnets of several kinds, and tried to put them in many places around it but it didn't make it...
  2. A

    How does a magnet create its magnetic field.?

    how does a magnet create its magnetic field.?? we know, magnetic field is a consequence of velocity attained by a charge..In case of magnet(naturally formed) how do they have magnetic field around them..If it is due to velocity of electrons in it,then all particles should have magnetic field to...
  3. M

    Can a permanent magnet motor generate unlimited energy?

    I am studying Mechanical Engineering at college, so please forgive me for any assumptions I make. I know (been told) that magnets are used to convert mechanical energy into electrical energy. And have no energy of their own. I have been thinking why a magnetic generator powering it self will...
  4. R

    Nature of Coil and magnet fields?

    I find it difficult to visualise how the magnetic field generated by a coil can be the same as the field of a permanent magnet. Are the magnetic fields the same or is it just that the effects are the same in that they both attract iron or magnets in the same fashion? Visualising the field...
  5. X

    Permanent Magnet vs. Electromagnet: What's the Difference?

    My Question is same as the title of this thread.. and Secondly.. what is the difference between electromagnet and magnet??
  6. J

    Can a Neodymium Magnet be used as an electromagnet?

    Hi, I would like to know if Neodymium Magnets can be used as an electromagnetic magnet. The idea is to get a Neodymium Magnet and add DC voltage to do the Gauss Law. The college project is make a very powerful electromagnet, so I thought adding the most powerfull magnet and the some DC...
  7. A

    Electric field produced by a magnet

    Hello, I was just wondering how is it that a steady magnetic flux (stationary magnetic field) is capable of inducing a current in super conductor, as in the Meissner effect, where as a changing magnetic flux (moving field) is required in the case of a normal conductor.
  8. M

    The uniqueness of a magnet? Let me tell you why.

    In all of the things that we've discovered have you ever found something as amazing like a magnet? An object that can attract/repel (by using force!) on its own similar other magnets or metals. The only object present to withhold a significant amount (depending on type,size,etc...) of force...
  9. C

    Magnet in a Pipe: Meisner Effect?

    Lets say I have a superconducting pipe that is infinitely long. Now I place a magnet in the pipe, will the magnet stay placed in the pipe due to the meisner effect? And the magnet is in a Constant gravitational field. And the pipe is vertical in the G field.
  10. P

    Magnet moved through copper ring

    Homework Statement The figure shows a ring of copper with its plane perpendicular to the axis of the nearby rod-shaped magnet. For each of the situations described below, indicate whether there will or will not be a current induced in the ring and justify your reasoning, drawing pictures if...
  11. P

    What is the acceleration of a magnet when dropped towards a copper loop?

    Homework Statement A magnet is dropped towards a loop of copper .the acceleration of magnet will be ? Homework Equations The Attempt at a Solution less than g ,because copper will oppose the relevant pole(im not sure why?)
  12. M

    NIB Magnet Dropped in a Cu tube - Forces

    Homework Statement I'm trying to figure out and explanation as to why a strong magnet drops so slowly through a non-magnetic but conducting Cu tube. The attached diagram shows the original B field, induced Eddy currents, and secondary B field as a result of those Eddy currents, but I can't...
  13. P

    Question about a magnet and normal force.

    Lets assume that liquid superconductors exist. Now I place a magnet above a pool of the liquid. Now will the surface of the liquid remain level or will it appear to have dent in it. I am not sure I kind of back and forth in my head.
  14. R

    Does a Magnet on a Fridge Affect Electricity?

    Dear Experts Could you tell me does putting magnets on fridge doors consume more electricity or no effect? Thanks. Regards Ramone
  15. M

    Magnetic layers in a spherical magnet.

    Correct me if I'm wrong about anything. I've browsed here many times, but this is my first post. I was thinking about Prince Rupert's Drop (http://en.wikipedia.org/wiki/Prince_Rupert's_Drop) and I wondered about spherical magnets. Prince Rupert's Drop is able to withstand high magnitudes of...
  16. S

    Magnetic field of magnet and its defination

    When we consider a magnet, usually we perceive the field lines to come out of the north pole. But since the poles of a magnet is actually just a man-defined thing, so actually the magnetic field doesn't emerge from the north but it's a constant loop. So when i draw the magnetic field of a bar...
  17. Undacuva

    Power required to reverse an electropermanent magnet

    Hi, I need to know how to calculate the power level and pulse width required to revers the polarity of a rod or bar shaped alnico magnet, depending on the width. I also don't know whether to use AC or DC power. I'm prototyping an invention and it needs to be as power efficient as possible.
  18. C

    Magnetic force lost when you break a magnet?

    if you have a magnet that pulls 40lbs of force if you broke that into 2 how much force will each magnet pull. i have some neodymium magnets from hardrives and i want to break them up but i want to know if that's gunna make them lose a lot of force. anyone know the formula for calculating...
  19. Crazymechanic

    Magnet on Metal Wall: Exploring the Work of Magnetic Fields

    Hi a simple question that struck my mind.Let's imagine a ferrite magnet from a old loudspeaker now let's put that magnet on a metal wall , or door , the magnet holds to the metal vertically and any other material put similar would just fall off so t seems to me that the magnet or the magnetic...
  20. Y

    Is Electricity Generated when a Magnet Falls Through a Copper Pipe?

    The title is pretty self-explanatory. I know the speed of the falling magnet is much slower in a copper pipe, but since the magnetic field moves, is there still some electricity generated in the process, even though the speed isn't great? Thanks!
  21. R

    Magnet Moving inside Copper Tube and Current Direction(s?)

    Hi, this is my first post here. I know that, according to Lenz's law, if you drop a magnet inside a copper tube and let it fall, its movement will cause an induced current, which will slow it down in turn. However, my drawings make me believe that the direction of such current should be one...
  22. J

    Determing field gradient of Stern-Gerlach magnet

    Homework Statement Determine the field gradient of a 50-cm-long Stern-Gerlach magnet (d1) that would produce a 1-mm separation at the detector between spin-up and spin-down silver atoms that are emitted from an oven at T=1500. Assume the detector is located 50 cm from the magnet (d2). Note...
  23. A

    Are Permanent Magnet Machines Inefficient at Lower Power Levels?

    Hi, when a perment magnet machine is designed for a particular power but is operated at a much lower power, is it inefficient as with induction machines? Thanks
  24. T

    Magnet repulsion distance calculation

    hey, so let's say i have 2 Neodymium magnets with a pull force of 10 pounds and set them at a position where they repell themselves. so my question is: how can i know in what distance will the top magnet be from the other one? if there's and equation for that or an explanation, please tell...
  25. S

    Induced emf when dropping a magnet into a solenoid

    I am having some trouble understanding why and how the emf changes when a bar magnet is dropped into a solenoid. As the magnet moves down (have not entered the solenoid yet) it experences an increase in magnetic field. As it enters the magnet it experiences an increase in magnetic still until...
  26. J

    Velocity of a magnet traveling in a magnetic field

    So if we can one large not moving magnet and a small magnet that is attracted to the large magnet we know that ( http://en.wikipedia.org/wiki/Magnet ) F = μ qm1 qm2 /(4 pi r^2). Here the small magnet is traveling in a straight line because it is attracted by the large magnet. Where F is...
  27. M

    Electron Radius in a Bending Magnet

    Problem: 15 MeV electrons enter a bending magnet with a magnetic field of .7 tesla. What is the radius of the path of electrons? Equation: r = mV/Bq B = .7 tesla q = 1.6 x 10^-19 C My problem here is that I don't know how to find the velocity of the electron for this...
  28. E

    Calculating magnetic field as a function of magnet size

    I want to determine how large a magnet I need in order to get a given field a certain distance away from the surface. An N48 neodymium magnet has a Bremanence of ~1.47T. How does the physical size of the magnet affect the field a given distance away...
  29. B

    Subjecting a Magnetorheological Fluid to both poles of a magnet?

    Hi, I'm new here, but it seems there are some pretty intellectual people running around. I was researching magnetorheological fluids, simply because I came across them and thought they were really interesting. I learned that when they are subjected to a magnetic field, the iron particles in...
  30. M

    What happens to a permanent magnet inside a electromagnetic toroid?

    Suppose a permanent bar-magnet is placed inside a toroid/torus and the toroid is then completed and power applied. How will the magnet move? Will it move?
  31. M

    Can a magnet's magnetic field perform work on another magnet?

    Hallo everyone, Can a magnet do work on another magnet? (I believe it can. Just wanted to make sure.) What formula's do you use to support you're answer? Finally, I know that magnetic field can not do ANY work on a free charge based on Lorentz force so no need to reference that. Regards, Miyz.
  32. G

    Static magnet attached to a fridge

    Hi all, I had a thought earlier about magnetic forces. If there's a magnet attached (at rest) to my fridge, then there is a magnetic force on the magnet towards the fridge and vice-versa. This force stops the magnet from falling because of the frictional force between the magnet and the...
  33. C

    Restoring the magnetic-flux of a magnet

    How do you go about restoring the magnetic-flux of a horseshoe magnet that has lost all its' magnetic-flux? The magnet was originally weak and was sent to a company to have the magnetisim restored and when returned, all magnetic-flux was gone, as if it had been degaussed.
  34. L

    Current-carrying Wire in a Circular Magnet

    Homework Statement Determine the direction of the force acting on the current-carrying wire in the magnetic field. Homework Equations Lenz's Law The Attempt at a Solution This problem confuses me as the current is moving in a circular loop. However, I tried to use Lenz's Law and...
  35. T

    Coil design and magnet orientation in a unique generator

    First, I am not an electrical engineer - I am a hobbyist building a prototype linear-stlye generator based on an idea I had which, for various reasons, cannot be built with magnets that pass completely inside of coil(s) like most of the ones I have seen described for wave energy capture and...
  36. K

    Orientation of magnet relative to coil and it's effect on inductance

    Say I have a coil that is stationary and I have magnets that move past it in a fashion similar to the example in this video: . What is the optimum orientation of the magnet and coil to induce the most current? I know I will want to optimize the rate of change of magnetic flux through the coil as...
  37. T

    What Battery Voltage is Optimal for My Self-Built Electro Magnet?

    This might be too simple of a question but i am building an electro magnet and breaking down all of the components for sheer practice. when i measure my coils resistance it came to roughly between .9Ω and 1.3Ω... what battery (what voltage should i use to get the most power from my magnet and...
  38. D

    Magnet moving in a long long solenoid

    I have heard that when a magnet is moving completely inside a solenoid, there will be no induced emf. Is that true ? Personally, I think even the magnet is moving inside a solenoid with speed v, there will still be induced emf. Assume a magnet is moving inside a solenoid from left to right...
  39. G

    Quantum Falling Magnet: Lenz's Law Demo?

    I take it that it would be ok that in the classic demonstration of Lenz's law with the falling magnet, to replace the magnet with some quantum particle of non-zero magnetic moment and make the tubing a solenoid in order to generate a current as the particle fell? Obviously the current would be...
  40. P

    Measurement of spin due to the force on a magnet

    Can we measure the spin of a particle by measuring the force on a Magnet? I wish to consider a modified stern gerlach like apparatus where a Magnet of mass M is attached to a spring. Can we measure Spin of the particle by studying the deflection of the magnet? Even if it is possible, I can...
  41. D

    How do you calculate the Magnetic Moment of a Permanent Magnet?

    Hey! I am trying to find a permanent AlNiCo magnet with a magnetic moment of 0.06Am^2. However, most magnet data sheets do not list the magnetic moment of their magnet. Often they list the Magnetic field in Tesla or the moment in Vs*cm. How can I convert this data into the magnetic moment...
  42. G

    Spin property as a tiny magnet

    As a preface to a different question, it is valid to think of the property of spin of elementary and related particles as basically just tiny magnets, right?
  43. parazit

    COMSOL Multiphysics : Bending -Dipole- Magnet Design

    Hi friends. I am so new with Comsol software to design something but I wonder, if it is possible to desing a bending magnet (dipole) and simulate the motions of electrons ? I really would like to do this. Please give me a hand,help me to handle and try to do one together. Best.
  44. A

    Relationship between the pulling force and the magnetic field of a magnet

    So I recently bought a couple of magnets for an experiment and the website lists the pulling force of the magnet as 24 pounds. I am pretty sure there is a relationship between the pull force and the magnetic field. Can someone please help? Thank you!
  45. P

    Special Repelling Magnet Shoes

    Hello, I am new to the forums, my name is Brandon. I have just recently graduated high school. I graduated from my physics class with a 97% for the year! yay! But off to my question... I have been thinking of a cool project that involved 4 neodymium magnets and using the repulsion force...
  46. D

    Why doesn't magnet + gravity = energy?

    Hello, Please forgive my ignorance. I am not a mechanical engineer or physicist by degree or trade (I am a software engineer). I am well aware that perpetual motion is a violation of conservation, and that (even if it were not a violation) perpetual devices could not perform work. My...
  47. A

    Field at the center of a toroidal permanent magnet

    I'd like to make a strong (~0.5 T) solenoidal field with a permanent magnet for a Faraday rotation experiment. If I take an ordinary cylindrical permanent magnet (with an axial field) and drill a hole down the center of it. What's the field deep inside at the center of the hole? Some of the flux...
  48. W

    Energy cost during neodymium magnet production?

    Pretty straight forward. Whats the amount of energy needed to create a neodymium magnet? What's the cost ratio? These magnets are expensive, but is the amount of energy needed to create them very high (2Kw)? Or is it still pretty reasonable? Does anyone have a link with accurate estimations?
  49. C

    Can an Electro-Permanent Magnet Work as a Temporary Lifting Device?

    So I am trying to come up with a magnet parts lifting device that can be temporarily turned off Their theory was, take two magnets (7x7x1.5mm in this case) place them between two iron plates with opposing poles and there should not be any field lines leaving the iron. Take away one of the...
  50. W

    Finding Magnetic Field for Bending Magnet - Help

    Hey everyone. I'm new here, but I figured I would jump right in. First of all, if this forum is anything like the forum I regularly participate in, then if this thread is in the wrong section, go ahead and move it to where it belongs, mods! I am a young (very young) researcher at FermiLab...
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