Magnet Definition and 99 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.

View More On
  1. 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...
  2. Woomir

    I Magnetic Levitation Issues

    [Mentor Note -- Two similar thread starts merged into one] Hey all, I have been working on this project for a while now, which features suspending an object midair through the use of magnetic levitation principles. Cool right? And so I have been researching and trying, even finding ground...
  3. T

    How distance affects the impact of magnet collision

    Hi, I'm studying how distance affects the impact of magnet collision. Would like to have some idea before conducting experiment. Imagine 1. holding a magnet at different distance near a fixed metal 2. release the magnet; the magnet attract and collide to the fixed metal Will the distance affect...
  4. 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...
  5. Steven Ellet

    Circular magnetic field?

    If you take a horseshoe magnet and fuse the north and South Poles together (without destroying the magnetic field) would you have a “pole-less” magnet? And if so, what special properties would it have(other than other magnets)?
  6. Gonzalo Lopez

    Motion Equation for a magnet on a spring

    Apart from the trivial elements of the motion equation (m z'' = -kz -mg), I am required to find the force produced by the Eddy currents induced by the moving magnet. To do so, I calculated the magnetic flux through the hole plate: For a magnet: Bz=μo m 4π. 2z^2−r^2/(z^2+r^2)^5/2 so Φ = a→ +∞...
  7. danielhaish

    Does it take long for magnets to respond to each other, and is it dependent on their separation?

    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...
  8. Luke2642

    Force & energy in cutting and stretching magnetic field lines?

    I have an ordinary switchable magnet for holding tools to a lathe. It's like a magnetic force gearbox, but I can't quite understand the force multiplication. When placed on a steel surface the switch force is approximately ~5N on both finger and thumb at 1.5cm radius acting over a 3cm arc...
  9. 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...
  10. Christoffer B

    Imperfections in magnet pole pieces

    Hi all, I'm fairly new here. I'm currently designing an as-homogene-as-possible permanent magnet for low-field NMR and similar experiments. I'm on a fairly tight budget, and having finally found pole pieces for my magnets, I got them even though they have a small saw cut in the edge. approx. 5...
  11. M

    Electromagnet that can generate 100 lbs at small size

    I wondering if it is possible to create an electromagnet that has a diameter of 0.5 cm that can generate 75 - 100 lbs of pull force. I took physics in college so I have a basic understanding of how magnets work, but I don't have any practical knowledge. I don't know what is feasible. I found...
  12. Z

    If a magnet could switch, could it attract and repel?

    Hello the first image with the letters going ABCD is picture #1 and then BACD is picture #2 for references. Tools: - Normal magnet. Nothing special about them. - And we will say they have some type of system where they do not move sideways. Only up and down and have a difference of 5 cm when...
  13. Z

    Small size Motor to generate this torque

    Good day everyone. I have two magnets where if I rotate them 20° they disconnect. It has a 0.4 N* m force of torque. I want to make them move with a motor. However I need it as little as possible. So after doing research I found tiny motors that are around 4000 RPM. It doesn't mention the HP...
  14. M

    Repulsion of the Earth's Magnetic Field

    I have a question why a magnet's magnetic field or a coil's magnetic field will not oppose the Earth's magnetic field? Is it because the Earth's field is not strong enough or the magnet/coil doesn't cover enough square area? What formula's would I use to figure out what strength or area I...
  15. P

    Magnetism Question

    My 7 year old child asked me today about magnetism. His question was "Does the magnet pull in the paper clip, or does the paper clip pull the magnet" . He then said to me "If i tie a rope to a tree and pull on the rope with enough force I will be dragged to the tree, so how do you know which...
  16. L

    I What causes magnetism at the atomic level?

    Lets assume we have a 1 foot square bar of Iron. I realize that unpaired valence shell electrons in an atom of a substance like Iron, all with the same electron spin---either +1/2 or -1/2---are consistent within the same atom, as indicated from the aufbau principle and experiments. So for an...
  17. S

    Creating any shape of a magnetic field?

    I was wondering if it was possible to create any shape of magnetic field. If yes, what would it take to do so?
  18. T

    In layman's terms , how strong is a 3 Tesla Magnet?

    I saw a post where someone was granted access to a 1.5 Tesla MRI. After some research I discovered a 3 Tesla MRI. How strong is this magnet?
  19. Happyholland

    Suspend a magnet on a pendulum above a repelling magnet

    Hi, I was pondering a question after seeing a video about chaotic magnetic pendulums. If you were to suspend a magnet on a pendulum above a repelling magnet, would it stop moving or would you get perpetual motion? My guess is it would stop moving but I can't think of how. Gravity would try to...
  20. S

    Electromagnetism homework check

    Hello. I have an assignment to submit and I really want to get full marks/know where I went wrong If anyone has a tiny bit of free time would you mind please checking my homework? Even if you just check 1 page I will be so grateful. Thanks again
  21. Dustin

    B 4 Questions About Lenz's Law Experiment

    Hello, I have four questions. As it stands now, I don't have the necessary materials to test this myself, which is how I'd prefer to learn the answer. I still plan on doing this experiment for fun once I can acquire the necessary components. This deals with Lenz's Law. My goal is to maximize...
  22. Suyash Singh

    Force on conductor in magnetic field

    Homework Statement Homework Equations Emf=B l V V is (velocity) F=QVB The Attempt at a Solution Emf=BLV Work=QBLV Force=BLV how come V=Q/m. its not possible or is it?
  23. A

    Calculating flux with a magnet and a coil

    Homework Statement [/B] Hey, I'm having some difficulties with my physics project and I hoped someone could help me out. We have to calculate the magnetic field, but first we need to know the flux. This is the setup we got: We have to let a magnet fall through a PVC tube. The tube has a coil...
  24. HastiM

    Is it possible to create a magnetic field which can be seen?

    Hello, I am wondering if one can create a magnetic field which can be seen by a human eye? I have learned that light is nothing else but electromagnetic field with a wavelength between 400-800 nm. Colours correspond to different wavelength within the above spectrum. So isn't it theoretically...
  25. C

    How to test toroidal permanent magnet with inside field

    As the permanent magnet is magnetized by donut shape coil, thus field B = 0 outside. How can I know if seller screwed me or not?
  26. VSayantan

    Speed of a Magnet Falling through a Conducting Wire

    Homework Statement A small but very powerful bar magnet falls from rest under gravity through the center of a horizontal ring of conducting wire, as shown in the figure below (on the left). The speed-versus-time graph, in arbitrary units, of the magnet will correspond most closely to which of...
  27. Marc Samarra

    Need references for magnetic force vs distance/angle topic

    Hi, i'm finishing my final degree project, it's about a new type of pallet conveyor dragged by magnets. I know for a fact that magentic force is inversely proportional to the distance squared, and I've designed and built my prototype with that in mind. Now I'm writing my final report and i need...
  28. Fibonacci Vonacci

    Magnetic Field of an AA Battery 'Immersed' in a Conductor

    If an AA battery were placed in some kind of ideal conducting 'ether': 1) Would current flow, and if so, what would the flow of electrons look like? 2) How would the magnetic field look? (I imagine that if there was an electric current flowing, that the magnetic field would look a little like...
  29. Sveral

    Cutting magnets

    Hello, could someone explain to me, how I should cut a FeBa magnet, if it has one pole facing upward and the other downward so that the bloch wall would be across the entire length of the magnet. The dimensions of the magnet at hand are 152 x 102 x 52 mm. The bloch wall runs across the entire...
  30. U

    How rubbing a needle on a magnet affects its polarity

    Homework Statement It is known that when rubbing a needle on a magnet, the needle will become magnetized. If you rub the needle on the north side of the magnet, will it point differently than if you rubbed it on the south side of the magnet? Does it matter what direction you rub the needle...
  31. 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.
  32. I

    Obtaining position in a dipole field

    Hi all, Consider one has a magnetic dipole, the field given by: \begin{equation} \vec{B} = \frac{\mu_0}{4\pi}\left(\frac{3(\vec{m}\cdot\vec{r})\vec{r}}{r^5}-\frac{\vec{m}}{r^3}\right) \end{equation} where we can take $$\vec{m} = m\hat{y}$$. Let us say we have the a magnet vector which is...
  33. S

    Moving charges and magnetism

    Homework Statement current in wire is in east to west direction.direction of magneetic field below the line Homework Equations right hand thumb rule The Attempt at a Solution i used the right hand thumb rule to find the direction of magnetic field but the magnetic field comes out in in the...
  34. S

    I Where does the formula I = -e/T comes from?

    Yeah, where does it comes from?
  35. Y

    MOSFET or Rheostat or Potentiometer pros and cons?

    Preface: I'm a chemical engineering undergraduate student but as small-time and noob electrical engineering hobbyist. I really only have minimal experience in circuitry and the like. I want to build a series of electromagnets with a variable their strength in order to levitate an opposing...
  36. A

    How can the neutral outer core generate a magnetic field?

    Even if the outer core is convecting and conductive it is still charge neutral, so how can a Magnetic field be generated? Maxwells Equation say there needs to be net charge moving for a Magnetic field to be generated.
  37. C

    Need help doing force calculations with magnetism (between magnets)

    I am trying to calculate the forces (in Newtons) between a permanent magnet, and an electromagnet. All I can find is interactions between permanent magnets, electromagnets, but never both and it is getting really confusing for me to do the calculations. So basically, if I have a permanent...
  38. C

    Solutions of wave equation but not Maxwell equations

    Maxwell equation in absence of charges and currents are $$\nabla \cdot \bf{E} = 0 \\ \nabla\cdot B=0 \\ \nabla \times E=-\frac{\partial B}{\partial t} \\\nabla \times B=\mu \epsilon \frac{\partial E}{\partial t}$$ Wave equation is $$\nabla ^2 \bf{E}=\mu \epsilon \frac{\partial^2...
  39. J

    Can a magnet have more push force than it weighs?

    Simple question. Can a magnet have more push force than the magnet itself weighs. Example: A magnet weighing 2kg having a push force equal to 3kg.
  40. A

    How do you calculate the force between two magnetic dipoles?

    I've seen a couple of equations on Wikipedia and other sites and all of them are different. I need an equation as I want to specifically calculate the force between a magnet and a steel ball. The equations I've seen is this one here...
  41. G

    Magnetism - stability of a ring with a sphere inside it?

    Hey, is it possible to have a cylindrical ring (made of permanent magnet) and a magnetic sphere sitting inside it and staying in one place without touching the inner sides of the ring and not falling through? The object doesn't necessarily have to be a sphere. If it would work with any other...
  42. D

    Interaction between a neutral atom and an external magnetic field

    Lets suppose that I have a magnetic dipole moment at (0,0,0) pointing to the Z axis, and in the position (X,Y,Z) in the space, I have a Hydrogen atom, I would like to know the exact interaction between the magnetic field created by the magnetic dipole moment in (0,0,0) and the magnetic fields of...
  43. Qwerty42

    I Forces applied to a leaning levitating bicycle

    Hi! So I'm building an electromagnetic bicycle where the frame is levitating over the wheels, thus reducing the rolling friction to almost zero by removing the bearings. Magnets have also been placed alongside the wheels to provide side to side stability. Black is the frame, red are the magnets...
  44. Undacuva

    Pipe or coil in generators

    Hi, I understand you can induce an electrical current by passing a magnet through a copper pipe. If so, why do generators (and motors for that matter) use coils in stead? Do coils allow a stronger current or greater efficiency? Where can I go to find out the most energy-efficient design for a...
  45. r_prieto5

    Solenoid force calculation

    Hello everyone, So for a personal project I want to calculate the force necessary for a solenoid (electromagnetic coil) to keep a permanent magnet triangle locked diagonally up and down at the same time so that it does not move in any direction. I need to know the values for coil thickness...
  46. cluelessGUY

    Magnet clamp repelling in coil

    I have a practical question. I want to make a rubber (silicone) hose/plug that is pinched closed by two magnets ( very strong magnets such as ones from a hard drive the Neodymium kind). I want to place then into a coil and when I want the liquid to flow, I want to turn on the coil and have the...
  47. T

    Metal: no attraction to magnet and block magnetic fields?

    Hi, Can anyone help me in finding out a Diamagnetic or Paramagnetism or Ferromagnetism or any other metal which has following capabilities: 1- Should not be attractive towards magnet. 2- Should not allow magnetic fields to pass through inside. Thanks! THG
  48. G

    Ballistic Lenz's Law

    If a magnet was going fast enough as it approached/entered a copper tube, could the current induced in the tube via Lenz's Law be high enough to melt or even vaporize the tube?
  49. E

    B Does a moving bar magnet create charges?

    So I understand that a charged particle moving relative to me has a magnetic field, and does not have one if its stationary relative to me... So is it true that a magnet moving relative to me has a charge? Say I took a bar magnet and threw it away from me way out in space, would it acquire a...
  50. Shahsquatch

    Magnet Fundamentals and Iron Powder

    I am creating a product that incorporates magnetic sensing of magnetic nanoparticles. However due to their cost, I have decided to search for other avenues of testing. My question is about whether Iron Powder will retain a magnetic field once magnetized. I basically will place some iron powder...