What is Magnet field: Definition and 20 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 Wikipedia.org
  1. D

    Deduction about Magnetic Poles surrounding a Conductor

    As shown in the diagram, a copper conductor is placed over two stretched copper wires whose ends are connected to a D.C. supply. What should be the magnetic poles at points A and B lying on either side of the conductor to experience the force in the upward direction?-------------------- My...
  2. Rayan

    What is the energy difference between the peaks in the Zeeman effect?

    But I don't really know how I am supposed to find the energy difference from the graph, how can I know which peaks to use?
  3. doomer

    I Geometry of Magnetic field lines as they approach a magnet pole?

    Magnetic field lines are loops, so at the surface of a magnet (axially magnetized) cylinder) pole they look like this? there is a dead zone at the center where there is no lines/magnetic field present? or perhaps they look more like this? lines converge in the middle to a single line or point...
  4. N

    I Resulting magnetic field due to the passage of an AC current

    Hello, Assuming that we have a single-phase electrical transmission line (short distance (< 50 km), stranded, non-isolated, made of aluminum conductor steel reinforced), I would like to know the resulting magnetic field (shape, structure, absolute value, and all other possible details) when...
  5. Manuel12

    Magnets with Halbach array in an AC generator

    As a project, I am demonstrating electromagnetic induction by making an AC generator. The magnets I currently have access to are very strong neodymimium countersunk magnets, but I noticed that they utilise a Halbach array. I am aware that this means the magnet has alternating N-S poles spaced...
  6. I

    Directing magnetic field lines by using diamagnetic material

    I want to improve the magnetic field strength at the surface of a magnet configuration by utilizing diamagnetic materials to guide the magnetic field lines. I have not the proper equipment to measure the effect myself but would this work? This is the initial configuration with four magnets side...
  7. S

    I Magnetic fields are exceptions to the second law of thermodynamics?

    Einstein famously said “{Thermodynamics} is the only physical theory of universal content, which I am convinced, that within the framework of applicability of its basic concepts will never be overthrown.” I don't think any of us want to argue with Einstein, but it's worth noting the "within the...
  8. 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...
  9. S

    Halbach-Array Simulation FEMM

    Hello everone, I have recently come across the need of a strong constant magnetic field while being limited in space. The field needs to be unidirectional and up until now was generated by two magnets (12x12x12mm N48). Then I came across Halbach arrays and their potentially stronger magnetic...
  10. gumthakka

    Current and stationary charges

    I've learned that moving charges produce magnetic fields which in turn affect other charges in motion. After seeing explanations that point to special relativity, I am kind of confused. Can **ALL** magnetic fields be accounted as some kind of electric field from a particular reference frame...
  11. A

    Understanding a step in a Biot-Savart law problem

    I can't understand intuitively why the authors of the book expressed the cross product between the vectors dl and r (unit vector) as: dl sin(pi/2 - theta); isn't it supposed to be expressed as: dl sin(theta)?? So why did the authors put that pi/2 into the argument of sin function, that's my...
  12. D

    How to find the magnetic field and magnetic force due to a solenoid loop

    I'm not so sure how to begin with this problem. I was thinking of usign superposition. I think that the field on the conductor due to the parallel segments of the coil is zero, since Ampere's Law tells us that the field outside the solenoid is zero, right? For the perpendicular segments, I used...
  13. Nonametheone

    Mini magnetosphere within Earth's Magnetosphere

    Summary: Can such magnetosphere exist on Earth? The moon has mini magnetospheres produced from its crust shown below. Can Earth have similar magnetic properties in its crust like the surface on the Moon to create a mini-magnetosphere? Are ther places on Earth where a mini magnetosphere exist...
  14. W

    The direction of magnet field

    for a infinite length length of current, only consider a part of it, is the direction of magnet field of a ring on the mid vertical plane the same magnitude and along the tangential direction? and for a closed surface , if the flux is 0?
  15. jfizzix

    Can you cancel part of a permanent magnet field by spinning?

    It's a random thought I had. Let's say you have a single perfect permanent magnet. There is just one magnetic domain, and the magnet is cut so that its magnetic moment is along a single crystal axis. For example, we can imagine a cube shaped magnet, with the magnetic moment pointing straight...
  16. D

    Use moon as generator w earths magnet field

    A moving magnetic field will produce current in a wire. The Earth's magnet field goes beyond the moon. Does that mean bases on the moon could somehow get free energy from a coil setup as it's effectively perpetually moving through Earth's magnetic field?
  17. Z

    Magnet Field of a Solenoid: Understanding the Derivation Step by Step

    Homework Statement Attached file shows the problem statement. The Attempt at a Solution I can do this problem easily. Problem is that there's just one step in my book's derivation that I don't understand. It sets ρ equal to the hypotenuse in the triangle and then says that: dl = ρ/sinθ...
  18. G

    About magnet field in solid oxydes fuel cells

    Hello! I don't understand one easy moment in high temp solid oxydes fuel cells (SOFC): 1. Oxygen ions are moving always via solid electrolite ZrO2? SOFC without load and SOFC in short circuit modes. (High temp is default mean) 2. Electrolises process need electric energy and external...
  19. R

    Neodymium ball magnet field alignment

    If a magnetised neodymium ball has a definite north and south point, could you slice the ball in two, and weld 2 "north" halves together, to create an entirely north ball? If this is impossible, how about designing a ball made in, say, a 3D printer, then embed it with small magnetised neodymium...
  20. A

    Link between magnet field from a wire and inside a capactior

    The magnetic field Bw is measured at a distance b from the centre of a long thin wire. The magnetic field Bc is also measure inside the capacitor plates at a distance b from the axis of the capacitor, where b is less than the radius "a" of the plates. using Maxwell's equations, show that...