What is Magnetism: Definition and 970 Discussions

Magnetism is a class of physical attributes that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomenon of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron, cobalt and nickel and their alloys. The rare-earth metals neodymium and samarium are less common examples. The prefix ferro- refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4.
All substances exhibit some type of magnetism. Magnetic materials are classified according to their bulk susceptibility. Ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, but there are actually several types of magnetism. Paramagnetic substances, such as aluminum and oxygen, are weakly attracted to an applied magnetic field; diamagnetic substances, such as copper and carbon, are weakly repelled; while antiferromagnetic materials, such as chromium and spin glasses, have a more complex relationship with a magnetic field. The force of a magnet on paramagnetic, diamagnetic, and antiferromagnetic materials is usually too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic.
The magnetic state (or magnetic phase) of a material depends on temperature, pressure, and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change.
The strength of a magnetic field almost always decreases with distance, though the exact mathematical relationship between strength and distance varies. Different configurations of magnetic moments and electric currents can result in complicated magnetic fields.
Only magnetic dipoles have been observed, although some theories predict the existence of magnetic monopoles.

View More On Wikipedia.org
Recent contents Top users
  1. K

    Magnetism -- Clarification about North and South magnetic poles

    When I look at images of the pattern of iron filings around a magnet I cannot see any difference between the Pattern at the 'North' and 'South' poles. The present model also says that the field 'flows' from North to South but if this were the case it would not be necessary to move a magnet near...
  2. P

    Magnetism used as a repulsive force

    Is it possible to create such a strong repulsive force using 2 magnets that it can essentially keep these 2 objects from touching each other? Basically if there are 2 objects coming at very high speeds if both of these objects had a magnet on them that can create such a strong repulsive force...
  3. P

    Why Might a Rotating Ring in a B-field Ignore Certain Torques?

    Summary:: Please see the attached photo. I have obtained the correct answer, and my solution agrees with the official solution. However, I have some questions about why the solution is correct. (One may have to draw out some diagrams for this problem, it was quite hard to visualise for me.)...
  4. P

    Problem on induced electric field, electrodynamics

    The problem is shown above, the hint to solve the problem is below. See the hint if it is difficult for you to imagine what is going on. I am assuming the diagram in the hint shows what's happening when the mass is falling at terminal velocity. I have quite a few questions. 1. How do the wheels...
  5. P

    Does a charged insulating ring turn if a B-field is switched on?

    The physics behind this problem is that an electric field is induced (by Faraday's Law), when the B field is switched on. Charges on the ring now experience a force as given by dF = E dq. Apparently, because of this, the ring starts rotating. I understand that charges in an insulating material...
  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. Mr_Allod

    Magnetic Field, Field Intensity and Magnetisation

    Hello there, I've worked through this problem and I would just like to check whether I've understood it correctly. I found ##\vec H##, ##\vec B## and ##\vec M## using Ampere's Law and the above relations as I would for any thin current carrying wire and these were my answers: $$\vec H = \frac I...
  8. P

    Interactions Between 2 Dipoles

    Draw graphs showing how interaction energy depends upon the relative orientation of two dipoles if (i) p1 is parallel to r, (ii) p1 is perpendicular to r. I've done the first part and found the interaction energy as UInt = 1/(4*pi*epsilon0*r^3)*[p1.p2-3(p1.r^)(p2.r^)] which I know is correct...
  9. S

    Upright Storage of Tiny Screws Using Magnetism

    It's a long story, but I'm in the process of taking apart 100s of laptops involving 1000s of laptop screws. I'm trying to come up with ways to take the screw off the drill bit, keep it upright, and then weaken the bond enough so the drill bit will pick up again- to put the screw back. Right...
  10. D

    Magnetism: Properties, Effects & Uses - 65 Chars

    Homework Statement:: Is magnetism a property of materials? Can magnetism be increased, decreased or even completely removed from a material? Relevant Equations:: Nil Dear seniors, This isn't my homework but this simple word "magnetism" has been bothering me for some time. I know that a...
  11. 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.
  12. T

    Magnetism Question about the MMF and a Steel Ring

    Summary:: This question is in relation to finding the mmf of a cast steel ring. Unfortunately I do not know how to post a picture of the page showing the graph. [Mentor Note -- Thread moved from the technical forums so no Homework Template is shown] A cast steel ring has a cross sectional...
  13. V

    Magnetism lab involving a nail and an Allen wrench

    So basically what I had to do was: 1. take a Allen wrench and let it come in contact with an iron nail. Nothing happened here. None of the objects are magnetic. 2. take the Allen wrench and let it touch the North end of a magnet. Then let the wrench come in Contact with the iron nail. Here the...
  14. Elder1994

    Magnetic field due to the current flowing in a bent wire

    Hello, in this problem I'm supposed to calculate de magnetic field due to a bent wire at any point of the x-axis after the bending of the wires. It is obvious that the part of the wire that is parallel to the x-axis makes no contribution to the field so we can focus on the other part of the...
  15. A

    [Magnetism] Determine the direction of the force experienced by a (+)C

    Given: q = 1.6*10^-19 C B = 0.3 T north v = 3*10^6 m/s north-west θ = 37 (degrees) Solution Attempt: a) F = Bqvsinθ = (0.3)(1.6*10^-19)(3*10^6)(sin(37)) = 8.7*10^-14 N b) Via right hand rule, F is into the page c) a = F/m = 8.7*10^-14/1.6 × 10^−27 = 5.4*10^13 m/s^2 When I checked my answers...
  16. A

    Confusing the Two Sections: How Does Magnetism Work?

    I noticed that I posted this question on the wrong section previously by accident and I don't know how to delete it... Sorry for confusing the two sections====== Given: - A sticks to B - B doesn't stick to C My solution: As A sticks to B, one must be a magnet and the other iron. As B doesn't...
  17. E

    Potentially silly question re magnetism....

    The unit for flux density (a derived SI unit) is Tesla, this can be expressed as T = N*s/C*m. Ie a particle with charge of 1 coulomb, traveling at 1m/s perpendicular to a magnetic field of 1Tesla experiences a force of 1N. So my question, and this is more for my understanding since I'm not...
  18. J

    Conventional current, magnetic fields and magnetic poles of different diagrams

    I need to do question 1. I understand the right hand rules but am lost on what to do here.
  19. astrocytosis

    Magnetic field of a rotating cylinder with permanent polarization

    I am struggling to get my work to match the posted solutions to this problem. I understand part (a) but can’t get the integral to work out for (b). I know I have to use Biot-Savart and add up the components from the the surface and volume currents. The cylinder is very long, so I need to make a...
  20. fisher garry

    Magnetic field inside a solenoid

    I have a problem with the derivation above I don't get how Can someone derive this and illustrate this visually for example by using Figure 2 or using another drawing?
  21. patrykh18

    Magnetic field outside a solenoid

    In his book on electrodynamics, Griffith talks about the magnetic field outside a solenoid. Firstly instead of dealing with a typical solenoid with closely wound loops, he instead works with a cylinder with a surface current that has no z-component. To get the angular component of the B-field...
  22. harsh22902

    Flux & Physics: Explaining the Constancy of Flux

    This is an excerpt from a high school physics textbook. I don't understand the possible reason behind this statement. If we change something in the circuit say for example add a resistor , the current and hence the flux should change. Then why/how is this statement true?
  23. rayjbryant

    I Exploring Lenz's Law: Magnetic Flux and Induced Currents

    I've attached an illustration of my set up.
  24. H

    Magnetism vs Altitude: Magnetic Pull & Gravity

    Magnetism as an attractive force can overcome gravity and lift things. I'm suggesting that a horseshoe magnet will overcome gravity and lift things off of the ground. Is there a reduction of magnetic pull with altitude?
  25. Z

    Eigenstates of a free electron in a uniform magnetic field

    I started with the first of the relevant equations, replacing the p with the operator -iħ∇ and expanding the squared term to yield: H = (-ħ^2 / 2m)∇^2 + (iqħ/m)A·∇ + (q^2 / 2m)A^2 + qV But since A = (1/2)B x r (iqħ/m)A·∇ = (iqħ / 2m)(r x ∇)·B = -(q / 2m)L·B = -(qB_0 / 2m)L_z and A^2 =...
  26. Physics lover

    Motion of a particle in a uniform magnetic field

    All i could think is that the z component of velocity will remain unchnged as there is no force in that direction.And for the x and y component can we imagine the helical motion as a superposition of a circle and a straight line.So for x and y component can we solve for a particle moving in a...
  27. W

    Relation between magnetism and material creep

    Hello, I am a civil engineer and have been working on concrete creep phenomenon for several years now. After reviewing a large amount of literature on related topics throughout this time, some interesting observations have emerged, and they have formed the idea that the material creep mechanism...
  28. H

    What exactly is magnetism, anyway?

    After carefully reading textbooks, research papers and a lot of forums, I find myself more confused than ever regarding the composition of magnetic fields. So please let me ask some (hopefully) very simple questions: (1) Do we or do we not know exactly how magnetic fields arise and dissipate...
  29. TheBigDig

    Force on a magnet in a magnetic field

    So I'm kinda stumped. I'm assuming that since ##\vec{m}||\vec{B}##, the x and y components of both are zero. But I'm unsure how to take this further.
  30. GiacomoPaini

    I forgot the name of a theory in Magnetism

    Can you help me I don't remember a theory The name was something like Theory ok kamp (Kemp? ) Something like this This theory is about magnetism, more precisely about how two sources shield and influence the field) Do you know the name thank Jacky Thank you
  31. C

    What are some common misunderstandings about magnetism and relativity?

    Hello, there are a couple things about magnetism that I do not understand. 1. Why didn't we define the magnetic field to be in the directions of the force? This isn't really a technical question, I am just more curious about why it is this way. The way I was thinking of it, the math seems to...
  32. B

    A question about magnetism that causes a wheel-loop to rotate

    This question is from 1977 AP Physics C so I suppose it would be clear enough, but I am confused about question c. Question a is easy (it rotates counterclockwise), question b too (Στ=6*rxF=6*r x (I*i x B)=0.06). Question C is where I am stuck. The diagram provided with the question looks like...
  33. B

    Biot Savart Law with Different Magnetic Permeabilities

    I would like to make a program that produces a 2D heat map showing the magnitude of the magnetic field produced by a finite length solenoid. The heat map would show the field strength along the radial and axial directions of the solenoid. I plan to divide the conductor into "infinitessimally"...
  34. Zack K

    I Do two perpendicular wires exert a force on each other?

    I have a question for my E&M assignment (I'm not putting it in the homework thread since I just need more of a concept check) that involves a straight wire with current through it. If you have a wire with a current through it, and you have a rectangular wire also with current, to the right of...
  35. ChinoSupay

    Exploring the Cosmos: A Chilean Astrophysicist's Journey in Magnetic Research

    I am a chilean astrophysicist that works currently in magnetic issues in the Earth, planets, star and cosmos in general. I'm also interested in graphic desing, art-science relationship and dance. Thank you!
  36. Hawkingo

    What are some good books on electricity and Magnetism

    Can someone please suggest some good books on electricity and Magnetism for graduation in physics? Thanks for helping:smile:
  37. S

    I How does magnetism work in QM?

    Electrons' spin state is responsible for magnetism inside a magnet. Two magnets interact at a distance, but what about the space between and around the two magnetic objects? In CM there are field lines and vector fields, but what is actually happening at the QM level?
  38. P

    Magnetism: Explaining the Attraction to a 7-Year-Old

    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...
  39. Celso

    Induced EMF — generator coil area calculation

    Homework Statement What is the necessary area for a generator that produces an emf of ##\mathcal{E} = 150V## when it spins at a ratio of 60 revolutions per second, in a magnetic field of ##B = 0.5 T##? Homework Equations ##\oint_{c} E \cdot dl = \mathcal{E} = -\frac{d}{dt}\iint_{s} B \cdot dS...
  40. DeathbyGreen

    I Database for magnetism and properties

    Hi, I'm trying to find a database in which I could enter a chemical formula and then locate a table of physical properties of that compound (or references). For example, whether the material exhibits magnetism, superconductivity, it's crystal structure, curie temperatures, conductivity, or...
  41. cookiemnstr510510

    Forces of a straight wire on a semi-circular wire loop (Magnetism)

    Homework Statement An ideal, infinitely long straight wire carries a current I1 and is partially surrounded by a loop of current as shown below (image attached). The loop has length L, parallel to the infinitely long wire. The loop carries current I2. A) Calculate the magnitude and direction of...
  42. DLeuPel

    Can Mu metals redirect a magnetic field?

    I am trying to find a way to decrease the force between two magnets by putting a physical barrier in the middle of them. I’ve reasearched and found that Mu metals redirect the flux of the magnetic fields so those two magnets shouldn’t have any noticeable attraction between them. Of course...
  43. P

    Are these instances of identical magnetic fields?

    Are both magnetic fields emanated from an electromagnet fed with a current spike from a charge capacitor and a rotating static magnetic field from permanent magnets instances of time varying fields? The permanent magnet would be attached to perhaps some rotating disc thus passing over a target...
  44. A

    I What was the value of the permeability constant in 1865?

    What is the value of the permeability constant in 1865, the time when Maxwell's theory was first published? What was the experimental method used to determine the constant. Who did the experiment.
  45. Celso

    Nullifying Lorentz Force on Proton Moving in Parallel Direction

    Homework Statement A proton moves with a speed ##v = 3 \cdot 10^5 \frac{m}{s}## in the parallel direction to ##i+k##. A magnetic field of ##1T##, in the ##i+j+k## acts over it. Which electric field must we apply in this region so that the Lorentz force over the proton is null? Homework...
  46. 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...
  47. Silentwhale

    Electricity and magnetism (Gauss' law)

    Homework Statement Given two things spherical shells radii r1 and r2 with r2 > r1. The inner she'll is charged uniformly with a total charge Q1, while the outer shell with Q2. A) use gauss law to computer the electric field everywhere B) Use any method to calculate the potential everywhere...
  48. Silentwhale

    Electricity and magnetism: Electric Field for Two Long Charged Lines

    Homework Statement Given two very long lines each is charged with linear density +lambda Coulombs/meter. The two lines are separated by a distance of d metres. A) show the electric field E, at any point along one of the lines due to the other line is E = lambda/(2 (pi)(epsolon o)(d)) (Note...
  49. coolul007

    Magnetism and atomic structure

    Does atomic structure require a magnetic force? I understand that in the world of people it is most appreciated, however, it doesn't seem to have a purpose in the atomic structure.
  50. Mr C Odd

    Time dilation in a magnetic field

    Hi all. I was wondering if time is dilated whilst traveling in a stable magnetic field that is generated by the object travelling, and if so, does this vary if you reduce or intensify the magnetic field? Also, what happens if the object is generating two opposing magnetic fields, would...
Back
Top