What is Magnetic: Definition and 1000 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
  1. G

    A Maxwell says that Div B = 0

    So if Maxwell's Equations state that Div B = 0 which is a statement that there are no magnetic monopoles why do some folks claim that Cosmic Inflation "dilutes" magnetic monopoles?
  2. F

    Monitor's magnetic field setting off handheld CO detector

    Hi, I have a small handheld CO detector (https://www.amazon.com/gp/product/B08SQPKTGN/?tag=pfamazon01-20), and I've noticed that leaving it on my desk near my monitor will invariably trigger the alarm. There are magnets that are housed at the base of the monitor (an old mac Thunderbolt display)...
  3. A

    Magnetic Field Due To Wire Of Semi-Circular Cross Section

    I proceeded as follows Current in sector ##d\theta=## is: $$dI=\int_{x=0}^{x=R}{\frac{I}{\pi R^2/2}\times\frac{d\theta}{2\pi}\times 2\pi x dx}$$ Field due to sector ##d\theta## is therefore $$dB=\int^{x=R}_{x=0}{\frac{\mu_○}{2\pi x}\times\frac{I}{\pi R^2/2}\times\frac{d\theta}{2\pi}\times 2\pi x...
  4. K

    Calculation of the magnetic field of four quarter circles

    The diagram is something like this, and I want to calculate the magnetic field at the center using the Biot-Savart law. In this case, do the magnetic fields formed by the quarter circles pairwise alternate with each other?
  5. tanmays1

    Does levitation distance increase as Fg increase???

    I'm trying to conduct an experiment where I calculate the magnetic field strength of a magnet, by comparing the levitation distances between two magnets. My experiment involves using different masses to anchor down magnetic repulsion between 2 magnets. Fg = Fm. The formula I am using for this...
  6. fmorgan2

    B Changing magnetic polarity of an electromagnet

    I would like to change the polarity of an electromagnet. I have reversed the wires attached to a 9 volt battery that wound about a bar magnet but this did not seem to make the north pole become the south pole. Thanks for your assistance, Frank
  7. S

    I Shielded magnetic loop probe / antennas

    From a purely physics point of view, what would be the performance tradeoffs between the following types of shielded H-field pickups or antennas? Sources: https://owenduffy.net/blog/?p=18180 https://emcesd.com/tt120100.htm (A) (B)...
  8. S

    Magnetic and Ultra-Sonic Interests

    I'm an entrepreneur with an interest in Magnetics and Ultra - Sonics. I have a strong belief that there are many more applications in which both could be utilised to minimise the use of various energy forms. I am here simply to learn and understand and ultimately to connect with members who...
  9. Szecska8

    I Stored magnetic energy of solenoid

    Can someone explain to me what the second integral represents and what is A?
  10. harryharns

    C/C++ Perform RK4 between 2 Clusters in Magnetic Field

    I have a simulated data of charged particles in a magnetic field. I have selected clusters, each cluster contains a set of points(x,z) and I want to perform RK4 between the first and second clusters and fill the positions in a histogram. I have selected the clusters with the initial...
  11. ergospherical

    I Average magnetic moment of atom in magnetic field ##B##

    from the partition function - am trying to show that ##\langle \mu \rangle = \beta^{-1} (\partial \log Z / \partial B)## where ##Z## is the canonical partition function for one atom, i.e. ##Z = \sum_{m=-j}^{j} \mathrm{exp}(\mu_0 \beta B m)##, and ##\mu = \mu_0 m##. The average...
  12. D

    B Magnetic field and generator power output

    Hi, I am confused about whether decreasing the magnetic field used for a generator could increase the generator's power output. I used four equations: 1. Torque = Force x radius 2. Torque = NIAB (N = number of turns, I = current, A = area of armature, B = magnetic field). 3. emf =...
  13. rogdal

    Classical magnetic dipole-dipole interaction in iron

    I'm having a bit of trouble with this exercise because, even if I understand the physics of the dipole-dipole interaction in an ideal classical system, I don't get to know how to approach this problem. I've got a few doubts about how this system would work. First of all, what would be the...
  14. G

    B Should I use True North or Magnetic North to align my sundial?

    I'm not sure I asked the correct question. I am trying to learn when our sun is at solar 12 noon on my yard, does the sun light travel a perfect path across earth, 50% before solar 12 noon and 50% after solar 12 noon. I built a large sun dial in my yard 3 ft tall 6 ft long. I used a compass...
  15. milkism

    A diamagnetic sphere in a uniform magnetic field

    Problem: Solution part a) where formula 6.14 is just M x n. We need to do part b without seperation of variables, I'm quite stuck. Will B just be the magnetic field inside a solenoid? How can I find the other fields.
  16. M

    Electron in a time variable magnetic field

    TL;DR Summary: Find acceleration of electron in dB/dt >0 Hello. Here is a problem that i'm not so sure about: Inside a solenoid there is a time-dipendent magnetic field B, so we have dB/dt = b (constant). We want to know the acceleration of an electron: a) placed in the center of the solenoid...
  17. B

    I How to depict a nuclear magnetic octupole

    Hello! I am not sure if this is the best place for this question, but I want to make a simple illustrative drawing (for a presentation given to people both with and without physics knowledge) of a nuclear magnetic octupole moment. For example for a magnetic dipole I can use a magnet as a...
  18. M

    Faraday's law and Magnetic Fields

    I am not really sure which direction i am moving in with this solution
  19. S

    Exploring Propulsion with Light & Magnetic Fields

    while browsing for new propulsion methods I found the following interesting: https://en.wikipedia.org/wiki/Radiation_pressure "Radiation pressure (also known as light pressure) is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the...
  20. S

    Magnetic field force between two perpendicular wires

    There are a couple of problems with the same setup. On plugging in the values and solving for the integral, I am not getting the expected values of the force. Is there something wrong in the solution attached?
  21. F

    Determining Radius from Magnetic Field of a Single-Wire Loop

    So I thought I knew how to do this problem but I've run into some issues that make the algebra feel impossible and I am beginning to feel like I'm taking the wrong approach, I ended up rewriting it in a doc because I was concerned maybe my handwriting was the cause of my error so the work is...
  22. Brian Tsai

    I A math confusion in deriving the curl of magnetic field from Biot-Savart

    I am recently reading "Introduction to Electrodynamics, Forth Edition, David J. Griffiths " and have a problem with the derive of the curl of a magnetic field from Biot-Savart law. The images of pages (p.232~p233) are in the following: The second term in 5.55(page 233) is 0. I had known...
  23. H

    Why a particle with spin=0 can't posses a magnetic dipole moment?

    Hi, I would like to know why a particle with spin=0 can't posses a magnetic dipole moment? Using Wigner-Eckart theorem for ##\langle j,1,m,0|j,m \rangle## I get ##\langle j'|| \vec{J}|| j \rangle = \hbar \sqrt{j(j+1)} \delta_{jj'}## It seems like the right hand side is the magnetic dipole...
  24. S

    B Magnetic Field & Particle Spin: Does It Matter?

    Does the magnetic field caused by moving particles depend on the particle spin value? Eg a stream of say protons spin 1/2 is creating a magnetic field. If the particles are (say) lithium nuclei spin 3/2 instead, does that create the same strength field ? (same conditions of course)
  25. milkism

    Magnetic- and Electric- field lines due to a moving magnetic monopole

    Question: My answer: What it looks like for an electric charge: Am I correct? If you want I can hand out my Latex on how I got to it, it will refer to the book Griffiths a lot.
  26. milkism

    Electric and magnetic fields of a moving charge

    Part a) My solution: Big R basically becomes r, and the electric and magnetic field lines are doubled because of superposition principle. Am I right?
  27. Grizzly_1

    B Confusing diagram of a rotating coil in a magnetic field

    Hello all, I am currently studying for a physics a-level qualification in the UK, I use the AQA specification and I am having trouble understanding this image representing a scenario I found in my textbook. The first image in the three part diagram shows this rotating coil and to me, it makes...
  28. B

    Flyback Converter Magnetic Flux Calculation

    Hi I am designing a flyback converter. The calculation (.jpg file) is based on Daniel W. Hart Power Electronics book. The transformer model consists only of an ideal transformer and its magnetizing inductance (or "primary inductance" in some textbooks). The datasheet of the transformer's core...
  29. K

    How can I troubleshoot and verify my calculations for magnetic force?

    I am getting a wrong answer for part b, however part a and c both are correct : a. 0 N b = -2.91E-3 N (WRONG) c. 1.4E-4 N
  30. J

    Best way to measure magnetic waves for electromagnetic induction

    Hi all, Looking to measure some magnetic waves being generated at an electric coil. Freq is between 0-20kHz and magnitude is pretty small <1T. Any have suggestions for the best tool to measure and log data of this magnetic waveform? Googling around, I found meters like this: [Possible spam...
  31. A

    B Magnetic field coil ferrous material for loudspeaker

    Hi everyone. there are materials called soft magnetic and they are halfway between a permanent magnet and a ferromagnetic material. I would like to try to make a field coil loudspeaker where the maximum amount of flux-density is very important but also the amount of current it takes to create...
  32. J

    Thin heartshaped wire - Calculate the magnetic field at the origin

    Hi, So I know I am to use Biot Savarts law dB= (my_0/4pi)* (I dl x (r-r')/|r-r'|^3 where r=0 because its in origo and r'=r'_c(r'_hat). This makes (r-r')= -r'_c(r'_hat) and |r-r'|^3= r_c^3. From previous questions, I have defined dl' as the infinitesimal displacement of r'(phi) when phi' is...
  33. D

    I Question on Hall Effect and magnetic force

    so with a Hall Voltage, you have positive current traveling upwards in a wire in the +y-direction and a magnetic field into the screen in the -z-direction. the right hand rule has positive charge deflecting to the left. now if you look at the drift velocity of electrons moving downward in the...
  34. O

    Motional EMF in the presence of a time-varying magnetic field

    My question arises from the following problem: We have a uniform magnetic field into the page, decreasing at a constant rate dB/dt< 0, causing the bar to move to the right. Find the velocity of the bar as a function of the time, and in terms of the known parameters: the resistor R and the...
  35. A

    Relationship between magnetic field lines and magnetic field

    As stated in the problem, I want to demonstrate mathematically that field line density is directly related to the magnitude of B. How would I be able to do this, other than simply using the flux equation and showing that for a higher flux in the same area, the magnetic field must be rise...
  36. S

    I Behaviour of Magnetic Fields Underwater

    I've been trying to pick up the fundamentals of electromagnetic theory and I reckon I'm doing alright, but I've run into a some questions about how magnetic fields behave in an anisotropic fluid medium like the ocean. There is an awful lot of conflicting information online. Ultimately, I'd like...
  37. kuruman

    Finding a Parametric Solution for Particle Trajectory in Magnetic Field

    This is a solution to a problem inspired by another thread. It is posted here to separate it from the multiple choice question which was the subject of that thread. A parametric solution for the trajectory can be found quite easily if the motion is modeled as a particle with charge ##q##...
  38. C

    Magnetic Field Due to a Curved Wire Segment

    For this problem, The solution is, However, why did they not use limits of integration for the integral in red? When I solved this, I used as limits of integration. I see that is not necessary since you get the same answer either way, but is there a deeper reason? Many thanks!
  39. C

    Magnetic Field Surrounding a Straight Conductor

    For this problem, Part of the solution is, However, would someone please tell me where they got the sine function circled in red from? Many thanks!
  40. davidj

    Magnetic and Electric Fields problem

    Would i assume that fg = fm (force gravity holding straight wire down is equal to the magnetic force) and isolate for I? Help if you're available please!
  41. J

    Calculating Area & Direction of Magnetic Field

    Hi, the problem statement is above. I have some questions about how to calculate the area and the direction of the magnetic field of this problem. As the magnetic flux, my professor have defined it as Phi= integral(B dS)=(Area)e_x B= (Area_triangle + (L^2/2) *(β + α(t)))*B e_z. How can one know...
  42. sal1854

    I Direction of motion of particles with total spin under magnetic field

    According to Chapter 8 of Griffiths' book Introduction to Electrodynamics, the magnetization force that acts on a magnetic dipole is $$F_M=\nabla (m \cdot B)$$, where ##m## is the magnetic moment and ##B## is the magnetic field. For a paramagnetic or diamagnetic particle...
  43. T

    I Origin of the Earth's magnetic field

    How can the motion of liquid iron consisting of neutral iron atoms in the earth's core create magnetic fields? What am I missing?
  44. Astronuc

    Plasma thruster - plasma instability in magnetic nozzle

    Plasma instability may be a solution for magnetic nozzle plasma thrusters https://phys.org/news/2022-12-plasma-instability-solution-magnetic-nozzle.html Kazunori Takahashi (Tohoku University), Christine Charles (ANU, Canberra, AU) & Rod W. Boswell (Tohoku University) Wave-driven electron...
  45. Ahmad Sadek

    B Can a rocket flame be controlled by a magnetic field?

    An idea came to my mind after I saw the plasma reactor and how the plasma floats through a magnetic cage that prevents the nuclear reactor from melting, to make a magnetic cage that prevents the rocket engines from melting while they are working. Is this possible, or does it take a critical...
  46. Drakkith

    Resources on Simulating Charges in Magnetic Fields

    Hey all. I started messing around with making a simulation involving charged particles moving in magnetic and electric fields and I was wondering if anyone had any good resources on the subject. I should be fine on equations, as I already have a book that should have everything I need about the...
  47. G

    I Magnetic Field vs Spacetime: Effects on Inertia Disk

    By following article a magnetic field can produce a least a minimum distortion in spacetime. If we have a inertia disk spinning 50% inside of a strong closed magnetic field may we suppose that we will create an unbalanced in the angular disc moment producing a propulsion without mass variation...
  48. PlanTer254

    B Magnetic fields attracting two disc-shaped magnets

    I had 2 small magnets in my mouth for distraction while working on something else,and I had this wierd question.the two magnets were not that strong,so just a force was easy to separate them with my teeth.then they would attract to be attached to each other and then the question hit me,the 2...
  49. alukhm

    Wood/Glass/Metal Magnet Inside a Shell containing Ferromagnetic Metal

    Hello all! I have a earring project with magnets involved but no magnet expert involved :( Here are a few stupid questions I hope someone can help us with! BACKGROUND: We are designing magnetic earrings. The earrings are meant to clamp the ear with 3 different levels of pressure. The magnetic...
  50. Lotto

    B What magnetic fields can this hollow rod shield?

    I suppose it can shield only the external magnetic field, not the field of the magnet itself. But I am not completely sure.
Back
Top