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.
For electric charges the relation is ##F=k\frac{q_1q_2}{r^2}##, where ##k=\frac{1}{4\pi\varepsilon_0}##. It seems to me that for the (hypothesized) magnetic monopole one could write an equivalent ##F=n\frac{p_1p_2}{r^2}##. I have replaced the q's with p's for "pole strength", and k with n --...
So hypothetically you bring a container into an MRI room. Inside the container is a USB drive, a crypto hardware token, an electronic tablet, and a Walkman.
Then you run the room's MRI machine, which has a magnetic field strength of 3 Teslas. What kind of container could prevent any...
Suppose there is very long current carrying wire. A charged particle is present somewhere around it. The current in the wire varies with time, thus by biot-savart's law there should be time varying magnetic field. I want to know that will this time varying magnetic field produce electric field...
Does anyone know how to calculate the coefficients for higher order (sixth and beyond) terms for the electron anomalous magnetic moment? I have a clear understanding of calculating the Schwinger term, but beyond that I cannot find anything in the usual QFT textbooks. The usual papers often...
My attempt at a solution:
Cylindrical coordinate system with ##r##, ##\theta##, ##z##. Conductivity ##\sigma## and permeability ##\mu_0##. Inner radius ##a## and outer radius ##b##. (##b>a##)
The external field is spatially uniform and driven at sinusoidally at frequency ##f##. The external...
https://physics.aps.org/articles/v17/117
Small one-quantum magnetic vorticies form in Type 1.5 and 2 superconductors. It was thought that such vorticies would confine the non-superconducting electrons inside them. This experiment shows that this is not the case. The vortex can move for the...
The updated BMW calculation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment aμ in the Standard Model is squarely consistent, at 0.9 sigma with the experimental measurement of muon g-2.
This agreement is found to be present despite the fact that its...
Assume i want to create a magnetic circuit within a ferrite core with airgap (i need the B field in airgap). The ferite core would have a coil on it. Problem is if i want my core airgap area and magnetic path length longer than wavelenght of current through the coil i would have high losses as...
First astrophotography was black and white. So then we colored it in. Then the light got filtered so people can see the universe better. When I ask why are there no photographs of magnetic field lines in space, or anywhere; I read that it's because our eyes cannot see them, but we can't see...
So, the formula for Gravitational force is F= Gm1m2/r^2
So a given mass such as the earth and a mass such as much self both contribute to an equal and opposite gravitational force on each other. But we can also think of it separately in terms of just the gravitional field generated. The Earth...
https://www.space.com/sun-magnetic-field-flip-solar-maximum-2024
I know theyre not the same physics. I just wondered if the the Suns 11 year polarity flip has any analogy to the flipping T-wrench effect.
The solenoid can be assumed to be a stack of rings of width ##dz## each where ##z:0\to-\infty## . $$i=nIdz$$ $$\sin\theta=\frac{R-r}{l}$$ $$\cos\theta=\frac{z+x}{l}$$ $$dB=\frac{\mu_{\circ}nIR d\varphi dz}{4\pi l^2}$$ Call ##\frac{\mu_{\circ}nIR}{4\pi}=\alpha## $$ B_y =\int dB\cos\theta ...
Hello,
Knowing that the loss cone for a symmetrical geometry is also symmetrical, I was thinking has anyone ever tried a magnetic mirror where the central magnets are circular but the end magnets that create the highest B field are instead flattened. Wouldn't a flat coil achieve a stronger B...
this is the figure in the question.The question can be solved by first finding the induced voltage (and then the induced current), and then we can find the force on each side of the wire due to the magnetic field and subtract them from each other (since the force on the upper and lower sides are...
There is a magnet in the shape of a hollow sphere. And the inner surfaces are all n-poles, and the outer surfaces are all s-poles. At this time, how is the magnetic field formed in the empty space of the sphere? There is no s pole for the magnetic force lines from the n pole to enter, so can...
Hi.
Does displacement current create a magnetic field by Biot-Savart? I googled and found contradictory answers.
Also, in the presence of an external magnetic field, is it meaningful to calculate a Lorentz force acting on displacement current? What does the force actually act on then?
A wire coinciding with the X-axis carries a current I1 in the direction of increasing x. A second wire is parallel to the Z-axis at a distance R, and carries a current I2 in the downward direction as indicated in the figure. The magnetic field at point P (0, 0, R) is: (options and diagram in photo)
A current current loop is running through this figure.
How do I design integration surfaces to find the magnetic dipole moment?
In the solution the three following figures were designed for integration surface, and they prove that they all give the same answer of ## m= 2IRd \hat{z} ##.
For...
What is the difference between magnetic field strength, magnetic field intansity and magnetic flux density. I have heard that MG intansity is independent of medium it represents the magnetizing power of a magnetic force
I use FLHR and the plan diagram. This suggests that the left hand side of the coil is going down. I have added annotations to this, which agree with the mark scheme which then goes onto suggest that the coil turns clockwise. To me though this would make it go anti clockwise.
So... what am I...
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?
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)...
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...
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?
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...
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
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)...
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...
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...
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...
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 =...
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...
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...
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.
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...
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...
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...
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?
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...
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...
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...
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)
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.