# Questions tagged [magnetostatics]

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### Why does a polarized material generate a depolarizing field?

I do not understand how a polarized material (steady state, no free current, no free charge) can generate a depolarizing field. Based on https://en.wikipedia.org/wiki/Demagnetizing_field, I "...
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### Magnetic field inside a ferromagnetic material

Let us suppose there is a block of a ferromagnetic material inside a very long ideal solenoid. We know that the magnetic field lines inside are always in a straight line which will be perpendicular to ...
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### Electrostatics and Magnetostatics as Field Theories ( isn't the Coloumb law depicting an instantaneous action at a distance)

Take the formula for Coloumb's law. It does not show in any case as to how the static field propagates. What I can feel is that the field of a static charge is ever prevading from the time the charge ...
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### Current Density as a 3D Function

I have a three dimensional current carrying coil. This coil has rectangular cross section, with a rectangular hole cut in the middle. The aim is then to assign the current density at points inside the ...
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### Why is the magnetic field due to an infinite current sheet constant throughout all of space?

By Ampere's Law, using a rectangle as an Amperian loop, I know that it can be derived that the magnetic field is constant throughout all of space (i.e. it does not depend on the distance r from the ...
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### Violation of Amperes circuital law

How does the magnetic field expressed in perfectly straight lines from a magnetic north pole to a south pole violate amperes law?(As my textbook says that it will ) On the contrary, what would make ...
375 views

### Find torque due to Lorentz force - Wrong result

Current I is coming from the Z axis and then it flows out uniformly towards the circumference of this disk. The disk has thickness t and Radius R. There is also a constant B field in the Z direction(...
Given a current density distribution $\mathbf J(\mathbf x)$ inside a closed bounded region $\Omega$, the magnetic field at any point $\mathbf y$ outside of $\Omega$ can be expressed as $$\begin{... 2answers 3k views ### What is the permeability of a permanent magnet? The following is a diagram that shows the B- and H-fields of a permanent magnet. Inside the magnet, the H-field is in the opposite direction to the B-field, because of the magnetisation M-field and ... 1answer 64 views ### Current density \mathbf{J} of particle with magnetic dipole moment \mathbf{m} [closed] I'm solving some excercises on magnetostatics, and encounterded this on which i'm having some trouble. Given a particle of magnetic dipole moment \mathbf{m}, show that its current density is given ... 0answers 51 views ### Why does magnet attract and push each other? [closed] Why do magnet attract and push each other? This question seems easy, but in fact, it is big, maybe as big as trying explaining gravity with quantum physics to the origin that how each particle ... 1answer 67 views ### Boundary Conditions in Magnetostatics - Calculating surface current density I'm working on a finite element simulation of the magnetostatic magnetic vector potential in 3D, with the following geometry:. The internal structure is a hollow cored-rectangular current loop. The ... 0answers 50 views ### Compute permanent magnet movement in magnetic field Assume I have tiny magnet particles in vacuum, which are not considered as a points, although they are very tiny. Magnet particles are situated in a uniform magnetic field. How can I can describe the ... 1answer 142 views ### Building huge magnetic field gradient Looking at how MRI works, I came across the fact that the spatial resolution depends on the magnetic field gradient, this gradient being created by "gradient coils". I was not able to find what the ... 0answers 69 views ### Magnetic field through ferromagnetic cylinder when length is much bigger than the radius? To preface, this is indeed a homework problem. I am a mathematician taking an electromagnetism module and have trouble wrapping my head around the problem at hand, and am struggling to start a ... 0answers 22 views ### magnetostatics and electrostatics orbiting an object with a field I understand from the Feynman notes on physics how a static magnetic field in one frame of reference becomes a static electric field in a reference frame in which I move at the same speed as the drift ... 1answer 46 views ### Coulomb gauge in magnetostatics should give divergence-free vector potential Say we're dealing with magnetostatics (\vec{\nabla} \cdot \vec{j} = 0 ). If we define \vec{A} to satisfy \vec{B} = \vec{\nabla} \times \vec{A}, and we take the assumption that \vec{\nabla} \... 1answer 829 views ### Moving charges and steady current Steady currents generates a constant magnetic field-magnetostatic Formally, this is \frac{\partial \vec{J}}{\partial t}=\vec{0} Any currents steady or otherwise are due to the movement of point ... 0answers 129 views ### Total current for an arbitrary current density Imagine a localized region \mathcal{R} which contains a current density \mathbf{j}, which we take to be divergence-less, \mathbf{\nabla\cdot j} = 0. What is the total current associated with ... 0answers 30 views ### How do I prove that the integral of a dot product of position vector and current distribution over all space is zero? I am currently taking intro electrodynamics. My professor showed us that the for a current distribution \vec{j}(\vec{r}), the following relation is true: \int d^{3}r' j_{k}(\vec{r}') = 0 And I ... 0answers 107 views ### Permittivity and electric Susceptibility intuition I have a question on the intuition behing the relation between relative permittivity \epsilon(\omega) and electric susceptibility, \chi_e of a of a material, more precise a dielectric medium. ... 6answers 859 views ### Forms of Maxwell's equations In my physics class, I was taught two forms of one of Maxwell's equations: Ampere's law$$\vec{\nabla} \times \vec{B} = \mu J$$and Maxwell-Ampere's law$$c^2\vec{\nabla} \times \vec{B} = \dfrac{\...
I start from $d\vec{F}=\nabla(\vec{m}\vec{B})$, $\vec{M}=\frac{d\vec{m_i}}{dV}$, and $\vec{M}=\frac{\chi_v}{\mu_o}\vec{B}$. I write out the definition of the force, determine we're only interested ...