# Questions tagged [magnetostatics]

The study of magnetic fields in systems where the currents are steady (not changing with time). It is the magnetic analogue of electrostatics, where the charges are stationary.

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### How to interpret Magnetic Susceptibility as the ratio of two vectors $M$ and $H$, as division of two vectors is not defined in mathematics?

Magnetic Susceptibility, denoted as χ is defined as a scalar, represents the ratio between the Magnetization vector ($\vec {M}$) and the Magnetic field strength vector ($\vec{H}$). However, in ...
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### If the conductor floats in a horizontal homogeneous magnetic field, what is the current?

If the conductor floats in a horizontal homogeneous magnetic field, its magnetic flux density is 0.75 T and one meter of conductor weighs 2.5 g. How to calculate current. So when the length or mass is ...
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### Which electromagnetic coil would have a stronger magnetic field, High amperage low voltage or low amperage high voltage?

My apologies if the question is just too simplistic, I asked to ChatGPT and it said that the high amp low volt coil would be the strongest, I just want to confirm. Assuming that both have the same ...
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### Still can't see why $\nabla \times \mathbf J(\mathbf r') = 0$ in Biot-Savart derivation

When deriving the differential form of Biot-Savart's law (which is also Ampere's law under magnetostatic conditions) there is one step which I am still not fully convinced. We will firstly use this ...
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### Computation of surface bound current: ambiguity in the choice of a normal unit vector for a surface

Let us suppose to have two coaxial cylindrical tubes, namely two cylindrical surfaces $\Sigma_1, \Sigma_2$, with a radius of $a$ and $b$ respectively. A current $I$ flows across the surfaces but in ...
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### Force on infinitesimal loop as stated in Griffiths' Electrodynamics

I've found little to no success in finding a proof of result given by Griffiths at the start of the chapter on Magnetic fields in matter, namely the one for the force acting on an infinitesimal loop ...
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### Force on a circular loop formulae in Griffiths' Electrodynamics

I'd like to ask for some clarifications on the formulas for the force on a loop with magnetic dipole moment immersed in a non-uniform magnetic field, given by Griffiths in Introduction to ...
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### Torque on a current loop in a uniform magnetic field

I'm trying to prove the result the net torque on a current loop in a uniform magnetic field is $\vec{\tau}_{net}=\vec{\mu}\times \vec{B}$ where $\vec{\mu}=I\frac{1}{2}\oint(\vec{r}\times d\vec{r})$ ...
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### Derivation of discontinuity of vector potential

I'm trying to prove the equation from Griffiths' Introduction to Electrodynamics which tells us that the vector potential ${\bf A}$ is continuous across any boundary (both tangential and normal ...
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### Magnetostatics: Boundary conditions

I'm reading chapter 5.4.2 of Griffiths' Introduction to Electrodynamics, and I'm having trouble understanding some of the reasoning and some of the results he obtains. He starts by considering a ...
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### Point dipole approximation limit

Can I approximate the field of a 10 mm length x 5 mm radius cylindrical magnet at 8 mm away using a point dipole approximation? I was wondering if it would still be possible to create a semi-accurate ...
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### Metals and Magnets

A metal is attracted by a magnet when placed in it's vicinity. I was wondering if it is the metal that moves towards the magnet, or is it that both the metal and magnet move towards each other? Could ...
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### How can magnetic materials be practically represented in magnetic vector potential?

The magnetic field can be represented in terms of the $H$ field and the magnetization field, often with the magnetization field condensed into the relative permeability constant $\mu_r$ by assuming it ...
1 vote
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### Magnetic field outside of permanent magnet - What is $\vec H$?

If a cylindrical magnet has a uniform magnetization $\vec{M}$ along its axis its magnetic field $\vec{B}$ looks approximately like this: There seems to be a contradiction to me. Since there are no ...
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### Biot-Savart integral over a half-ellipse does not seem to approach the result on the line

I am trying to compute a Biot-Savart integral of the vector potential over one-half of an elliptic path, however as a check I compared the result when the ellipse becomes "squashed" as an ...
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### Does this basic example of two bar magnets preserve angular momentum conservation?

Let's say I hold two bar magnets side by side both vertically aligned ($z$-axis). I don't want to worry about their shapes, so let's approximate them as dipoles. I will use the dipole formula rather ...
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### Biot-Savart for two infinite wires with U turn

Consider this arrangement ...
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### Ampere's law on infinite path

I was calculating the magnetic field of a circular current loop using Biot-Savart law and obtained it straightforwardly. If the loop is in the $xy-$plane, centered at the origin, the field at a point ...
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### Confusion on Griffith's Electrodynamics Example 5.3

In the fourth edition of Introduction to Electrodynamics, a scenario is described in example 5.3 where a rectangular loop of wire supporting a mass $m$ hangs vertically with one end in a uniform ...
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### What are the necessary conditions for a current to be steady?

Does the divergence of the volume current density have to be zero for the current to be steady? If so, what are other other conditions? If not, what are the conditions for a steady current in general?
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### Can you magnetize iron by putting it in the air gap of a two parallel plates capacitor?

We can magnetize an iron piece (i.e. permanently given enough field strength) by putting it inside a solenoid strong homogeneous field and charging/discharging the solenoid several times. I am asking ...
1 vote