For questions that utilize the concept of magnetic fields (commonly denoted by the letter B), or for questions whose answers likely involve magnetic fields. More specific than the [tag:magnetism], as questions about the phenomenon & theory of magnetism do not necessarily involve the discussion of ...

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Conservation of energy for transformers in AC current

I tried to solve a set of differential equations for transformer on AC Current. But at the end it seems that my solution does not satisfy conservation of energy. I spent days try to find a mistake, ...
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18 views

Magnetic levitation manipulation

Suppose a small crystal or mineral piece with a completely known structure was held by magnetic levitation. Would it be possible to orientate the piece by manipulating the magnetic field so that a ...
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2answers
54 views

Why doesn't a magnet on a refrigerator slide down?

Obviously gravity pulls objects towards the earth's surface. Now suppose I have a refrigerator and a magnet. The magnetic force is perpendicular to the gravitational force. So it is not counteracting ...
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What happens to magnetic $B$-field in a superconductor in the Bean model?

In the Bean model, as we start applying a magnetic field $H$ in the plane of a slab, the $B$-field inside the superconductor decreases linearly from each side, and at a sufficiently high field $H^{*}$ ...
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1answer
68 views

Does elementary particle emit photon?

Charged particles are accelerated by the magnetic field in a particle collider before allowed to smash together at specific location where the detectors are housed. My question is do the ...
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154 views

JEE MAIN 2015 Question. Electromagnetism [closed]

Two coaxial solenoids of different radii carry current I in the same direction. Let F1 be the magnetic force on the inner solenoid due to the outer one and F2 be the magnetic force on the outer ...
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34 views

How to calculate earth's magnetic field by time period of suspended magnet?

Assuming that torsion of the suspension wire small enough to be neglected, how can we derive earth's magnetic field by measuring time period of an oscillating magnet suspended on a string?
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Why doesn't current induced by changes in flux affect the flux, while current induced by a battery does?

Faraday's law states $V=-\frac{\mathrm{d}F}{\mathrm{d}t}$, where $F$ is flux. Since $V=IR$ for passive circuits, $I = V/R = -\frac{1}{R}\frac{\mathrm{d}F}{\mathrm{d}t}.$ But by the Biot-Savart law, ...
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80 views

Derivation of Jefimenko's Equation in Jackson's EMT book

I have been trying to understand the derivation of Jefimenko's equation in Jackson on p.246-247 which can be seen in the photographs attached. First of all I did not fully comprehend the ...
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1answer
50 views

Why do really powerful magnets have to be really big?

If you want to make a really powerful magnet, that can for example attract golf ball sized metal objects from 15 feet away, the magnet has to be really big, and really heavy. Why is this so? I don't ...
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22 views

A magnet's magnetic field strength

Assume that we have six horseshoe magnets which are equivalent in every manner. If we put them together by stacking perpendicularly, what could be said about that magnet assembly in terms of its ...
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1answer
14 views

What are the general rules for determine on which two ends of a bar magnetic are its poles located?

I am wondering. Maybe somebody be nice enough to put a explanation that doesn't involve too much math. I did notice that for bar magnets, their poles are not always on the two ends separated by the ...
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1answer
48 views

Why does a real/virtual photon interact only with charged particle?

A photon is the force carrier of an electromagnetic wave and it consists of an electric and a magnetic field propagating through space at the speed of light in vacuum. It exhibits wave-particle ...
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2answers
38 views

Is this a possible monopole setup, or will it cancel out? [duplicate]

Suppose you have a ball that is covered in magnets, in which the North Pole of every magnet faces outward. Is this a monopole? Or at least "functions" as a monopole? And what will happen if you placed ...
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1answer
65 views

Shouldn't the currents be time-continuous here?

My intuition is that the current upon an inductor (say, a solenoid) will always be time-continuous, without "sudden changes". But below is a case that seemingly contradicts this point of view. There ...
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1answer
46 views

Special relativity, electromagnetic fields, charge and Q

Is it true, were Coulomb's constant k to be several orders of magnitude smaller, that there would be no (or increasingly negligible) magnetic fields generated by moving charges? The reason being the ...
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10 views

Gradient of a normalized hysteresis loop in longitudinal geometry

I am thinking what is the gradient of a normalized hysteresis loop in a longitudinal geometry. I think it is the gradient of the normalized energy density of the system in the uniaxial situation. ...
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2answers
46 views

Are magnetic field lines level sets?

I have been learning a bit about level sets. After doing this, I looked at a diagram of magnetic field lines and noticed they don't intersect rather like the lines on closed curve level sets. My ...
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13 views

How much drag/friction does moving a magnet past coil make?

In the pic below in Fig . 1 I understand this as a very crude way of generating an electrical charge / voltage in the wire if the magnet shown is moved along the length of the wire.. In Fig.2 there ...
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28 views

How can you visualize hard axis of magnetization?

I think the main problem here is my understanding of the hard axis of magnetization. The hard axis is the "bad" direction of the magnetization i.e. the direction inside a crystal, along which large ...
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28 views

How to repeat the Biot-Savart experiment for the direct current in a straight wire and the corresponding magnetic field without side effects?

As I read Biot and Savart took a compass needle and this needle make some rotation when the current was switched on and off. As it was clear that a changing current induces a magnetic field the ...
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69 views

Force between two current carrying wires: the general case

Assume two straight current carrying parallel wires with currents ($I$ and $I'$) flowing in the same direction, at a distance $R$ from each other. From Ampère's law (and from Biot-Savart as well) it ...
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2answers
23 views

Limits of Integration Trig, Mag Field Infinite Length Wire

I don't understand how the limits of integration should be defined when doing basic integrals of trig functions. It seems like it's an arbitrary decision, I don't understand it. Here's the set up: ...
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1answer
33 views

How does the magnetic field generated from a rectangular cross-sectional current-carrying conductor differ from a circular cross-sectional conductor?

I can find much information of cylindrical conductors (ie. regular wires), where $B=\frac{\mu_0 i}{2 \pi r}$ and $r$ represents the radius (or distance) from the centre of the conductor, however I ...
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15 views

Two circles in uniaxial anisotropy and remanence plot?

I am thinking how you can show that there are two perfect circles separated by $\delta$ in an uniaxial anisotropy with the material CoFeB; here a draft practical case data about them The general ...
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1answer
46 views

Do magnetic fields cause ionisation of gases?

I am doing my final year engineering project on Magnetic Field Assisted Combustion and was curious to see what people thought about it. Companies sell rare earth magnetic arrangements to be attached ...
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1answer
60 views

Induced magnetic field produces electric field and vice versa forever!

So here are the two of Maxwell's laws that I am interested in: So we have the simple circuit (from google): So, before the system goes into steady-state we know that charge slowly accumulates on ...
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3answers
590 views

Would a spinning, evenly charged sphere generate a magnetic field?

I could see how it would go either way. On the one hand, there IS moving charge; on the other hand, it is not discernibly moving.
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3answers
624 views

Why should Conservative forces have their curl equal to zero?(intuition)

There are several conditions that must be met in order for a force to be conservative. One of them is that the curl of that force must be equal to zero? What is the physical intuition behind this? If ...
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26 views

Magnetic field of cylinder equal to two current loops?

I was reading a text about the magnetic field of a uniformly magnetized cylinder when I came across this. The author states that since \begin{equation} A_{\phi}(\rho,z) = \frac{\mu_0 a M}{4\pi} ...
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20 views

Is the electron's magnetic dipole moment influenced by the measurement method?

The electric charge of an electron at rest is a constant value and is not influenced by the measurement instrument. The measurement instrument by itself can give more or less accurate result, but does ...
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3answers
6k views

Why doesn't light affect a compass?

In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
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1answer
51 views

Right hand rule confusion

I have a question that I am trying to figure out: Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right ...
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1answer
65 views

Force between two finite parallel current carrying wires

Remark: This is not a homework question...It is pure out of theoretical interest. I asked this the mathematics-community a couple days ago and got no answer, so I figured I'd try here. Most standard ...
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1answer
113 views

Using a circuit to make a magnetic balance to weigh objects

I understand that this is a homework question, but I am learning about magnetic fields and things like that and this certainly wasn't covered in the material, so my question is more about the actual ...
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1answer
44 views

magnetic field due to current in a wire using Biot-Savart's law

I am learning about Biot-Savart's law to calculate the magnetic field due to the electric current in a wire. ...
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0answers
17 views

Field in a toroid

How does the field change in the cross section of a toroid? I will give you my attempt at an answer so that you can see what I am trying to ask. I think the field should look something like this: ...
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34 views

Magnetic susceptibility in ising model as magnetization change

Let's say I have a standard 2D Ising model with $$ H(\sigma) = - \sum_{<i~j>}\sigma_i \sigma_j - h\sum_{j} \sigma_j $$ With the metropolis algorithm, I can compute various things like energy ...
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1answer
33 views

Repelling a weak permanent magnet with an electromagnet

I have a question about magnetic repulsion. Suppose I have a permanent magnet (axially magnetized) placed on top of the iron core of an electromagnet. I want to switch on the elctromagnet to repel the ...
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1answer
26 views

Why does magnetic flux linkage become negative when a coil is turned through 180degrees?

Taking a rectangular coil, in a constant magnetic field, it is understandable that BANcos(theta) should apply for the magnitude of the flux linkage. However if the coil is turned through 180 degrees ...
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3answers
189 views

Spin in magnetic field and eigenvalues

We have some arbitrary quantum state, lets say $$\vert\Psi\rangle=\alpha_{1}\vert\uparrow\rangle+\alpha_{2}\vert\downarrow\rangle= \begin{pmatrix} \alpha_{1} \\ \alpha_{2} \\ \end{pmatrix}$$. And ...
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2answers
63 views

Magnetism: why is a steel ball-bearing repelled from a magnet towards a piece of unmagnetised steel?

At the risk of sounding like one of the Insane Clown Posse, I was watching this video of the late Eric Laithwaite discussing magnetism: Eric Laithwaite, Circle of Magnetism (1968) (the relevant ...
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1answer
27 views

Magnetic Field Along the Axis of the Current Ring - Alternative way to compute

This is Example 5.6 in Griffith's Introduction to Electrodynamics (4th Edition): Find the magnetic field a distance $z$ above the centre of a circular loop of radius $\ R$, which carries a steady ...
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23 views

How to find magnetic moment using android sensors?

I am working on android application which analyze magnetic field and should find position of magnet in predefined space. I am using for development permanent magnetic dipole and android sensors ...
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1answer
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Can an electric current's magnetic field be represented by a magnet/magnets?

Is it possible to recreate the exact same magnetic field that electric currents have with a magnet and if it is, how?
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4 views

Magnetization Curve of the Coiled Tube HS-90

Could anyone provide the magnetization curve (B-H curve) of the Coiled Tube HS-90, which is made of steel alloy A-606 type 4 molly? Thank you.
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1answer
157 views

Is Magnetic Field is made of Photon? Is there any frequency of Magnetic Field waves? [duplicate]

(Considering the What is a magnetic field question which is asked on just 8th march, by @DragonSlayer3 and my own question which is left with negative points and closed, Photon Energies in sunlight, ...
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26 views

How can I compare magnetism/mass ratio of different magnets?

I want to compare the magnetism/mass ratio of different magnets. Let, for example be ceramic/samarium-cobalt/alnico/steel/neodymium magnets. Questions: What units should I compare for ...
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3answers
162 views

Question about magnetic force

I have some confusion regarding the magnetic force. I know that the magnetic field created by a moving charge or current EXERTS a force on any moving charge or current that is present in the field. ...