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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How does magnetic field affects a charge?

If a electron is placed in a fixed magnetic field, how the electron will get influenced by it? How does magnetic field attacts/repulses the charge?
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1answer
46 views

Magnetic monopoles and special relativity

I was thinking about magnetism as a product of special relativity and the result of this approach to the magnetic monopoles. So if magnetism is a product of electricity(like electricity from another ...
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62 views

Bar magnet dropped through coil

If you have drop a bar magnet through a coil so that it goes all the way through I was told the graph of emf induced in the coil vs time looks something like this: (emf induced is on y axis, time ...
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0answers
26 views

Do these symmetrical looking B field problems have the obvious answer?

I am struggling with two questions whose answers both appear to be trivially zero by symmetry arguments, when I was expecting more derivation to be required. Problem A), An infinitely long wire ...
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1answer
22 views

Faraday and Lenz's laws

in my revision guide it gives the equation for Faraday's law as $$\text{induced emf} = N\frac{\Delta \phi}{\Delta t}$$ while the one for Lenz's law is given $$\text{induced ...
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1answer
18 views

What is flux linking?

In my revision guide it says, "flux linking is when emf is induced by changing the magnitude or direction of the magnetic flux." I'm slightly confused here because earlier on the page it defines ...
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1answer
25 views

Fleming's left hand rule

in Fleming's left hand rule is the direction of current showing the direction of the flow of electrons or the direction of positive charge? Thanks
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2answers
51 views

Conducting rod moving through magnetic field

If a conducting rod moves through a magnetic field which way do its electrons move? In my revision guide it shows the following picture (more or less, but the following is my drawing of it -- I ...
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1answer
16 views

Notation Comprehension - Magnetic Field vector

While studying I've come in touch with a question about Magnetic Momentum, Torque and Loops. In it the following picture was given: During the calculus of the Torque, the intensity of the field and ...
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1answer
28 views

Interacting magnetic fields

Is there a reason why two magnetic fields perpendicular to each other do not interact? If they are parallel or at a non-90 degree angle they interact. Is it because magnetic field lines can be viwed ...
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2answers
38 views

Why does one call $B$ the magnetic induction?

When one studies electrostatics we have the electric field $\mathbf{E}$. This object usually is introduced as a field produced by a configuration of charges such that the force on another charge $Q$ ...
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2answers
40 views

Could I make a magnetic foam or film by mixing magnetic dust?

I'm a developer and tinkerer more than an academic, and I'm not sure if this question, being more practical and less theoretical, will be welcome or not here. But here goes, with apologies in advance ...
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1answer
46 views

Do the relations between E/B and D/H contain higher order multipole terms?

Jackson writes in section 1.4 (third edition) that \begin{align*} D_\alpha &= \epsilon_0 E_\alpha + \left(P_\alpha - \sum_\beta \frac{\partial Q'_{\alpha\beta}}{\partial x_\beta} + \ldots \right) ...
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1answer
31 views

Do changing magnetic fields always produce solenoidal electric fields?

Since the curl of E is the time derivative of B, $\nabla \times \vec{E} = -\frac{\partial B}{\partial t}$ Do changing magnetic fields always produce solenoidal electric fields? For instance a ...
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0answers
24 views

Meissner effect and levitation

In a field less than critical field, decreasing the temperature below the critical temperature will eliminate the magnetic field inside a superconductor and increase the magnetic field around it. ...
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1answer
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Description of the motion of a charged particle attached to a spring [closed]

A particle with mass $m$ and charge $q$ move in the $xy$ plane and is attached to an ideal spring with neglectable mass, a spring constant $k$, rest length $r_0$ and a magnetic field $B = B_0z$ is ...
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2answers
46 views

what is the result of change in gravitational flux?

As a change in magnetic flux results in induced EMF (electromotive force) likewise what is the result of a change in gravitational flux? UPDATE: Gravitational flux according to me has only ...
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0answers
27 views

Can we use the geomagnetic field to power something? [duplicate]

My question might sound idiotic, but I could not help it: Can we harness the earth's geomagnetic field to repel another magnet in such a way that we can get some motion out of it?
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1answer
25 views

Magnetic field from a point charge: in which reference frame is the velocity vector defined?

The magnetic field generated by a point charge is given by $\vec B =\frac{\mu_0}{4\pi}\frac{q \vec v \times \hat r}{r^2}$ I understand that $\hat r$ denotes the unit position vector with the point ...
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2answers
33 views

what does magnetic field vector mean?

I am trying to understand what a magnetic field vector tells us about the magnetic field. I understood that a vector is just a representation of a point and how much it is moved in x,y and z direction ...
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1answer
34 views
+50

What really happen with resonance inductive coupling

I can't figure out the picture of resonance inductive coupling I can image how magnetic inductive coupling works, It scatter magnetic around one coil and if second coil being near it then induce ...
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3answers
56 views

Electromagnets, and how $H$ is the thing we set on the dial

Let's say that I have an electromagnet, consisting of Helmholtz coils with an iron core. David Griffiths, in his "Introduction to Electricity & Magnetism" text claims that $H$ is what we set, by ...
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1answer
24 views

Induction Oscillation [closed]

A bar (m=100g, l=10cm) is moving in a constant magnetic field $B$ as shown above. The resistor $R$ is $1\Omega$. The bar is attached to a spring with spring constant $10N/m$, can you derive ...
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1answer
62 views

How much external field have to be applied to saturate a Mu metal shield till magnetization?

My main goal is to magnetize and demagnetize a Mu metal shield. Till now I am using a Helmholtz coils setup and I can generate 10 mT applying 2 A DC. I am using a DRV425 fluxgate and a hall probe ...
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2answers
43 views

Spin State Energy Levels

When a spin-1/2 particle is placed in a magnetic field that is strong enough and varies slowly enough in space and time, it will become polarized and its spin will either align or anti-align with the ...
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1answer
30 views

Why does the Magnetic Flux Density B, saturates in a ferromagnetic material with increasing H?

I understand that the magnetization must saturate as more and more domains are aligned. But $B$ is still directly proportional to $H$, and hence it must increase linearly with $H$. But every book ...
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0answers
20 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
62 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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0answers
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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
69 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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1answer
44 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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2answers
39 views

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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2answers
87 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
51 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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0answers
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
16 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
52 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
47 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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0answers
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
48 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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0answers
14 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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0answers
29 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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0answers
31 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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0answers
76 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
24 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
39 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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0answers
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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
48 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 ...