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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1answer
103 views

Magnetic Potential Energy

Does a charged rod or a shell have a magnetic potential energy when it is kept in a uniform magnetic field? Also, can anyone quantitatively explain why a wire loop carrying current would tend to be ...
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1answer
74 views

Landau levels in 2D

I seem to be having a very basic misunderstanding of Landau levels in 2D. Consider the derivation give on page 7 here, where we consider electrons free to move in 2 dimensions, with a magnetic field ...
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0answers
22 views

2D electron gas in magnetic field

I am trying to understand the derivation for the wavefunctions and levels of free electrons 2D in a perpendicular magnetic field. The usual prescription is to take a vector potential ...
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0answers
28 views

How does winding a coil always in the same direction affect its magnetic field when current is applied?

My old teacher told us that, when we are winding a coil to make an electromagnet, if we start for example from left to right, once we reach the right, instead of start filling the next layer from ...
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1answer
47 views

Net magnetic field of parallel wires with the same current flow?

Assume 6 wires separated by insulators of the same dimension, having the same current flow $I$ parallel to one another illustrated via this diagram: Due to the current flow in each individual wire, ...
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0answers
68 views

Electric field inside the “Dees” of a Cyclotron and why no “Cups”

I read about cyclotron and how does it work. Several references say that the particle to be accelerated is only accelerated when it is between the gaps of the "Dees" or the semicircular disc like ...
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1answer
60 views

Do plasmas have their own magnetic fields?

Do Plasma generate a magnetic field of their own ? Can they cause electromagnetic induction?? For example if a hydrogen plasma is ionized and its electrons removed.. And the protons accelerated ...
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4answers
3k views

Can we stop moving bullets by Eddy currents? [closed]

My idea is to make a gun-like model which would be the source of a changing magnetic field so that Eddy currents are produced in the bullet. Would it be enough to stop a moving bullet? I'm posting a ...
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1answer
60 views

Broken magnet pieces repels each other

Why the broken magnets can't be joined together? What happens to the broken sides in terms of magnetic poles?
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0answers
28 views

How to measure the magnetic moment of a bar of magnet?

I'm working on something and I need to calculate the force which is exerted on a magnet when it's put in a magnetic field I know the magnitude of magnetic field. So, the only thing I need is to ...
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0answers
28 views

magnetic field in simple train [closed]

I would like someone to check this image waynesthisandthat.com/images/HT%20994. jpg and be extremely kind and explain how to figure out which end of battery becomes north and south in simple electric ...
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2answers
249 views

Brownian motion moving nano/micro coils inside a magnetic field

Following experimental setup. We take copper coils which are small enough to be subject to brownian motion. We combine those coils with some other material to make them about as heavy as the liquid ...
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1answer
25 views

Whats is the relationship between energy of an atom and its magnetic moment?

I'm working on a problem that says that If $\varepsilon_{\pm}=\mp (\mu \mu_0 H + k \theta \frac{M}{\mu N} )$ is the energy of the atom of a specimen that can orient itself either parallel or ...
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1answer
88 views

Spin $1$ vs. spin $1/2$

A crystal contains $N$ atoms which possess spin $1$ and magnetic moment $\mu$. Placed in a uniform magnetic field $B$ the atoms can orient themselves in three directions: parallel, perpendicular, ...
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0answers
22 views

Repelling Force of a Magnet

I am trying to invent something that utilizes magnets, but I've come across a dilemma. Two magnets need to repel each other with a strong force. So my question is: If a magnets holding force is 71lbs ...
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2answers
99 views

Why don't the iron filing all goes to the North pole?

I always see images of simple experiment with iron filings and a bar magnet where the iron filing conform to the magnetic field to visualize the field lines. I do not understand why, under the ...
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0answers
61 views

Why does the side of two magnet attract?

I have two magnetic bars and when they are brought close sideway the two bars join where the two South poles are adjacent to each other, and so does the two North poles. If the magnetic field goes ...
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0answers
48 views

What's the equation for the magnetic field created by a single moving electron?

Suppose we have an electron moving in a straight line with velocity $v$. My question is: What is the equation that describes the magnetic field generated by this movement. I'm unsure how to proceed ...
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1answer
37 views

Switching off Magnetic Field [closed]

A line charge (charge per unit length 'k') is put onto rim of wheel of radius 'R' which is then suspended horizontally, so that its free to rotate (spokes are made of non conducting material). In ...
4
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1answer
66 views

Domain Structure and Ferromagnetism and Reversal of Polarity

According to the domain theory, Ferromagnetic substance when kept in the external strong magnetic field, it undergoes magnetisation by Rotation and becomes a permanent magnet thereby even after ...
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2answers
110 views

Why are magnets in form of hollow sphere not a magnetic monopole? [closed]

If I place many micro-bar-magnets on the surface of hollow sphere such that the pole of every magnet points towards the same side then, you could imagine that a monopole would be produced. So, I just ...
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2answers
142 views

Velocity selector and charge to mass ratio of an electron

I recently read that J.J. Thompson used a velocity selector to find the charge to mass ratio of an electron. Having learnt the principle behind the velocity selector, I see no relation between these ...
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2answers
109 views

How does magnetism work? (Not asking what magnetism does)

To clarify, if I asked "how does electricity work" I would want "electrons flow from a negatively charged area to a positively charged area", not "it powers electronics like phones" as an answer. The ...
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2answers
468 views

Proof of Ampère's law from the Biot-Savart law for tridimensional current distributions

Let us assume the validity of the Biot-Savart law for a tridimensional distribution of current:$$\mathbf{B}(\mathbf{x})=\frac{\mu_0}{4\pi}\int_V ...
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1answer
59 views

Cold Solid Matter at the End of a Black Hole's Acceleration Disk?

Is it possible that black holes magnetic field are rapidly cooling matter using a type of magneto caloric effect and cold fusion creating new matter only possible with a black hole's gravity? A type ...
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3answers
328 views

Helical motion of charged particle in external magnetic field

When an electron moves in uniform external magnetic field, with velocity not perpendicular, I understand that the magnitude of force is only due to the perpendicular component of velocity and is ...
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1answer
65 views

Ferromagnets - Permanent?

When researching about the Curie-Temperature and magnets in general, something got me confused. What is the difference between a ferromagnet and a permanent magnet? In a ferromagnet the spins are ...
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0answers
53 views

Radius of solenoid on the magnitude of magnetic field

I'm working on a project and have made a solenoid. I want to know the effective parameters on the magnitude of the magnetic field. $$B=μNi$$ In this equation, the radius of the solenoid don't have any ...
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0answers
35 views

Magnetic field of one electron

I want to reproduce a calculation of the magnetic field at the atomic nuclei produced by one electron in hydrogen: Maxwell gives us: $\vec \nabla \times \vec B = \mu_0 \vec j$ Doing the surface ...
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0answers
39 views

Data analysis for a magnetic hysteresis loop

I'm a physics undergrad and I have MOKE data for a magnetic material (thin permalloy film on a silicon substrate). Here is one of the hysteresis loops I obtained, plotted using python: The form of ...
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1answer
51 views

Eddy current induce emf

Q1Suppose there is a wire having AC current so as ac current is alternating it creates back emf wether that back emf produces current ?? If yes then that current is same as eddy current or not?? ...
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0answers
21 views

Magnetising a hollow steel ball from inside

Suppose a hollow iron/steel ball is magnetised from the inside by placing a magnet inside. Will the magnetic field on the outside of the steel ball be fairly uniform? Does anyone know if there's any ...
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3answers
55 views

relation between amplitude and frequency of a rotating electric field [closed]

I generated a rotating electric field produced by Ex=cos(wt) Ey=cos(wt-pi/2) in x and y directions. I ran a simulation and seems only in certain amplitudes and frequencies it makes a rotating field. ...
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0answers
44 views

Magnets levitation stability

I'm willing to make a levitating stand based on standard magnets. Both the stand itself and the levitating object would have magnets attached, of course the same poles heading each other. I have two ...
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2answers
129 views

Energy stored in magnetic field [closed]

I have encountered the problem: Find the magnetic energy stored inside a 1m length of wire carrying 10 amp. The wire is 1 mm in radius, and the current density is uniform. I have found a solution ...
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1answer
39 views

$\mathbf{J}$ and $\mathbf{E}$ having the same direction [closed]

Ohm's Law States that $\mathbf{J} = σ\mathbf{E}$ this implies then that $\mathbf{J}$ and $\mathbf{E}$ have the same direction . But we know that $\mathbf{E}$ in normal to a conductor and $\mathbf{J}$ ...
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0answers
13 views

Effect of removing material on Magnetization

I realized recently I have some confusion over $\bf{H}$,$\bf{M}$, and $\bf{B}$. Consider some infinite thin plane with permeability $\mu$, and say I know everything else there is to know about it. ...
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2answers
73 views
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1answer
28 views

Experiment on magnetic line of force

Say hypothetically the electrical current is flowing through the solenoid which is wrapped around a colossal electromagnet which is approximately 1 lightyear long. (Assume there is no resistant so no ...
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0answers
37 views

What's “the” physical explanation of hysteresis in ferrimagnetic materials?

I am wondering what is "the" or "a" physical explanation of hysteresis in ferrimagnetic materials. From what I've read in wikipedia and Cullity's book, there is a simple physical explanation for ...
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0answers
12 views

Field line Direction and exerted force

Magnetic field lines of a magnetic field have different directions. What information about the force exerted on a charge will give us the direction of field lines?
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2answers
158 views

How can I use a magnet to lift a paperclip?

This question has been asked already, but no satisfying answer came up. All the answers seem to push the problem further, but do not explain clearly what is going on. I will reformulate it for a ...
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1answer
96 views

Force on a magnetic dipole due to a magnetic field

Imagine a solenoid which has current $i$ and is producing a magnetic field $B$ which equals $$B=\mu N i$$ Now, imagine we put a small cylindrical magnet at the end of the solenoid. Then because at ...
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2answers
158 views

Super massive Black Hole and photon reduction [closed]

This is a picture of 2 galaxies taken from The Hubble. The arrow shows a smaller galaxy's black hole starving of the usual stars because of the binary rotation about the bigger galaxy that is pulling ...
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0answers
51 views

Force Exerting on a magnetic train

A question is already asked ( How does this “simple” electric train work? ). But I've got a question about it. In order to calculate the force which is being exerted on the system including magnets ...
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1answer
39 views

Where does the earths magnetic field originate [duplicate]

To my knowledge my knowledge magnetism comes either from an electric current flowing through an object or from a permanent magnet which can be created by heating certain ferrous metals to specific ...
3
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1answer
41 views

Analogue of charge for magnetic fields?

Now, I understand how there are no magnetic monopoles, and hence no analogue of magnetic charge in terms of a scalar field, but is there a similar concept that instead uses a vector or spinor field to ...
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0answers
32 views

Do metal shavings affect the magnetic field they are used to visualize?

It's obvious that the use of metal shavings to visualize magnetic field lines was instrumental in Faraday's work to develop electromagnetic theory. But they also did too good a job of convincing ...
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2answers
97 views

How virtual photons give rise to electric and/or magnetic field? [duplicate]

Say a neutron which have magnetic moment despite carrying no charge. Isn't both the electric field and magnetic field consist of virtual photons? So how can the same virtual photons give rise to 2 ...
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0answers
23 views

Magnetic Forces and Junkyard Magnets: What's Going On? [duplicate]

In my electromagnetic theory class, I learned that magnetic forces do no work. This is easy to see when observing a cyclotron; the speed never changes, so the kinetic energy never changes and ...