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
34 views

Lorentz Force and Apparent Conservation of Momentum Violation Useful for Unidirectional Force?

My understanding is that the apparent violation of Newton's Third Law by the Lorentz Force necessitates a description of the system that describes the "missing" momentum as being absorbed/carried by ...
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4answers
87 views

Can light be warped by a magnetic field? [duplicate]

I was thinking and came up with the question "Can the path of a photon be warped by a strong magnetic field?" I tried searching online for an answer but couldn't find much scientific evidence of it ...
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2answers
33 views

What is filtered through the linear polarization of EM light? E field, B field or both?

I know that for EM waves (i.e sunlight) for any E wave in any direction, there is B field perpendicular to it. However, when we pass that EM wave through the linear polarization filter, what actually ...
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3answers
147 views

Why do charged particles follow magnetic field lines?

This may seem like a dumb question, but I can't think of the answer. The context I am curious about is the solar wind. Specifically particles flowing out of coronal holes and following the magnetic ...
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0answers
29 views

critical magnetic field superconductivity suppression in SQUIDs

Superconducting quantum interference devices are used as very sensitive magnetometers. However, on the wikipedia page, it claims that SQUIDS can be used to measure fields up to 7T. How can a device ...
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0answers
72 views

Magnetic field of a solenoid in a soleniod

I understand that using ampere's of an infinite soleniod is $$B = {\mu _o}nI$$. However, what if we have two infinite solenoids, where there's a solenoid of radius a and another of radius b. What ...
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1answer
116 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
88 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
29 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 $\vec{A}=Bx\hat{y}...
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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
56 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
106 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
77 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
69 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
29 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
32 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
257 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
95 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, and ...
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0answers
26 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
108 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
68 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
50 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
40 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 the ...
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1answer
69 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
135 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
189 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
160 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 ...
5
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2answers
477 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 \mathbf{J}(\mathbf{y})\times\frac{\mathbf{x}-\mathbf{y}}...
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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
561 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 ...
0
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1answer
67 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
62 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
46 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
60 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
24 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
61 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
79 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
157 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
41 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
14 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
83 views
1
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1answer
30 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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4answers
263 views

Maxwell Equations don't give unique Electric Field?

Consider the class of electric fields given by $$\mathbf{E}=\begin{cases} \ln (Cr)\hat{z} & 0\leq r < R\\ 0 & r> R \end{cases}$$ where $C$ is a constant and $r$ is the polar-distance ...
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0answers
41 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
14 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
189 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
118 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 ...