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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2answers
45 views

Magnetic field due to current, I don't get how you get the direction, can someone draw it for me? [closed]

Taken from here, 3rd problem. As you can see, no matter from which point current goes, from a to b or from b to a, in either cases, magnetic field would be down, right?
0
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1answer
106 views

How is magnetic field created in an atom according to quantum model

How is magnetic field created in an atom according to quantum model? I mean, we are taught about the magnetic field by bohr's model which assumes that electron revolves around the nucleus in a ...
0
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0answers
36 views

If I know how many atoms I have in a film, can I know the total magnetic moment?

Say I have a Co film and I know its volume so I know the total number of atoms in it. Using this plus the knowledge that each atom has a magnetic moment of 1.7 Bohr magnetons, would the total magnetic ...
1
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1answer
116 views

Why does transformer winding need large numbers of turns?

In transformers there are large number of turns in winding for both primary and secondary sides around the core. So, my question is why can not we just put one or two turns in winding as we need to ...
1
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2answers
62 views

Magnet and needle

When I place a needle near a clamped magnet and let it go, it moves towards the magnet. Since magnetic field cannot work on individual charge particles, we must conclude that the needle loses its ...
0
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1answer
71 views

A confusion with solenoidal windings

I have seen in solenoids, toroids, transformers, electromagnets and machines that the core is pretty insulated. Over this the winding coil is wrapped but it is a bare coil (turns are not insulated to ...
3
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0answers
53 views

Can a magnetic lock be negated or overcome by a stronger electro magnet? [closed]

Magnetic locks seem to be fairly standard on modern buildings. Is it, though, possible to negate a magnetic lock my placing an oppositely-polarized, strong electromagnet across from the magnets on the ...
1
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2answers
49 views

How does this incorrect model of a wire give the correct result for B-field produced?

I see in Griffith's book Introduction to Electrodynamics, 4th edition, the following model (paraphrased). Consider a wire (infinitely-long) with positive linear charge-density $\lambda$ moving to ...
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3answers
75 views

development of magnetism in a magnet [closed]

If we cut a magnet, the magnetic field develops. But if we cut it vertically, then will the magnetic field develop?
4
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1answer
58 views

Why do these calculations of EM fields for a magnet and wire loop seem inconsistent?

Suppose you have a conducting circular wire loop and a magnet moving towards each other. They move along the $z$ direction with nonrelativistic constant speed $v$. Let the $B$ field of the magnet in ...
2
votes
1answer
66 views

Why a motionless proton doesn't feel any force in a magnetic field according to special relativity?

In this ( https://www.youtube.com/watch?v=1TKSfAkWWN0 ) specific video uploaded by Veritasium on YOUTUBE , we come to know about how special relativity makes magnets work. We observe that when a ...
40
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4answers
6k views

Is Earth really a magnet?

I am a student of class 9. When I was going through magnetism and read that an earth is a magnet I got some doubts. My question is: is earth really a magnet? Doesn anyone have any proof that earth is ...
2
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1answer
58 views

How to define a the outward direction of 4d simplex?

For a 2d simplex (triangle) with three vertices a,b,c, we could define the outward direction of the face as a-b-c, like define a magnetic field induced flux. For a 3d simplex (tetrahedron) with four ...
1
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0answers
51 views

When a coil makes a complete turn, why is does magnetic flux double with respect to time?

EMF, $\mathcal{E}$, is equal to -d($\phi$)/dt Where $\phi$ is magnetic flux. Why is it that if from $t_1$ to $t_2$ the coil makes a complete turn and during this turn the normal vector's angle with ...
3
votes
1answer
53 views

Entangled spins in a uniform magnetic field

I have been trying to calculate the time derivative of the expectation value of the operator representing the spin components of a a singlet state (e.g. sigma(z)tau(z)). I formed the tensor product of ...
22
votes
3answers
4k views

Extra strong magnet which doesn't demagnetize credit cards. How does it work?

I've just bought this case for my mobile phone. It has three credit card slots, which isn't strange at all, but in combination with a strong magnet closure, it almost seems a bit stupid, because, who ...
1
vote
1answer
50 views

Current carrying wire to suspend in midair? [closed]

A straight current carrying wire is inserted in a region of space where a strong magnetic field is directed vertically downward. How can the wire be oriented so that it is suspended in midair by the ...
0
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0answers
96 views

Current through moving bar on rails with non-constant magnetic field

I am working on the problem pictured below and I cannot figure it out. I have been using the equation d[flux]/dt = -BLv and V = -d[flux]/dt. However, since the magnetic field is not constant through ...
0
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0answers
58 views

How does mass of magnet with current-flowing wire inside change?

We just did an experiment where we put a coil inside of a magnet and let certain current run through the coil and measure the mass change of the magnet. I have looked/researched in textbook and ...
0
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2answers
262 views

Magnetic flux density of a solenoidal electromagnet

I am designing an electromagnet which will be used to test magnetic sensors. So I used to formula found at hyperphysics which relates the magnetic field flux density to the number of turns, the ...
4
votes
3answers
572 views

How to find the direction of an eddy current?

Suppose there is a magnetic field going from left to right. Suppose a thin sheet of metal conductor (e.g. a 1m*1m square) is dropped through the magnetic field such that the plane of the conductor is ...
4
votes
5answers
727 views

In what case does a Coil with Current flowing through it NOT produce a Magnetic Field?

According to what I've studied, when Current flows through a Coil, a Magnetic field is produced. Recently, I've been told that there is a case in which Current flows through a Coil Without producing ...
0
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1answer
50 views

Is there an intuitive explanation for the direction of the B field around a wire?

A wire has cylindrical symmetry, therefore we should consider the possibility of the induced by field in the p,phi and z directions. I know from the right hand rule that we only get a field in the phi ...
1
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1answer
41 views

Will my data drives be safe in an emp event? [closed]

If there was an emp event (maybe because the rotation of magnetism of the earth or an atomic bomb) would the data on my hard drives, ssd, dvd, mini dvi tapes and cassette tapes be safe?
0
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1answer
54 views

Electric and magnetic fields with synchrotrons

Can anyone describe to me one change to the electric field and one change to the magnetic field that MUST take place as particles gains energy in a synchrotron accelerator? This could also just be an ...
2
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0answers
39 views

Landau levels in ferromagnets

Consider a spontaneously magnetised (uniformly) conducting ferromagnet. Now suppose that there is no external magnetic field. The question is as follows: will the motion of electrons be quantized via ...
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1answer
30 views

Why is $\theta$$ = $$\theta$$_{2}$ and not Phi in this Magnetic Field due to Current in Loop Equation [closed]

I'm wondering how we know that $\theta$ = $\theta$$_{2}$ (essential to solving the problem) and that it is not equal to, for example, ϕ?
1
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1answer
289 views

$\pi$, $\sigma$ - atomic transitions with respect to the magnetic field axis

I am confused about the atomic transition with different polarized lights. I post the pictures as follows. There are four cases. In case 1, the right-handed circular polarized light ...
1
vote
1answer
127 views

Will a small magnet affect an insulated computer wire?

I'm designing something that involves a small magnet, probably about 0.5m in diameter, which will rest next to a computer wire carrying data, video, audio, etc. If the wire is insulated (think USB or ...
0
votes
0answers
36 views

Can measurement of Spontaneous Magnetization and susceptibility lead one to deduce the magnetic structure of a magnetic compound?

For a given magnetic compound, spontaneous magnetization and susceptibility are measured at various temperatures (in this paper). (SMS measurement) From neutron diffraction data the compound is found ...
0
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1answer
41 views

Does an infinite solenoid have constant magnetic field along its length?

So I'm aware of the fact that an infinitely long solenoid has radially uniform(constant) magnetic field inside. But does the magnetic field vary as one moves along its length? Reading the solenoid ...
3
votes
2answers
267 views

How strong would the Earth's “magnet” be if it was the size of a fridge magnet?

If you shrunk the "magnetic part" from inside the Earth down to a fridge magnet size, how strong would it be in Gauss? This is not a home work question. I just watched this video which included the ...
2
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0answers
26 views

Formation of vortices in superconductors

So I'm trying to understand how mixed state of a type II superconductor becomes the energetically favourable state. I've been through a simple approximate calculation considering a S-N boundary to ...
0
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1answer
64 views

Can an electric field help generate a current?

What i know or am guessing:- A moving/changing magnetic field creates an electric field. So if we take a rotating magnet near a coil of copper wire, it will induce a current right. So it means an ...
0
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1answer
49 views

The origin of Gauss' law for magnetism [closed]

What is the physical axiom leading us to the Gauss' law for magnetism?
0
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0answers
44 views

What physical properties affect magnetic attraction between a magnet and a surface?

What physical properties of a metal affect how strongly a given permanent magnet will be attracted to the metal? How do these properties relate to real-world materials that can be purchased either as ...
0
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1answer
57 views

Finding the limit for $\theta$

To find out the magnetic field for infinite wire, we can have an equation $$B= \frac{\mu_0 I}{4\pi s}(\sin\theta_2 - \sin\theta_1) $$ But how the limit of theta could be $\theta_1 = -\pi/2$ ...
0
votes
1answer
50 views

What is an awkward constant and is there a relation to ad-hoc hypotheses?

[I'm not entirely sure whether this is the right board, since it is not a technical but a soft question]. I'm reading the textbook "Spin Dynamics - Basics of Nuclear Magnetic Resonance", 2nd ed., ...
0
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1answer
37 views

Why is $\ell$ in $\mathbf F = I~\ell \times \mathbf B$ taken as shortest distance?

The equation $\mathbf F = I~\ell \times \mathbf B$ works good for a straight wire. But in cases where the wire is bent in the form of a sine curve or in a circle and the magnetic field is assumed ...
0
votes
1answer
38 views

How does one magnetic field effect another

Do the fields cancel or are they additive or something else. Can we direct and focus them and or amplify then with similar fields? Can we eliminate the electric portion of an electromagnetic field?
1
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2answers
42 views

Shorting a Superconducting Coil with A/C

When a superconducting coil carrying a direct current is shorted, it continues to carry the current without loss (approximately), assuming it stays cooled and superconducting. What would happen if ...
0
votes
1answer
17 views

Attracting atmospheric positive ions to carbon nano tubes for collection

Can nano magnets built into carbon nano tubes be used to attract moving positive ions from atmosphere to increase the resultant positively charged collecting mass?
1
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2answers
387 views

Does a changing magnetic field impart a force on a stationary charged particle?

Does a collapsing and re-establishing magnetic field impart a force on a stationary charged particle ? Does the charge particle get repelled and or attracted ? Does it move or spin ?
0
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1answer
98 views

Can a magnetic or electric field deflect subatomic particles?

I always wondered if the subatomic particles can be deflected by a magnetic or electric field. Basically I am asking the viability of the typical "Force Field" in movies.
0
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0answers
28 views

Induced emf around plane wing tips- varying magnetic field(revised)

I understand that a solenoid wire with an induced magnetic field can be subjected to a varying magnetic field. My question is if you can you have a varying magnetic field around the wing tips of an ...
3
votes
3answers
127 views

Why not a magnetic field local maximum?

Reading a brief on magnetic traps I've read that you can't have a magnetic field local maximum. I believe this is linked to the divergence of B being 0 in vacuum, but I don't see why one can have a ...
0
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1answer
40 views

Is there a current in this situation?

If a wire moves through a magnetic field a current is induced in the wire. If you drop a piece of wire through a magnetic field, the wire is of a finite length and the whole length is shorter than ...
1
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0answers
98 views

interaction of permanet magnetic field with electromagnetic field

I am working on non contact breaking system for a rotating permanent magnet in an electromagnetic field.so I would like to know if the interaction between the magnetic field and an electromagnet will ...
1
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1answer
130 views

Probability current for electron in uniform magnetic field: wave function forever splitting apart?

In this document http://hitoshi.berkeley.edu/221a/landau.pdf on Landau levels, in section 4, page 19, "Transitionally invariant Gauge", they analyze the free electron in a uniform magnetic field ...
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0answers
20 views

What's the relation to calculate the magnetic field away from a magnet?

The relation to calculate the magnetic field generated in a point P in front of a solenoid is : $$ B= N \frac {\mu_0 I} {2a} sin^3(\alpha) $$ with the values' meanings shown in the image. Now what ...