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
507 views

Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
5
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1answer
678 views

Peierls substitution vs minimal coupling

In the presence of vector potential (let's assume it's uniform), a tight-binding Hamiltonian will be changed according to the Peierls substitution: $$t_{ij}c_i^{\dagger}c_j \to t_{ij}e^{iqA|i-j|}...
25
votes
3answers
951 views

Do intergalactic magnetic fields imply an Open Universe?

According to a paper on the arXiv (now published in Phys Rev D), they do. How credible is this result? The abstract says: The detection of magnetic fields at high redshifts, and in empty ...
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2answers
45 views

Moving of spin up and spin down electrons in a magnetic field

Suppose we have an electron in a conducting space, and now we apply a magnetic field. Now according to the right hand rule, the electron will have a circular motion in the plane perpendicular to the ...
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2answers
753 views

How does the magnetic field get induced in car's tire?

I was amazed to see how my car's tire started attracting the nuts and bolts, how in the world did it induce the magnetic field? Never heard of such phenomena!!!
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1answer
31 views

How can a sinusoid be a steady current? [duplicate]

As far as I understand it, a steady/stationary/constant current is defined to have $dJ/dt=0$ (i.e., no explicit time dependence). So I would say that sinusoids cannot produce steady currents, yet ...
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0answers
25 views

What difference does it make if the turns in a tesla coil overlap?

Would a tesla coil in which the primary coil is made by overlapping the turns of the wire work?
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0answers
13 views

Lorentz force on a current carrying wire in a non-uniform magnetic field? [on hold]

If a current carrying wire is placed in a non-uniform magnetic field, how will this equation change: $$ F = IL \times B$$ I know I must integrate, but not sure if it's $F$ or $B$. Consider this ...
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1answer
42 views

Quantum state after change of magnetic field

I have the following conditions: $\lvert\psi(0)\rangle=\lvert+\rangle_x=\frac{1}{\sqrt{2}}\lvert+\rangle+\frac{1}{\sqrt{2}}\lvert-\rangle$. So the state at $t=T$ is $\lvert\psi(t)\rangle=\frac{1}{\...
2
votes
1answer
127 views

How force get transmitted when a magnet attracts iron?

According to particle physics , every fundamental force has its force carrier particle. Photon is a force carrier particle of electromagnetic force but how does force gets transmitted when a iron is ...
12
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3answers
5k views

Is it possible to kill a human with a powerful magnet?

I'm asking in terms of physics. Can powerful magnetic induction rearrange spins of my body in such way I will die? How? Or maybe it can rip all iron from me, which would make my blood cells useless? ...
4
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5answers
22k views

magnetic field outside a solenoid

I couldn't picture the idea behind the zero magnetic flux outside the solenoid properly.My teacher explained it as"Components of the magnetic field in other directions are cancelled by opposing fields ...
4
votes
1answer
42 views

Why do the magnetic poles of the Earth get reversed?

It has been confirmed that the magnetic poles of the Earth get reversed , but why should they get reversed in the first place ? Also, why is their pattern of reversal so arbitrary ? Geomagnetic ...
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vote
1answer
924 views

Forces on a wire moving in a magnetic field?

When a wire is placed inside a magnetic field and current starts to flow in that wire, that wire experiences the Lorentz force = $IL \times B$ and beings to move. Aside from induced motional - $\...
0
votes
0answers
23 views

Why soft iron 'plates' are used to hold the bar magnet pairs that are available in shops? [on hold]

I know that retentivity and coercive force for hysteresis are smaller for soft iron, than steel. But still, only soft irons are found to be stuck together with the pair of bar magnets when unboxed. ...
0
votes
2answers
372 views

Magnet dimensions for 3-phase permanent generator

I'm making a 3-phase permenant generator. According to Faraday's law, the emf produced is negative number of turns times the change in magnetic flux over the change in time. If it is only the CHANGE ...
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2answers
55 views

Energy of electric field and magnetic field

I am studying about inductors and capacitors. They store their energy in the form of electric field and magnetic field.Energy is required to create fields.But if we take an isolated charge and nothing ...
6
votes
3answers
639 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 ...
0
votes
1answer
33 views

How to create a strong magnetic field using permanent magnets

I would like to build a strong magnet using 100 6"x4"x1" permanent magnet blocks. What is the best way to place them so I get the strongest magnetic field? (Should I stack 2 row of 50 blocks and put ...
0
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0answers
28 views

Magnetic field due to a SQUARE loop at a point on the axis? [closed]

A square loop of side $a = 6\,cm$ carries a current of $1\,A$. Find the magnetic field in a point at a height of $\sqrt{7}\,cm$ from the center of the square (thus lying on the axis of the square). ...
1
vote
1answer
190 views

What is blocking the magnetic field of this neodymium magnet?

I opened up my hard drive and pulled out (among other things) the top and bottom braces for the reading arm. Each bracket contains a really powerful neodymium affixed to its underside. When the ...
1
vote
1answer
350 views

Calculating the magnetic field from rectangular conductor

I want to apply the Biot-Savart law to calculate the magnetic field at a point created by current flowing through a square/rectangular conductor. More specifically, a trace on a printed circuit board. ...
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0answers
16 views

how to calculate the magnetic force between a permanent magnet and a magnetic field?

Can anyone provide me with the equation of magnetic force between the permanent magnet and a magnetic field? Also kindly attach the reference journal link. Thanks in advance.
4
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1answer
340 views

Boundary conditions on current carrying wire

I'm trying to simulate by finite elements method Maxwell equations for a current carrying wire. My 3d geometry consists of a cylinder and a box containing it. I will use a mixed formulation and ...
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3answers
178 views

Why do magnetic field lines converge where the strength is strongest?

In most of the sites, they just say that "to determine the strength of the magnetic field, one must look at how many lines are present at a particular location." But my question is why? Why is this ...
2
votes
1answer
34 views

Relationship Between Magnetic Dipole Moment and Spin Angular Momentum

I am reading Introduction to Quantum Mechanics 1st edition by David J. Griffiths and I have a couple questions about this section on page 160. A spinning charged particle constitutes a magnetic ...
0
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1answer
209 views

What is the magnetic flux density “outside” the solenoid when AC current is passing through it?

I know that there are well defined equations explaining the magnetic flux density in the solenoid. However what about magnetic field outside the solenoid? How is the magnetic flux density related ...
2
votes
3answers
112 views

Why can the divergence of vector potential be anything?

Purcell in his book was deriving the vector potential $\bf A$ using $\text{curl}\;(\text{curl}\; \mathbf A)= \mu_0 \mathbf J\; .$ After some algebra, he came to this: $$-\frac{\partial^2 A_x}{\...
0
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1answer
40 views

Why metal sphere (conductor) is used in Van de graff as the output terminal, not any other material , specifically any insulator?

Why metal sphere (conductor) is used in Van De Graff as the output terminal, not any other material, specifically any insulator?
0
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1answer
5k views

How can a magnet have a greater magnetic field strength than a bigger, heavier and more powerful magnet made of the exact same material?

Here are some informations I found on the magnetic field strength (also called "magnetic flux density" or "magnetic induction", commonly denoted as B and expressed in tesla or in gauss) of an average ...
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0answers
30 views

Why don't we see a precession of compass in constant magnetic field?

It is known that spin particles put in magnetic field precess at the Larmor frequency around the axis of magnetic induction B. For example if the spin was perpendicular to B, the spin of the particle ...
0
votes
1answer
34 views

Why does the primary coil get very warm with DC supply but not with ac supply?

It's about an investigation carried out on the transformer effect . The primary coil of 20 turns and the secondary coil of 50 turns is wound around a laminated iron core.
2
votes
3answers
107 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 ...
0
votes
1answer
775 views

Magnetic fields in transformers and back emf?

i am having some trouble with understanding the magnetic fields inside transformers and how they relate to back emf. My first query is: is the magnetic field produced inside the soft iron core ...
2
votes
1answer
42 views

Problem with magnetic field due to relative motion

We know that, moving charge produces magnetic field in the surrounding space. Consider this scenario : A charge 'q' is moving with a constant speed 'v' in the direction of positive x axis of a ...
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1answer
26 views

Do Magnetic Solids exhibit their Magnetic properties in their Gaseous state?

Example Does cobalt, a solid exhibit Magnetic properties when converted to its Gaseous State.
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1answer
108 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 ...
1
vote
1answer
26 views

'Printing' magnetic polarity into a material

There is a company out there that 'prints' magnetic pixels, a.k.a. maxels, into a material. In doing so, they're able to choose the distance of effect of magnetic fields they create, independently of ...
2
votes
1answer
174 views

Magnetic field line distribution

If I had a magnetic bar in space that was 2cm wide and 2cm high and was one Earth diameter long and had the same magnetic strength as the Earth, would the distribution of field lines be the same ...
0
votes
2answers
298 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 ...
0
votes
1answer
43 views

Does a precessing spin in constant magnetic field change the field somehow?

If an electron enters a magnetic field along the lines of the magnetic induction it spin starts to preccess. Suppose the field was made by a coil (toroid). What changes happen in the field - current - ...
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2answers
689 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 ...
0
votes
1answer
39 views

Gruchestein Effect?

I overheard that name in a conversation, but not very clearly. I can't find anything on Google, probably because of my spelling is completely wrong. Does anybody knows about an effect with a similar ...
1
vote
1answer
28 views

differences of Aurora Borealis (North) vs. Aurora Australis (South)

I was wondering about the differences between the Northern vs. Southern lights: will one pole collect the positive charges, and the other the negatives? I know that the solar wind is composed mainly ...
1
vote
1answer
276 views

Explanation of force amplification inside a solenoid

For a system being actuated by a motor, the force can be amplified by gearing. The energy is being used for force instead of distance, so it produces more torque but moves slower. For a system being ...
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0answers
16 views

How does the velocity of a magnet falling through a solenoid affect the induced voltage?

Given Faraday's Law, $\mathcal{E}=-N \frac{\partial \phi}{\partial t}$, we can induce an EMF by dropping a magnet through a coil of wire. How would the velocity of this magnet relate to the induced ...
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0answers
29 views

Solving Bloch equation for MRI

I am trying to write a numerical solver for Bloch equation to track the magnetisation of a spin during the excitation and relaxation processes. The general Bloch equations can be written as: $$ \...
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3answers
33 views

How to determine the concentration and sign of the charge carriers in copper

I need to design a procedure for an experiment to determine the concentration and sign of the charge carriers in copper. I'm given: A slab of copper 2.0 mm thick, 1.5 cm wide, and 4 cm long One very ...
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2answers
169 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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vote
1answer
29 views

Verify Faraday's law of induction [closed]

I need to design a procedure for an experiment to verify Faraday's law of induction. I'm given: A Helmholtz coil of radius 15 cm Three plastic spheres of radii 1 cm, 1.5 cm, and 2 cm. A spool of ...