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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41
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8answers
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How can Magnets be used to pick up pieces of metal when the force from a magnetic field does no work?

I learned that the force from magnetic fields does no work. However I was wondering how magnets can be used to pick up pieces of metal like small paperclips and stuff. I also was wondering how magnets ...
17
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4answers
2k views

What is the magnetic field inside hollow ball of magnets?

Setup: we have a large number of thin magnets shaped such that we can place them side by side and eventually form a hollow ball. The ball we construct will have the north poles of all of the magnets ...
24
votes
5answers
4k views

Does a magnetic field do work on an intrinsic magnetic dipole?

When you release a magnetic dipole in a nonuniform magnetic field, it will accelerate. I understand that for current loops (and other such macroscopic objects) the magnetic moment comes from moving ...
10
votes
2answers
14k views

Effects of a very large magnetic field on the human body

Ever since reading about the NHMFL I have always wondered about this and asked several people without getting a good satisfactory answer. My question is, considering the simplest case let's say a ...
1
vote
1answer
284 views

How does a magnet work?

I'm having trouble understanding how a magnet (not the field that is generated as a result but the material itself) work. The particles are aligned in a specific direction to give rise to force but I ...
11
votes
2answers
2k views

Is Biot-Savart law obtained empirically or can it be derived?

Well, there's already a question like this here so that my question could be considered duplicate, but I'll try to make my point clear. Is there a way to derive Biot-Savart law from the Lorentz' Force ...
9
votes
2answers
2k views

What prevents this magnetic perpetuum mobile from working?

As a child, I imagined this device, which may seem to rotate indefinitely. I have two questions. Is this perpetual motion machine already known? If it is, could you please give some references? What ...
8
votes
4answers
3k views

How do permanent magnets manage to focus field on one side?

The actuator of a hard drive head consists of two very strong neodymium magnets, with an electromagnetic coil between them. If you take that apart, the magnets attract each other very strongly. ...
7
votes
2answers
653 views

Mechanism by which electric and magnetic fields interrelate

I read that force due to electric field on some particle in one reference frame can exhibit itself as force due to magnetic field in some other reference frame and that electric and magnetic fields ...
5
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2answers
714 views

Magnetic field lines

When I searched the net about magnetic field lines, Wikipedia told something about contour lines and that magnetic materials placed along a magnetic field has some specific loci, which i did not ...
8
votes
2answers
238 views

What is the mechanism by which magnetic fields do work?

I've seen some conflicted answers to this question in texts and on the web, in the case of a dipole, for example. Do magnetic fields do work directly, or is it their induced electric fields that do ...
11
votes
2answers
343 views

How are the northern lights produced?

Although I've never seen it myself, I hear the northern lights are a sight to be seen! I know they're related to the Earth's magnetic field but I don't know much more about them. What is the physical ...
1
vote
2answers
370 views

Is it possible to detect fake Tungsten aka Wolfram gold bars with a strong magnet?

Tungsten aka Wolfram is paramagnetic so it is weakly attracted to magnets. A guy devised the following to test for Tungsten in gold bars: http://www.youtube.com/watch?v=foELQ7T8_90 But he is using ...
1
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3answers
2k views

Magnitude of magnetic field at the center of circular wire

I'm preparing for an exam by solving the sample questions , here is the one I'm having difficulty with : Following is the given circuit. Which contains two resistance $R_1$ and $R_2$ in form of ...
0
votes
1answer
120 views

What are magnetic field lines?

Does a magnetic field have concentrations of magnetic force lines as seen when putting iron filings over top a bar magnet or are these imaginary? I.e. are they just an artifact of the iron being a ...
8
votes
1answer
258 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? ...
16
votes
5answers
904 views

Does a magnetically suspended frog feel weightless?

Magnetic levitation has been used to suspend frogs in midair. I was wondering: Does the animal still feel gravitational pull? I mean: Does the frog feel like an astronaut on the ISS, or does he feel ...
10
votes
6answers
7k views

What are the fields produced around a current carrying conductor?

If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged ...
8
votes
2answers
5k views

What is the difference between an electric and a magnetic field? [closed]

This question is a consequence of another question of mine which is about spin. Here is my spin question. What is the difference between these two fields? How do they occur? Am I right if I say that ...
5
votes
4answers
189 views

Do magnets redshift light?

Do magnets redshift light? Suppose we have an extremely powerful magnet (say the size of the Sun) and we have a smaller paramagnetic material above it (say. Titanium Brick which is ...
3
votes
0answers
208 views

Finding the terminal velocity of a magnet dropped in a solenoid

We have to find proportionality of the terminal velocity with the factors of the system: Plot: a small dipole(mass $m$) with dipole moment $\mu$ is dropped in a long solenoid (radius $r$, ...
2
votes
2answers
104 views

Aharonov-Bohm Effect electricity generation

This question is based on highly intuitive picture of the Aharonov-Bohm effect (perhaps a naive one). From what I have read, the current explanation of the AB effect is that although the electron ...
2
votes
2answers
96 views

What can be measured or derived about a remote magnetic field? [closed]

This question related to Why are magnetic lines of force invisible? and is motivated by a comment of @BlackbodyBlacklight, based on that, the illustrating example may depend on that linked question as ...
2
votes
1answer
1k views

Force between two bar magnets

I need to know how to calculate force between two bar magnets. I searched and found an answer on Wikipedia, but I don't really trust Wikipedia, a lot of crazy stuff is posted there. So I searched ...
2
votes
3answers
5k 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 ...
2
votes
2answers
110 views

Would a magnetic rod through Mars shield it from solar wind?

Would a magnetic rod going all the way through Mars shield it from solar wind?
1
vote
1answer
112 views

Does two Neodymium magnets stick together twice the power?

Assume I use a coil to create B-flux and put ONE Neodymium cylinder magnet (1"diameter & 0.25" thick) close to the flux, it would create 10 lbs force. Does it mean that I put TWO cylinder magnets ...
1
vote
1answer
329 views

Why is the Maxwell Stress Tensor symmetric?

What is the physical meaning of the Maxwell Stress tensor symmetry?
5
votes
1answer
205 views

Why Inox Steel doesn't interact with magnets?

My dad has a HUGE magnet on his workshop. I love magnets, and when I saw it, I asked him what it was for. His reply was: "I don't know why, but inox steel bolts don't get attracted to it, so I use ...
4
votes
2answers
705 views

Cancel out Earth's Magnetic field

Is there any tools except helmholtz coil to cancel out earth's magnetic field to calibrate magnetometers in practice.
3
votes
1answer
77 views

How is earth a magnet while it's volume is mostly above curie temperature?

I was assuming the earth's magnetism is similar to a permanent magnet; But below a depth of somewhere near the Mohorovičić discontinuity (Moho) between earth's crust and mantle it should be above ...
3
votes
2answers
1k views

Does changing the electric / magnetic field cause self-reinforcing induction of the other?

I understand that changing electric field produces magnetic field and changing magnetic field produces electric field. Are these produced magnetic and electric field produced due to one defined to be ...
2
votes
1answer
86 views

Motional EMF and EMF?

What is the difference between motional EMF = $-vBL$ , and Faraday's law of induction $\displaystyle\mathcal{E} = \left|\frac{d\Phi_B}{dt}\right|$? Aren't they the same? What is the relation of ...
2
votes
0answers
817 views

How to calculate magnetic pole strength?

I have 2 magnets. I need to know the force between them. In a previous Phys.SE question, conclusion was: we need to use a dipole-dipole interaction equation, which included m, which the magnetic ...
2
votes
1answer
392 views

Hamiltonian matrix off diagonal elements?

I'm trying to understand how Hamiltonian matrices are built for optical applications. In the excerpts below, from the book "Optically polarized atoms: understanding light-atom interaction", what I ...
2
votes
3answers
178 views

Is there energy stored when iron is magnetized?

When a piece of iron is magnetized, and the domains are aligned, Is there energy stored? If so, how much energy is stored? If there is an attraction between that same iron and the source of the ...
2
votes
1answer
400 views

Can I Demagnetize a ferromagnet with a hammer?

If an iron is exposed to an external magnetic field, the iron's domains are all aligned with that ext-B . If I strike it with a hammer, will it be demagnetized? Comparing it with heat, I know the Tc ...
2
votes
1answer
1k views

Magnetic Fields created by Current-Carrying Wires

The drawing shows two perpendicular, long, straight wires, both of which lie in the plane of the paper. The current in each of the wires is I = 5.6 A. What is the force and torque acting on each wire ...
1
vote
1answer
78 views

Why is the geomagnetic north pole at a different location from the magnetic north pole?

According to this site Magnetic North, Geomagnetic and Magnetic Poles The Geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet hypothetically ...
1
vote
1answer
132 views

Saturation of an iron core?

Lets assume we have a 1 kg iron core, and a 100 kg iron core. Now saturation is defined as how much that core can absorb the magnetic field, since they are different sizes, don't they saturate at ...
1
vote
2answers
496 views

Manganese has more unpaired electrons than Iron so why is Iron ferromagnetic Manganese paramagnetic?

Manganese has five unpaired electrons, but Iron has four, then why is Iron ferromagnetic and Manganese paramagnetic? What's that property I'm missing?
1
vote
1answer
124 views

Why can coercivity be used in place of magnetization when modelling permanent magnets?

I'm trying to understand how permanent magnets can be modeled in finite element methods. FEMM's manual, here, states that it treats a PM as a solenoid with the same surface current as the PM, and then ...
1
vote
4answers
3k views

North and south of magnetic field

The current I is flowing upward in the wire in this figure. The direction of the magnetic filed due to the current can be determined by the right hand rule. Can we determine the north and the south ...
1
vote
2answers
2k views

Magnetic poles in Halbach array?

I am a bit confused by the description of Halbach arrays. It is said that the line of magnets aligned in certain way results in cancellation of magnetic field on one side of the array, and ...
0
votes
2answers
95 views

Does a permanent magnet loose its magnetism?

The question is slightly deceiving however still simple for those academics therefore, here I present my question: If I take a para-magnetic material and put it very close to a homogeneous magnetic ...
0
votes
1answer
97 views

Magnetic Shielding?

Can magnetic fields be "blocked"? For example, in the game, TitanFall, a robot stop bullets with ( presumably ) a magnetic shield. I wish to calculate the magnetic force required to stop a bullet ...
0
votes
1answer
293 views

Magnetic field of a solenoid at the poles?

It's known that at the center of an electromagnet/solenoid the magnetic field $B$ is strongest there. At the pole/edge of the solenoid/ or electromagnet is the magnetic field $B$ strong? Let's assume ...
0
votes
0answers
63 views

Lasers can demagnetize ferromagnets?

How is it possible to demagnetize a magnet with a laser? Source: http://www.helmholtz-berlin.de/pubbin/news_seite?nid=13657&sprache=en&typoid And the paper: ...
0
votes
1answer
65 views

Why do some of the iron fillings arrange in a particular pattern when sprinkled around a magnet, instead of getting attached to the magnet?

My sir started a new chapter "magnetism and matter". Sir said that iron fillings form a particular arrangement when sprinkled around a magnet. I saw the figure in my book where it was shown the ...
0
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3answers
1k views

What is the use of this formula 1 Tesla = 1 Newton/Ampere/Meter?

What does Newtons/Ampere/Meter stand for? From this formula: 1 Tesla = 1 Newtons/Ampere/meter what can it be used for? To do what? Ampere/meter Is the same unit as a field's intensity H? Or what is ...