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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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 ...
25
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6answers
7k 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 ...
24
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4answers
10k views

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

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 that this is a different question. Is there a way to derive Biot-...
22
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4answers
3k 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 ...
2
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1answer
1k 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 ...
1
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2answers
5k 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?
12
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3answers
26k views

How does Hendo hoverboards achieve the self-propelling motion? What is the MFA?

From what I understand of the idea behind Hendo hoverboards, they use four disc shaped hover-engines to generate a self-propelling motion. I also understand that it uses Lenz's law and eddy currents. ...
15
votes
2answers
44k 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 ...
14
votes
4answers
15k views

How long does a permanent magnet remain a magnet?

I have a bunch of magnets (one of those game-board thingies) given to me when I was a school-going lad over 20 years ago, and the magnets feel just as strong as it was the day it was given. As a ...
7
votes
3answers
15k views

Do magnets lose their magnetism?

I recently bought some buckyballs, considered to be the world's best selling desk toy. Essentially, they are little, spherical magnets that can form interesting shapes when a bunch of them are used ...
14
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6answers
32k views

Can magnetic fields be redirected and focused at one point?

I know that magnetic fields can be redirected, but... given a situation where you have static magnetic field over a large area, and you want to quickly change the magnetic field strength. Is it ...
2
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4answers
613 views

How any material can provide electrostatic and magnetic shielding

Several metallic objects like Iron, Copper etc can provide electrostatic shielding (one should remain inside the car during thunderstorm) and several superconductors like HTS (High Temperature ...
12
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4answers
2k views

Why should Conservative forces have their curl equal to zero?(intuition)

There are several conditions that must be met in order for a force to be conservative. One of them is that the curl of that force must be equal to zero? What is the physical intuition behind this? If ...
11
votes
2answers
7k 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 ...
10
votes
4answers
6k 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. There'...
6
votes
2answers
3k 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 ...
3
votes
1answer
372 views

Induced magnetic field produces electric field and vice versa forever!

So here are the two of Maxwell's laws that I am interested in: So we have the simple circuit (from google): So, before the system goes into steady-state we know that charge slowly accumulates on ...
15
votes
8answers
7k views

What is the electric field generated by a spinning magnet?

Consider a cylinder of permanently magnetized material, with uniform magnetization pointing along the cylindrical symmetry axis (the $z$-direction). The magnet is rotating about its cylindrical ...
8
votes
2answers
874 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 ...
3
votes
1answer
1k 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 ...
0
votes
2answers
243 views

Why do we multiply the magnetic flux by the winding number?

A current I flows through a solenoid (with n turns). Self inductance is $L$. If the magnetic flux is $\phi$, I am taught that $-n\phi=LI$ I dont understand the part with $n$, why do we have multiply ...
0
votes
1answer
387 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 ...
9
votes
2answers
1k 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 ...
4
votes
4answers
1k views

Can current be induced in a superconductor?

Moving a magnet close to a conductor induces a current. If it consists of a superconducting material with resistance $R=0$, then my textbook says: Then the induced current will continue to flow ...
4
votes
1answer
235 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 '...
4
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2answers
1k 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.
24
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5answers
2k views

Why do we deal only with large scale magnetic fields in astrophysics, and not electric fields?

In astrophysics there is a lot going on about strong, large scale magnetic fields: in stars (prominences), magnetic dynamos, compact accretors collimating jets, etc. There's even a special ...
4
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3answers
638 views

The magnetic field of a magnetic monopole

Let us define the magnetic field $$\vec{B} = g\frac{\vec{r}}{r^3}$$ for some constant $g$. How can we show that the divergence of this field correspond to the charge distribution of a single magnetic ...
4
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2answers
1k views

Which mathematical operation does the right hand rule for current come from?

I am currently wondering about this famous rule: Where does it come from mathematically that when you point with your thumb in the direction of the current, your curved fingers will point in the ...
2
votes
3answers
6k views

1 Tesla electromagnet?

Is it possible to create a powerful electromagnet at home? With use of a ferromagnet it seems so... Using the following formula: $B(Tesla)= k\mu_0nI$. I understand some ferromagnet's like iron could ...
1
vote
1answer
351 views

What is a magnetic field [closed]

What exactly is the magnetic field? I know what it does, but I want to know what it's made of at microscopic level, and how it gets its shape. By comparison with the electrostatic field, which is ...
16
votes
6answers
16k views

Where do magnets get the energy to repel?

If I separate two magnets whose opposite poles are facing, I am adding energy. If I let go of the magnets, then presumably the energy that I added is used to move the magnets together again. However, ...
12
votes
6answers
2k views

Are metals more heavy due to the Earth's magnetic field?

Non-metal objects are attracted to the Earth due to gravity. So the weight of non-metal objects can be only dependent on their mass. On the other hand metals can be attracted to the Earth's magnetic ...
5
votes
2answers
473 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}}...
4
votes
3answers
4k views

Why does an electric motor burn up when you physically stop it?

As an electric motor spins, the energy from the electricity is 'conducted' to the rotor by the magnetic fields. However, when the motor is stopped, the energy becomes heat and burns up to motor. ...
3
votes
3answers
481 views

Do moving charges get affected by the magnetic field they create while moving to constitute current? If not, how can self-induction be possible?

Let a bunch of charge move with a constant velocity $\mathbf v\;.$ Since, the charges are moving, they would create magnetic field $\bf B$ as it is current that produces magnetic field. Now, would $\...
2
votes
1answer
408 views

Force between two finite parallel current carrying wires

Remark: This is not a homework question...It is pure out of theoretical interest. I asked this the mathematics-community a couple days ago and got no answer, so I figured I'd try here. Most standard ...
2
votes
2answers
116 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 ...
2
votes
2answers
3k views

Why does Earth behave like Natural Bar Magnet?

What is the reason for the Earth to behave like a bar magnet and have poles (North and South poles)?
1
vote
1answer
111 views

What is the nature of the magnetic fields? [closed]

In this question, I am hoping to find out if there is an explanation to the magnetic hidden forces. In other words, what causes these fields? Is there any suggested theory, or any confirmed ones ? ...
1
vote
3answers
162 views

Why geologist do not consider molten iron in the magma to be the source of Earth's magnetic field?

This was a question that came in a exam. How come is this possible? Actually, a question on the source of Earth's magnetic field was asked here on physics SE, which matches my opinion. The ...
0
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5answers
108 views

How is the electromagnetic field made?

I know that an electric field is created by a particle with a charge and that a magnetic field is created by a moving charge but how do they combine to make a electromagnetic field?
0
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1answer
7k views

Work done by magnetic field [duplicate]

I know Lorentz force don't do any work. but I want to know whether any type of magnetic field do a work or not.
12
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2answers
384 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 ...
10
votes
1answer
2k views

Spikes on ferrofluid?

What exactly are the spikes, or peaks and valleys, caused by in pictures such as these Wikipedia states that "From the point of view of magnetic energy, peaks and valleys are energetically ...
10
votes
2answers
257 views

Does the geomagnetic field rotate?

The Earth rotates about it's own axis. Do the geomagnetic field lines rotate due to this rotation or not?
5
votes
1answer
3k views

Magnetic field insulators

I was wondering if there is any way to stop the magnetic field, without having the insulator turned into magnet. Let me present this as a simple case, there is a magnet to the left and a piece of iron ...
4
votes
2answers
6k 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 ...
3
votes
2answers
450 views

Must every magnetic configuration have a north and south pole?

Magnets have a magnetic north and south pole. Solenoids too have north and south pole from which magnetic fields comes out and goes in respectively. But is it that every magnetic configuration have a ...
3
votes
4answers
176 views

Positive work by a magnetic field

Consider a single charge moving only under the influence of Magnetic Field $\vec{B}$. The charged particle moves in a circle and the work done by $\vec{B}$ is 0. Now consider a current element in a ...