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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47
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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 ...
25
votes
6answers
6k 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 ...
12
votes
3answers
24k 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. ...
22
votes
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
votes
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 ...
17
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3answers
7k 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 ...
12
votes
2answers
39k 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 ...
2
votes
4answers
518 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 ...
14
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4answers
12k 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
14k 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 ...
13
votes
6answers
28k 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 ...
11
votes
2answers
6k 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
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4answers
5k 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. ...
5
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2answers
2k 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
266 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
6k 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
684 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
744 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
2answers
4k 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?
0
votes
2answers
180 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
358 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 ...
8
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
659 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 ...
2
votes
3answers
208 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 ...
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.
23
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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 ...
7
votes
3answers
1k 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 ...
6
votes
1answer
615 views

How much power would be needed to make a substitute for natural Earth magnetic field?

Imagine the Earth's magnetic field will take a "maintainance pause" for 1000 years and there is gigant 10 years "doomsday countdown timer" ticking in the sky. The magnetic field will be just normal ...
4
votes
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 ...
4
votes
3answers
600 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 ...
12
votes
6answers
1k 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 ...
6
votes
7answers
4k views

Bar magnet dropped through coil

If you have drop a bar magnet through a coil so that it goes all the way through I was told the graph of emf induced in the coil vs time looks something like this: (emf induced is on y axis, time ...
4
votes
3answers
2k views

What will happen to a permanent magnet if we keep the same magnetic poles of two magnets close together for a long time?

What will happen to permanent magnet's magnetic field or magnetic ability if we keep same magnetic poles of two permanent magnet for long time? Will any magnetic loss happen over the long period of ...
4
votes
2answers
3k 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. ...
2
votes
2answers
61 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
1answer
306 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
2k 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)?
2
votes
2answers
184 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
1k views

Would two Neodymium magnets stick together with 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 of force. Does that mean that putting TWO cylinder ...
12
votes
2answers
381 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
1k 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
197 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
2k 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
5k 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
4answers
139 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 ...
2
votes
2answers
385 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 ...
2
votes
3answers
4k 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 ...
1
vote
2answers
31 views

Permanent Magnet Lines & Currents:

A permanent magnet produces lines of magnet flux that we call a "magnetic field". Those lines come from inside the magnet, come out of the N pole, loop outside the magnet, & return back into the ...
1
vote
2answers
189 views

Conducting rod moving through magnetic field

If a conducting rod moves through a magnetic field which way do its electrons move? In my revision guide it shows the following picture (more or less, but the following is my drawing of it -- I ...
1
vote
1answer
67 views

Is the electron's magnetic dipole moment influenced by the measurement method?

The electric charge of an electron at rest is a constant value and is not influenced by the measurement instrument. The measurement instrument by itself can give more or less accurate result, but does ...