Questions tagged [magnetic-fields]
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 [magnetism] tag, as questions about the phenomenon & theory of magnetism do not necessarily involve the discussion of fields.
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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 a magnetic field 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 ...
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If you are vacuuming your carpet and you wrap the cord around your body do you become a magnet?
If you wrap an active electric cord around your body, do you become an electromagnet?
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What is the difference between the magnetic $H$-field and $B$-field?
From Wikipedia:
"The term (Magnetic Field) is used for two distinct but closely related fields denoted by the symbols $B$ and $H$, where $H$ is measured in units of amperes per meter in the SI. $...
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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-...
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If magnetic field lines don't exist, what are these iron filings doing around a magnet?
Obviously the iron filings can be seen aligning themselves along the virtual magnetic field lines produced by the permanent magnet, the virtual magnetic field line is made of electromagnetic field due ...
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Is there an underlying physical reason why the Coriolis force is similar to the magnetic component of the Lorentz force?
I couldn't help but notice that the expression for the magnetic component of the Lorentz force,
$$\mathbf F = q\,\mathbf v \times \mathbf B\,,$$
is very similar in its mathematical form to the ...
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Why doesn't light affect a compass?
In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
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Is there an intuitive explanation for why Lorentz force is perpendicular to a particle's velocity and the magnetic field?
The Lorentz force on a charged particle is perpendicular to the particle's velocity and the magnetic field it's moving through. This is obvious from the equation:
$$ \mathbf{F} = q\mathbf{v} \times \...
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What is happening when magnetic field lines snap or break?
In discussions of sun spots and auroras on Earth, magnetic field lines are often described as "snapping" or "breaking", with the result of releasing charged particles very ...
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Why is there no magnetic field around a wire connected to electricity at home?
Is it true that an electric current that flows through a conductor creates a magnetic field around the conductor?
If yes, then why doesn't the magnetic sensor of my mobile device react in any way to ...
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How are magnets held together, and why do they not explode?
Imagine we have a magnet (red side is the north pole, blue side is the south pole), and imagine two ways to split it.
The first way:
When we split it by separating the north pole from the south pole, ...
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Is the presence of a magnetic field frame-dependent?
I do not have a strong background in physics, so please refrain from using complex mathematics in any answers :)
I was on
this site, and I read:
When an electrical charge is moving or an ...
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Can someone please explain magnetic vs electric fields?
I've looked through about 20 different explanations, from the most basic to the most complex, and yet I still don't understand this basic concept. Perhaps someone can help me.
I don't understand the ...
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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 ...
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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 ...
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Does special relativity make magnetic fields irrelevant?
I've heard that special relativity makes the concept of magnetic fields irrelevant, replacing them with relativistic effects between charges moving in different velocity frames. Is this true? If so, ...
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Why is Earth's climate so stable?
Earth wasn't always the only water-world in the solar system. Mars also appear to have started out wet
but, as conditions changed, Mars lost its oceans.
So, how has Earth managed to avoid a similar ...
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Is there just one EM field for the whole universe?
Does our universe contain individual magnetic fields ?
For example two different magnets, one here on earth and one on mars. Do both of them have their own magnetic field? Or is there only one single ...
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Why does the Earth even have a magnetic field? [closed]
From my knowledge of magnetism, if a magnet is heated to a certain temperature, it loses its ability to generate a magnetic field. If this is indeed the case, then why does the Earth's core, which is ...
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Why don't we define potential due to a magnetic field?
We define electric potential and gravitational potential and use them quite often to solve problems and explain stuff. But I have never encountered magnetic potential, neither during my study (I am a ...
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What is the magnetic flux through a trefoil knot?
Imagine a closed loop in the shape of a trefoil knot (https://en.wikipedia.org/wiki/Trefoil_knot). How should one calculate the flux through this loop? Normally we define an arbitrary smooth surface, ...
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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 (...
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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 ...
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Why is there no gravitational magnetic field? (Or, is there?)
We can think that the electric field and the gravitational field operate similarly in the sense that the forms of their governing laws (namely, Coulomb's law and Newton's law respectively) are ...
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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 ...
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Why are the number of magnetic field lines finite in a particular area?
One can draw/imagine as many unique (curved/straight) lines as he/she wants in some specified finite area (assuming that each line is unique if it doesn't overlap with another line). Then how can the ...
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Why is Ampère's law violated if there are no fringe fields?
What's wrong with the following diagram?
Image source: Page 183, NCERT Physics Textbook for Class XII Part I
The reason stated in my textbook is as follows:
Magnetic field lines between two pole ...
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Is there a more "physically mature" way to think about the right hand rule with electromagnetism?
I've always found using the righthand rule to remember how forces, B-fields, and particle velocities to be intellectually cheating myself a bit. It feels like being able to multiply numbers by using ...
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Why are magnetic field lines imaginary?
There are many sources online which say that magnetic field lines are imaginary such as Toppr, Vedantu and CBSE Academic.
I do know that magnetic fields are real and do exist. But when can we see ...
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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 ...
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How specifically does an MRI machine build an image from received radio waves?
Unlike the excellent Wikipedia page on ultrasound imaging, the one on MRI only explains the principle theory behind MRI - that oscillating strong magnetic fields cause water molecules to emit ...
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Why are real photons so much less efficient in carrying momentum than virtual photons?
When two like magnetic poles are brought together, there's a repulsive force felt that's inversely proportional to their separation. In the standard model, the answer to "What is transmitting ...
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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 ...
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What force particle mediates electric fields and magnetic fields?
The force carrier for magnetic fields and electric fields are supposedly photons. I don't get it:
1) Wouldn't that mean that a charged particle (e.g. an electron or even a polarized H2O molecule) ...
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Can a magnetic field exist without an electric field present?
I know an electric field can exist without a magnetic field as in the case where you have a stationary point charge.
But, magnetic fields are created by moving charges so wouldn't you always need an ...
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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, ...
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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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Why do we tap on cardboard to see magnetic field lines?
If we sprinkle iron particles on a cardboard where a bag magnet is kept and tap the board gently then the particles get arranged in a way that they look like field lines. But I am confused why do we ...
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Would a compass with unmagnetized needle work?
We know that the needle that is used in a compass is a permanently magnetized ferromagnetic material and commonly steel is used.
If we used an unmagnetized iron needle instead, would it still align ...
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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 ...
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Magnetic field changes induced by vibrating electric guitar string
Here is a picture (from a paper by Feinberg and Yang in the Journal of the Acoustical Society of America) of an electric guitar string vibrating (mostly in the $y$ dimension) near a permanent magnet.
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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 ...
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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 ...
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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 ...
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Electromagnetic fields vs electromagnetic radiation
As I understand, light is what is more generally called "electromagnetic radiation", right?
The energy radiated by a star, by an antenna, by a light bulb, by your cell phone, etc.. are all the same ...
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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 ...
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Must magnetic field lines close upon themselves or go to infinity?
Conventional wisdom tells us that magnetic field lines must either form closed loops, or shoot off to infinity. However, this leaves out the possibility that a magnetic field line, even if it stays ...
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Why iron filings sprinkled near a bar magnet aggregate into separated chunks?
When iron filings are sprinkled near a bar magnet, they reveal the "shape" of the magnetic field.
(source)
But why do the (needle-shaped?) filings aggregate into chunks with empty space between them ...
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Why are magnetic fields a consequence of special relativity? [duplicate]
I'm very confused about why it is a consequence of special relativity.
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Can we stop moving bullets by Eddy currents? [closed]
My idea is to make a gun-like model which would be the source of a changing magnetic field so that Eddy currents are produced in the bullet. Would it be enough to stop a moving bullet? I'm posting a ...
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