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
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Why do Magnetic North and South Poles never exist by themselves? [duplicate]

As the title suggest, whilst I was reading I saw written that a 'Magnetic North or South Pole has never been found by itself'. And I was wondering why this was?
0
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1answer
39 views

Are magnetic orbits possible?

I have a small ball with lots of magnets embedded in it with all the north poles facing out and I have a big sphere with lots magnets embeded in it with all the south poles facing out. I set the ...
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0answers
37 views

Find magnetic field in a solenoid for different regions?

A steady current I flows along an infinitely long hollow cylindrical conductor of radius R. This cylinder is placed coaxially inside an infinite solenoid of radius 2R. The solenoid has n turns per ...
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2answers
41 views

Magnetic field at infinity

Does a magnetic field, generated by permanent magnets (for instance), vanishes "theoretically" (according to Maxwell's equations) at a very long (infinite) distance from the magnetizing devise? What ...
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1answer
34 views

Can two transformers used to make tesla coils?

Tesla coils seem to perform the same as a transformers: they use two coils and use magnetic field to transfer the energy. Doesn't using two transformers produce the same result? It doesn't seem to be ...
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0answers
34 views

What happens to a superconductor when a magnetic fields strength increases?

I'm curious about what happens when a HTS is locked in place above a magnet via the Meissner Effect and say another magnet is added. Would the superconductors height fluctuate? Or would the extra ...
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2answers
37 views

Magnetic Hysteresis

I'm a bit confused about when magnetic hysteresis occurs in ferromagnetic materials. Does it only occur with a rapidly changing external magnetic field or with a slowly changing field? Does the speed ...
6
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1answer
68 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 ...
0
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1answer
25 views

energy in a current induced magnetic field

a mass of metal is near a current carrying wire, say a DC current. the metal feels a magnetic force of attraction and moves toward the wire overcoming some kinetic friction. the work done by the field ...
0
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1answer
67 views

Did the derivation of self inductance equation overcalculate winding number? [duplicate]

Let $L , I , \phi$ are self inductance , current and magnetic flux (created by each loop) of a solenoid with $n$ turns . $r$ is the radius of those loops . We have , $LI=n \phi = nAB $ [$A=\pi r^2$] ...
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0answers
53 views

Induced current created by a magnet falling in a copper tube?

One of the educational demos often shown in schools is to drop a high strength neodymium magnet down a length of copper tube. It takes a considerable time to exit the tube because as it falls it ...
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0answers
28 views

How can you relate magnetic dipole moment using bound current density?

This was on my midterm last week, the question ask us to use bound current density to compute magnetic dipole moment
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1answer
53 views

Closed and Open Electromagnetic Cores

I think I may understand this concept, but I haven't been able to verify with anyone that I'm going about this the right way. So when a wire is wrapped around a core that is a closed loop, like a ...
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0answers
29 views

Force and Torque being applied off-center due to magnetic forces [duplicate]

Say that I have two magnetic dipoles, one of which is rigidly attached to a freely movable inflexible body at some point that is not at the body's center of mass, while the other is fixed in space. ...
2
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1answer
46 views

About Right-Hand-Rule and Cross Projuct

In "Physics for Scientists and Engineers with Modern Physics - 8th Edition", p. 842, it gives the total magnetic force on the segment of current-carrying wire of length $L$ in a uniform magnetic ...
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0answers
30 views

How to find force acting on ferromagnetic material when it is placed in external magnetic field?

When we bring magnet towards ferromagnetic material ( like iron nails), then material gets attracted towards magnet. Since there is motion of material, there must be force acting on it. How to find ...
0
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1answer
31 views

Does zero free current entail zero $\vec H$?

There are two kinds of magnetic fields (different authors give them different names), $\vec B $ and $\vec H$ which are related by the equation $$ \vec B = \mu_o (\vec H + \vec M)$$ where $\vec M$ is ...
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3answers
181 views

Do mobile phones produce radiation harmful to humans? [closed]

What are the health effects of mobile phone radiation (if any)? Does using a mobile phone without an SIM card change the answer?
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1answer
39 views

Can I tear apart a pipe with magnetostriction? And how big field should I use?

As I know, with magnetostriction we can "stretch" its unit cell. The stronger is the field, the more it expands the cell. Using alternating current in coils that induce magnetic field we can stretch ...
2
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4answers
245 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 ...
2
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2answers
58 views

Divergence of Magnetic Field in an Electromagnetic Wave

In many text books of physics (especially those coping with Electromagnetic Theory), we see that an electromagnetic wave (EMW) is drawn as an electric field varying with a sinusoidal form and exactly ...
0
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1answer
164 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)?
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0answers
50 views

Magnetic field derived from a scalar function

Question: Show that $\mathbf B = \hat r \times \nabla g(\mathbf r)$, where $g$ is an arbitrary scalar function, is a plausible magnetic field. What current density $\mathbf J $ can produce ...
2
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0answers
121 views

Field at the tip of a rotating cone. Is (THIS STEP) in my solution right? [closed]

** Edited: I'm going to CLARIFY where and what my question is. Problem: A hollow cone(like a party hat) has vertex angle $2\theta$, slant height $L$, and surface charge density $\sigma$. It spins ...
2
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1answer
89 views

How does the electric field pulse propagate during a change in the magnetic vector potential?

The electric field in terms of the electric scalar potential, and the magnetic vector potential is: $E = -\nabla\phi - \frac{\partial A}{\partial t}$, where $A$ is such that $B = \nabla \times A$. ...
3
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1answer
37 views

Why are the poles of a magnet reversed when a magnet is split into two?

This question may be odd, but today i noticed something when my little magnet split into two pieces. The poles reversed, so they could not get into "one piece" again (because the poles was ...
0
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1answer
45 views

Mimic Magnetic Repulsive Resistance through a spring

I have two identical magnets and I push them towards each other so that they are repelling. Is it possible to accurately mimic this repulsion effect (magnetic energy) just using a metal spring ...
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2answers
162 views

Magnetic force as a relativistic effect?

There is something I am confused about when it comes to the force between two parallel wires carrying current, specifically why when they carry current in the same direction the wires are always ...
0
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1answer
33 views

Magnetic interaction of wire and rectangular loop

In this video, Prof. Lewin shows an infinitely long wire and a rectangular loop at a distance $r_1$ from each other, each carrying a current. He then calculates the magnetic field resulting from the ...
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0answers
17 views

Strongest Magnet Material - Theoretical Limits?

In terms of field strength the current best (AFAIK) is NdFeB with small magnets capable of producing strengths on the order of one Tesla. Is there a theoretical upper limit on the field strength of ...
1
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1answer
109 views

Magnetic levitation frog example

I'm trying to figure out the strength of the magnetic field needed to levitate the frog, assuming it's spherical, has mass $5$kg and diameter $20$cm. I also assume $\vec{B}$ is uniform. Since it's ...
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1answer
47 views

What is the magnetic field on surface of a current carrying conductor?

Biot Savart's law says there should be none as the current element is along the displacement vector, hence as $\sin \theta = 0$, so, the magnetic field must be zero. But, as per Ampere's loop rule ...
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3answers
624 views

Why in a solenoid, do the magnetic field lines resemble that of a bar magnet?

Each loop in the solenoid will have its own magnetic field wrapped around it. In that case it won't resemble the magnetic lines formed by a bar magnet...; but we see that it is the same. Why is that?
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0answers
74 views

Electrolysis of Paramagnetic Ferric Chloride in Water

I'm trying to settle a bit of a debate between a friend and myself over the cause of an effect observed when dissolving Ferric Chloride, Iron(III) Chloride (FeCl3), in water and supplying an ...
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0answers
21 views

Calculate rotational duration of magnetic levitation inside a vacuum chamber?

Background Numerous examples show rotating pyrolytic graphite (or similar diamagnetic material) that can be moved using a laser. Problem The problem has the following objects: An N52 grade ...
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0answers
61 views

How to prove that the net magnetic force in an arbitrary current loop is zero [closed]

I believe that using Stokes' theorem makes this a laughing matter, because $$\mathbf{F}=\oint_C i d\mathbf{r} \times \mathbf{B}$$ Since the magnetic field is constant the $\nabla$ operator would ...
9
votes
2answers
15k 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. ...
0
votes
1answer
36 views

How is anti-hydrogen captured?

Knowing that the overall charge is zero, what mechanisms/technologies are used to capture anti-hydrogen? Where is it stored until annihilation? I am aware of magnetic traps being used to edge the ...
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2answers
45 views

How does the Earth's magnetic field interact with objects?

I'm not a physicist so I was wondering how objects and the Earth's magnetic field interact with each other. For instance: does any of them modify the other in any way? can an object be damaged by the ...
0
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2answers
88 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
65 views

AC wire radiation

I'm trying to test my recently installed MEEP program for a very simple AC current. I know that for DC current, Ampere's law dictates that the magnetic fields must drop off as 1/r. How does this ...
1
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1answer
72 views

Magnetic field of a static disk magnet

I have a magnetic disk (Radius R, height h) that creates magnetic field lines (axisymmetrical). I simulated the field lines, exported the data and am now trying to fit a function into the data to have ...
0
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0answers
21 views

Near field and Nuclear magnetic resonance (NMR)

Why does Nuclear Magnetic Resonance (NMR) physics not concern itself with near field physics? All resonance wavelengths in NMR are much larger than bough sample, pick-up coil and excitation coil. ...
0
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1answer
78 views

Magnetic dipole and magnetic moment

I don't quite understand the meaning of these terms. My physics book just gives the mathematical definition of magnetic moment as µ=IA, which means nothing to me. I know it has to do with torque. ...
0
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2answers
47 views

Do transmitters create magnetic fields and radiation?

In the company I work for (I am a software engineer) we develop a system which uses a transmitter (antenna) that creates a magnetic field. I also know that radio station transmitters create radio ...
5
votes
1answer
206 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 ...
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0answers
47 views

Calculation of Magnetic Field Lines

I am doing some research on how to calculate magnetic field lines for a bar magnet. So far I have found the following equations: \begin{align} \frac{B_r}{B_\theta} &= \frac{d_r}{rd_\theta}\\ ...
0
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1answer
44 views

Foucault currents with a simple pendulum

I have this diagram : It's a kind of pendulum; when it swings, it passes through a small aera where there is a magnetic field. Therefore, the electrons moves towards the bottom because of a Lorentz ...
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1answer
159 views

Why can we detect a magnetic field, but not an electric field around an AC current?

Consider a wire through which an AC current is passing. Because of the AC current there is an alternating magnetic field present around the wire and because of the alternating magnetic field there ...
1
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1answer
92 views

Numerical error with simulation of electric charge in homogeneous magnetic field [closed]

So, I am trying to make an 2D animation of electric charge in homogeneous magnetic field which is perpendicular to charge's velocity. I've got the "circular" motion but the problem is that the speed ...