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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With what frequency triangle swings if it shuns from equilibrium?

Guide V-shaped is with no friction in the swivel bearings A and B (see Fig.) Of the magnet with a vertical magnetic field of 0.8 T. The weight of the guide is 50 g, the length AB 4 cm, and the length ...
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0answers
11 views

Nuclear powered flux compression generator?

A flux compression generator is a device for converting the chemical energy of explosives into magnetic field energy, with reported efficiencies of up to 20%. Is there a limit on the conversion ...
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0answers
9 views

Electric potential at the wings of a plane

PROBLEM: A plane with wing span 70 meters is flying with a speed of 100 m/s in a uniform magnetic field B = 5 T that is directed vertically with respect to the wingspan. What is the emf produced ...
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0answers
17 views

What is strength of an electromagnet at a distance?

I want to levitate a permanent magnet between two electromagnets. My two governing equations are: $$F = \frac{B^{2}A}{{2\mu_{0}}}\tag{1}$$ $$B = \frac{NI\mu}{L}\tag{2}$$ Where $x$ is the distance ...
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0answers
16 views

Magnetic field along the line which is perpendicular to the wires

Suppose we have 3 wires which cross at some point $A$. After the branching point, the electric currents in two arms are $I$. And we have the line passing through the point $A$ and perpendicular to the ...
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0answers
49 views

Which is the true magnetic field?

In electromagnetism we have the $\mathbf{B}$ field which is the field appearing in the Lorentz force law: $$\mathbf{F} = q(\mathbf{E} + \mathbf{v}\times \mathbf{B})$$ and we have the $\mathbf{H}$ ...
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0answers
20 views

understanding magnetic dipole moment and torque [on hold]

I would like yo know if I understand things correctly: Magnetic moment, which is a constant value for a solenoid or magnetic dipole, determines the torque it will experience in a magnetic field. (I ...
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1answer
16 views

Magnetic field between two rings

Two rings are placed parallel atop each other along an axis with a distance $\epsilon$ which is much smaller than the radius of both rings a. Through one of the rings there is a current I and through ...
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0answers
30 views

Can a magnetic field be expelled over long arbitrary distances through a super conductor? [on hold]

I'm not a physiscist but i have a creative concept I wish to make into a environmental commercial before my Interactive Feature Film. Apologies, if it sounds like I have no idea what I'm talking ...
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0answers
35 views

Finding the magnetic field [on hold]

A mechanical pendulum is made of a metal rod, one end of which is attached to a string. The mass of the rod is $m$ and the string length is $l$. The oscillation period of the thus obtained pendulum ...
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0answers
10 views

from control torque to magnetic moment

I am designing a system which generates a magnetic field to make itself move in space (a cubesat with magnetorquers). This magnetic field is known as the magnetic control torque, i.e. it will torque ...
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1answer
52 views

Has the effect of magnetic fields on time ever been examined experimentally?

Relativity of time can be examined with satellites as gravitational or acceleration. Is there any similar experiment with intense magnetic fields?
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4answers
131 views
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0answers
21 views

Why is emf 0 for coil rotating in field?

Say you have a coil (that can carry a current) rotating in the field between two magnets. When the area of the coil is perpendicular to the field lines the emf induced in the coil is 0, why is this?
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2answers
53 views

Magnetic field outside an infinite solenoid

Can someone explain to me how the magnetic field cancels outside a solenoid of infinite length mathematically (using an integration or something)?
4
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1answer
52 views

How long does it take a magnet to lose its magnetization? [duplicate]

As we all know, a magnet has some magnetization that lets it attract other ferromagnetic materials but I was wondering how long it takes to lose this magnetization? Is it even possible or not?
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0answers
15 views

Can a magnet lose its strength over time? Especially when repulsive magnets are around? [duplicate]

I was thinking of hanging delicate art glass pieces separated by opposing magnets on walls simply using the power of magnets. I was wondering will the opposite poles have any effect on the strength of ...
0
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0answers
38 views

What happens to the magnetic field when the source is turned off?

Suppose you had a magnetic field source in space and a piece of iron a light minute away. Assuming magnetic fields propagate at the speed of light since they are massless, if you turn on the magnetic ...
3
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2answers
59 views

Does a moving charge have additional (magnetic) energy

My understanding so far: A moving charge produces a magnetic field, B, in an analogous way to a current produces one. A magnetic field has an energy density which is proportional to B squared. My ...
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2answers
55 views

Why can a magnet setup not fly?

I know that the following setup won't work to lift it up forever: But I'm struggling to convince myself why. If the top magnet is strong enough to lift the weight, why is the bottom magnet not ...
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1answer
19 views

To describe crystallity structures of this ferromagnetic material

MOKE microscope picture of the ferromagnetic Material $Co_{40} Fe_{40} B_{20}$ of 20 nm thin film All other pictures look the same, also from different angles: [0,360] by 15 degree separation. I ...
0
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1answer
24 views

Definition of magnetic field $H$ in ferromagnetism

I am thinking how you can define explicitly the magnetic field $H$ in a ferromagnetic material. I think the Maxwell's equation should apply. However, I am not completely sure which form. Here are ...
1
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2answers
79 views

Why opposite poles of magnet attract each other, why don't they repel?

We know that different poles of magnet attract each other, but I don't know why this happens why similar poles doesn't attract. what is difference between similar poles and different poles?
1
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1answer
28 views

Is the magnetic field calculated by Ampere's Law only because of the currents crossing the loop? [duplicate]

In Ampere's Law, $$\oint \vec B \cdot \mathrm d \vec l = \mu I$$ the current outside the curve is not included on the right hand side of the equation.* Does it mean that the magnetic ...
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0answers
47 views

What will be the motion of an electron kept at rest in the vicinity of a magnetic monopole?

Consider that both an electron and a magnetic monopole are kept at rest close to each other. Will this result any motion of the electron? If yes, please give a derivation of the equation of motion.
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1answer
29 views

Force on permanent magnet solenoid core

I was wondering, since a coil/solenoid will pull any ferromagnetic material inside it, does the initial magnetization of the object in question affect the magnitude or direction of the force? I know ...
0
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1answer
52 views

What is the magnetic flux density “outside” the solenoid when AC current is passing through it?

I know that there are well defined equations explaining the magnetic flux density in the solenoid. However what about magnetic field outside the solenoid? How is the magnetic flux density related ...
0
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1answer
24 views

Magnetic flux from an infinit wire through a Square loop [closed]

Okay so I need to solve this exercise. I know that the magnitic field from an infinit wire is given by: $ \vec{B} = \frac{\mu_0I}{2\pi r} \hat{\phi}$, And that I must do an intergral looking ...
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0answers
10 views

What is the effect of a magnetic field on a plasma speaker?

I have been doing some research for the past couple years investigating the effect of a magnetic field on a plasma speaker. More specifically, if you apply a relatively uniform magnetic field in no ...
0
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3answers
67 views

In the electric field we have dielectrics.What about the magnetic field?

Do we have insulators in the magnetic field just like we have dielectrics in the electric field? How are they called and how do they work?
1
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1answer
45 views

How does one calculate or even approximate the force observed by a magnet as its dropped inside of a diamagnetic cylinder?

How does one calculate or even approximate the force observed by a magnet as its dropped inside of a diamagnetic cylinder? Wikipedia and Google does not provide much information on this topic. ...
3
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1answer
185 views

Took a picture of my laptop screen with my iPhone. The blue pattern in the image seems to magnetic lines. How is this possible?

The pattern seems consistent with the magnetic force lines of a bar magnet.
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1answer
12 views

Magnetic field path on a surface with axial symmetry

$\newcommand{\dv}[2]{\frac{\mathrm{d} #1}{\mathrm{d}#2}}$ I'm trying to find the path a magnetic field line takes along an axially symmetric magnetic surface. I'm given: - $r,z$ points along a ...
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1answer
40 views

Can Ampere's Circuital law be used on an infinite number of alternating Helmholtz coils?

I have the following surface current density $$ \bar{\sigma}_s = \hat{\phi} \sin(kz) |\bar{\sigma}_s| $$ to approximate an infinite number of alternating Helmholtz coils stacked along the z-axis with ...
2
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0answers
36 views

Graphene - Can it produce a magnetic field?

So it's probably a quick no on this one, but since I haven't majored in physics or chemistry I have no idea if it's possible to make Graphene generate a magnetic field. Assuming power or current is ...
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1answer
38 views

$B$ field around an infinite wire symmetry argument

Consider the infinity current carrying wire wire drawn below along with the three possible components of the magnetic field at a point a distance $r$ from the centre. I know how to use symmetry to ...
3
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0answers
46 views

Why does “liquid metal” do this?

I just watched this video where a guy uses magnetic "liquid metal" along with a standard magnet to create some pretty cool spiky shapes. The magnetized liquid, when brought near the standard magnet, ...
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0answers
25 views

Magneto Optical Kerr Effects

I have a few questions on MOKE setup. Firstly, why is calibration of the coils necessary? Is it to get a relationship between the voltage and the Magnetic field? Secondly, why do we have to normalise ...
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1answer
27 views

How to tell apart a permanent and induced magnet which are otherwise identical?

In his educational series "Demonstrations in Physics" the late Prof. Julius Sumner Miller posed the following riddle: Given two identical bars of iron, one magnetized and one not, how can you ...
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0answers
14 views

Halbach array possible shapes?

Looking at images on the web most hallbachs are either rings or blocks but I have seen a couple pictures of what look to be rectangles or pyramids. They are just illustrations though and maybe ...
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0answers
10 views

Looking for name of mapping procedure [migrated]

I have been searching for a technique that I used 20 years ago, but for the life of me, I cannot remember the name. It is used in visualizations of pressure, temperature, electromagnetic fields etc. ...
2
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1answer
34 views

Relation between magnetic fields of magnets and magnetic field of currents

When I started to study magnetostatics it was said that magnetic fields are created by charges in motion, that is, they are created by currents. On the other hand, we have magnets and those have ...
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1answer
17 views

Local form of Ampere's law

How can I find the magnetic field created by an infinite straight wire of radius $R$ and current density $\vec{j}$ using only the local form of Ampere's law : $\vec{\nabla}\times \vec{B} = \mu_0 ...
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2answers
37 views

Bar magnets and work - contradiction

Suppose we hold two bar magnets with opposite poles facing each other a certain distance away. We let go and the magnets fly towards each other. We observe that the magnets gain kinetic energy. ...
3
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1answer
113 views

Why is the quench temperature fluctuation not a concern for maglev trains?

I am having trouble discovering why temperature fluctuations and magnetic field fluctuations are not a stability concern for superconducting magnetic levitation trains. I am under the impression that ...
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0answers
115 views

Earth magnetic field [closed]

I gather that, in these days, the most common explanation for the Earth magnetic field existence and strength is the theory of convetive currents of molten iron and nickel atoms in the outer core of ...
0
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2answers
23 views

How does magnetic field affects a charge?

If a electron is placed in a fixed magnetic field, how the electron will get influenced by it? How does magnetic field attacts/repulses the charge?
2
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1answer
62 views

Magnetic monopoles and special relativity

I was thinking about magnetism as a product of special relativity and the result of this approach to the magnetic monopoles. So if magnetism is a product of electricity(like electricity from another ...
5
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7answers
310 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 ...
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0answers
30 views

Do these symmetrical looking B field problems have the obvious answer?

I am struggling with two questions whose answers both appear to be trivially zero by symmetry arguments, when I was expecting more derivation to be required. Problem A), An infinitely long wire ...