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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2answers
84 views

Do transformers lose energy?

EDIT: The title should rather be how/why transformers lose energy My idea of a transformer is that it is composed of two separate wire windings around some metal core. The purpose is to ...
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5answers
116 views

How do magnetic field lines cancel outside of a solenoid?

Please explain me briefly, how magnetic field lines cancel outside solenoid? There is only one wire wrapping it and therefore only one direction of current so how can magnetic field cancel out? How ...
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0answers
23 views

What cause the variation of inductance in inductor having ferromagnetic core?

If the core is ferromagnetic then the permeability vary as the increase of flux density or magnetic field strength cause by the increase of current and so the inductance can vary as $$L=\mu_0\mu_r ...
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0answers
29 views

Conductors - force needed to maintain a constant velocity

There runs a current $I_0$ through a straight and long conductor. Two more conductors are placed parallel to it in a plane with distances a and b respectively. The resistance of the connection is ...
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1answer
116 views

NOT Perpetual Motion; Could It Work?

TL;DR The energy is not being created freely, so why shouldn't it work? We have all seen the YouTube "perpetual motion" machines. You know, the computer fans with magnets taped on them and hidden 9 ...
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0answers
31 views

Flux cutting in a uniform magnetic field

Say we have a uniform magnetic field acting into the page, and we have a bicycle wheel which is spinning at a constant tangential velocity $v$. Each spoke has a equal length, $l$. Reading has told me ...
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0answers
31 views

Magnetic forces [closed]

Can we generate magnetic field forces for pushing or pulling devices? How much weight can be pulled by electromagnetic field?
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2answers
36 views

Change of magnetic flux on size of magnetic field and area

Consider a solenoid with 50 turns. Each turn gives has an area $A$. When the power is switched on, each turn produces a magnetic field of 1 Tesla. What is the total change in magnetic flux when the ...
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2answers
48 views

If I double the amount of oxygen molecules, do I double the paramagnetic force?

Oxygen is well known to be paramagnetic. If I take one molecule, $O_2$, and measure its paramagnetic force due to externally applied magnetic field, and then add another molecule near the first ...
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0answers
26 views

The magnetic field strength/intensity produced by the coil is always $\frac{NI}{l}$?

By comparison between electric field and magnetic field. The relationship between H and B is analogous to E-D relationship that $$B=\frac{H}{\mu_0}$$ as same as $$D=\frac{E}{\epsilon_0}$$ However ...
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0answers
27 views

Does a magnet floating over a superconductor slowly fall and take infinite time to stabilize?

The reasoning being that as the magnet moves towards the superconductor it induces an opposite magnetic field, until the latter rises sufficiently to equal the weight of the magnet. Except that looks ...
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0answers
117 views

Confused on how to apply the volume integral form of the Biot-Savart law

In Viscous evolution of point vortex equilibria (Jing, 2011) the author explains that the velocity equation for the Lamb-Oseen vortex is found by applying the 2D Biot-Savart law to the vorticity ...
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1answer
30 views

Does the wireless energy tranmission affect compass

Wireless energy using magnetic inductive coupling. So magnetic field will be affect around device. We use it to charge mobile device so I wonder if it will affect compass in our device
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2answers
36 views

Equation of a Magnetic Flux Line

I have a simple problem that I am not quite sure how approach: Consider a spatially nonuniform magnetostatic field expressed in terms of a Cartesian coordinate system by $\textbf{B}(x,z) = ...
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0answers
37 views

Longitudinal Adiabatic Invariant in Magnetic Mirror

I am trying to solve the following problem from Bittencourt's Fundamentals of Plasma Physics (Problem 3.4). I have posted an attempted solution below the problem statement: Consider a system of ...
3
votes
2answers
87 views

What are diamagnets and paramagnets?

A paragraph in my text reads: An atom or ion with all electrons paired is not attracted by strong magnets and is termed 'diamagnetic'. In contrast, spins do not cancel when unpaired electrons are ...
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0answers
25 views

Wire loop in the magnetic field

I have strange problem, and no idea how to solve it. The wire loop $ ABCD $ is in a magnetic field of the long thin rod magnet with a magnetic moment per unit volume of $\mathfrak{M} _0 $ and a ...
1
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1answer
20 views

understanding shceme field lines - magnetic field

I would like to know if the magnetic field is in "the x-y plane". Does this mean the field lines are actually parallel to the visible line x or y? Or does it mean the field lines are parallel to the ...
3
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0answers
36 views

Lifting capacity of superconductors

How does the strength of the magnetic field the superconductor is exposed to affect its ability to levitate/lock heavier objects? Or is there no relationship (for superconductors) between magnetic ...
1
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0answers
22 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
19 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
48 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
26 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 ...
1
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0answers
41 views

understanding magnetic dipole moment and torque [closed]

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
27 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
12 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
56 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
211 views
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0answers
40 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
104 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
65 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 ...
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0answers
48 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
votes
2answers
88 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 ...
0
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2answers
62 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
28 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 ...
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1answer
32 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
548 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
44 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 ...
0
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0answers
51 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.
2
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1answer
108 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
votes
1answer
100 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
votes
1answer
38 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
15 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
101 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
58 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
296 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.
1
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1answer
18 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 ...
1
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1answer
49 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
votes
0answers
68 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 ...