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.
4,795
questions
3
votes
1
answer
1k
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 no ...
CommunityBot
- 1
0
votes
2
answers
24
views
Energy density due to magnetization and magnetic field
Equation (20) (see page 3) of "Interactions between uniformly magnetized spheres" by Edwards et al. states that the energy density associated with sphere $j$ due to the magnetic field $\...
- 822
3
votes
2
answers
102
views
What are the main sources of magnetic fields?
Is the generation of magnetic fields mainly due to certain spins of particles and the movement of electric charges?
I mean fundamentally what are the sources. I recognize in aggregate, whatever ...
- 14.9k
0
votes
1
answer
186
views
How can flux linkage (a 3D concept) be defined for a cross section?
The authors of Power Systems Analysis calculate the inductance per unit length (henrys/meter) of a transmission line attributed only to the flux inside the conductor as "flux linkages per ampere.&...
CommunityBot
- 1
1
vote
0
answers
30
views
Schwinger approach using the heat kernel [closed]
I am having trouble calculating the effective action for a constant magnetic background. The calculations I am trying to replicate are from this paper: https://arxiv.org/abs/hep-th/9807031 . The ...
- 209k
0
votes
1
answer
200
views
Finding Magnetic Field of Coil (Wound around a core)
I have seen in the book that the answer would be same as that of an infinitely long wire $\frac{\mu_0 I}{2\pi a }$ how can we prove that though? I'm really not convinced and have tried to prove it ...
CommunityBot
- 1
0
votes
1
answer
394
views
Expression for external magnetic field of a cylindrical bar magnet?
I would like to calculate the magnetic force of a cylindrical bar magnet on a steel ball bearing, which is a distance away in a straight line from one of its poles. What is the expression for this?
...
CommunityBot
- 1
0
votes
1
answer
448
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, Ampère's law dictates that the magnetic fields must drop off as $1/r$. How does this ...
CommunityBot
- 1
0
votes
1
answer
79
views
Are the accelerated charges the real reason for the magnetic induction? [closed]
I have watched an explanatory video from YouTube that stated that the real reason for the "magnetic induction" are electric field lines of an accelerated charge, that have a component in the ...
- 39.7k
1
vote
1
answer
547
views
What is the Torque experienced by a Circular current carrying loop placed parallel to a uniform Magnetic field by Calculus method?
IF we take small element in the circular loop then it must experience a magnetic force in a direction coming out or going into the plane of coil(depends on both the direction of magnetic field and the ...
CommunityBot
- 1
8
votes
4
answers
28k
views
1 Tesla electromagnet?
Is it possible to create a powerful electromagnet at home?
With use of a ferromagnet it seems so...
Using the following formula: $B(Tesla)= k\mu_0nI$. I understand some ferromagnet's like iron could ...
2
votes
4
answers
844
views
What happens if I have a square conducting wire being permeated by a magnetic field and the field suddenly disappears?
Suppose there is a square conducting wire in a magnetic field. The two vertical branches will have the same emf, and the two horizontal branches will have 0 emf, resulting in a net emf of zero and ...
CommunityBot
- 1
0
votes
2
answers
629
views
Is the induced electric field generated due to the separation of charges in a moving wire in a magnetic field non-conservative?
As the title suggests, whenever there is a moving wire in a magnetic field of constant magnitude, an induced voltage is produced. Now, due to the separation of charges, which is a result of the ...
CommunityBot
- 1
9
votes
1
answer
103
views
Should electrons as tiny magnets, stick to a permanent magnet if in appropriate conditions?
Should electrons as tiny magnets, stick to a permanent magnet if in appropriate conditions? Why shouldn't the magnet collect them like tiny iron dust?I know they repeal each other but should a certain ...
- 51
3
votes
2
answers
321
views
How does a magnetic field do work on rotating a current loop?
Lorentz force tells us that the force on a charged particle by a magnetic field is always perpendicular to its velocity. So its a pretty well known fact that a magnetic field doesn't do work.
But we ...
CommunityBot
- 1
1
vote
2
answers
74
views
Why does the tension change instead of the speed of this object undergoing circular motion?
I recently came across the following problem:
A charged particle is whirled in a horizontal circle on a frictionless table, by attaching it to a string fixed at one end. If a magnetic field is ...
- 628
0
votes
1
answer
54
views
What is the electric field inside an inductor?
In a simple LC oscillation a charged particle was kept in the centre of solenoid ie inductor. At t = 0 will it experience any force? According to me since the particle is in center it won't ...
- 38
2
votes
2
answers
276
views
How is the magnetic flux density inside a current tube affected by an inner wire?
Background to problem
Conventional wisdom informs that the magnetic flux density inside a tube carrying current is zero everywhere. Pictorially this is represented by this finite element analysis (...
CommunityBot
- 1
2
votes
2
answers
498
views
Magnetic Field Lines Vs Magnetic Vector field
I am studying electromagnetic theory and when I started researching the history of conventions used in magnetic interactions I could not get them. The basics of how they modelled the magnetic ...
CommunityBot
- 1
2
votes
1
answer
238
views
Amperian loop and magnetic field
Suppose I have a long solenoid with $n$ turns per unit length. The electric current through the solenoid is changing and I am interested in finding the magnetic field $(B)$ inside. So, we choose an ...
CommunityBot
- 1
0
votes
2
answers
1k
views
Why is the magnetic field in the center of a coil the strongest
In my current lab we were told that we should expect the magnetic field of a coil to be strongest in the center of the coil.
I was wondering why this is the case. Shouldn't the magnetic field just be ...
- 3,112
0
votes
1
answer
29
views
Induced emf and coil winding direction
Recently, I've learned that induced emf is there to oppose the change in magnetic flux.
consider a current increasing over time ($\frac{di}{dt}>0)$, moving left to right as it passes through the ...
- 16.9k
1
vote
1
answer
463
views
Potential Drop across Inductor VS Potential drop across Rotating coils in $B$-Field
I was trying to understand the difference between the Back emf generated across Inductor due to change in current and Back Emf Generated across a coil that is rotating in presence of B Field.
...
CommunityBot
- 1
0
votes
0
answers
19
views
Voltage and current excitation in diffusion equation
Dear Physics community,
i am having trouble with the diffusion equation and the Maxwell equations. I am investigating a system where a voltage is the source of eddy currents. However, most established ...
- 23
0
votes
1
answer
226
views
How would the field in between two semi-infinite solenoids placed next to each other look like?
Suppose two semi-infinite solenoids placed next to each other are separated by a small gap as shown below
If the solenoids are identical to each other, What would you expect the field in between the ...
- 3,112
0
votes
2
answers
59
views
How many times do you need to drop a magnet for it to lose it's power? [closed]
How many times do you need to drop a magnet to the ground for it to lose it's power ?
Is there a way this is measured ?
Thanks!
- 96.7k
-1
votes
0
answers
48
views
Direct derivation of retarded fields in electrodynamics
Rather than first selecting a specific gauge, writing a guessed solution for the potentials within that gauge, and then differentiating them to obtain the fields, can we instead directly derive the ...
1
vote
1
answer
297
views
Magnetism and reactionless drives
I have a question regarding the interactions of electromagnetic fields.
Say you have two superconducting electromagnets A and B. The properties of the magnets are known such that you can tell ...
CommunityBot
- 1
1
vote
1
answer
243
views
Is this a correct way of finding magnetic field of a magnet created with Wasilewski's method?
$\quad$ Wasilewski's method (Or the method that could be seen in Dr Stone episode 9) consists of piece of iron being struck by a lightning, which then magnetises it. Let's say, we have a cylindrical ...
CommunityBot
- 1
-2
votes
1
answer
55
views
Changing the magnetic field of earth
I am familiar with the concept of toroid which causes an electromagnetic field.
Is it possible, if we make a large enough toroid, to change the magnetic field of earth.
If yes, then how will it affect ...
- 1,784
0
votes
1
answer
42
views
Find the leading $1/L$ corrections to the magnetic field for a finite solenoid of length $L$
I found this exercise in the book Classical Electromagnetism in a Nutshell by Anupam Garg, on page 103 and chapter 24 about vector potential
I can find the magnetic field of the solenoid with length $...
- 6,699
2
votes
3
answers
2k
views
How does a magnet cause magnetic force and its magnitude/direction?
Magnetic fields are created due to electron spin in the magnet. But how exactly does an electron "spinning" create forces around the magnet? Also, the magnetic force on a charge moving in the magnetic ...
CommunityBot
- 1
0
votes
1
answer
225
views
Why is there no deflecting force between two bar magnets?
If we were to hypothetically place a magnet to the right of the magnet above with the North pole of the right magnet next to the South pole of the left magnet, from real-life experience, I know that ...
CommunityBot
- 1
0
votes
1
answer
1k
views
Force on a current carrying loop in a non-uniform magnetic field
I was taught that a current carrying loop in a non-uniform magnetic field will always experience both a torque and a net force.
Is this always true? I can't think of any examples where the force would ...
CommunityBot
- 1
0
votes
1
answer
39
views
Why do passive materials impact magnetic field? [duplicate]
When calibrating magnetometers you need to consider the soft-iron distortions, from my understanding they are basically passive materials that deform the magnetic field.
I'm curious why these passive ...
- 57.6k
0
votes
1
answer
249
views
Knowing the force of attraction of two bar magnets what is the force between two surfaces made of the same material?
Two bar magnets with area $a$, in axis, at a distance of $d$ ($d$ is much biffer than $a$) attract each other with a force of $F$.
What is the force between two infinite surfaces made of the same ...
CommunityBot
- 1
2
votes
2
answers
1k
views
Trying to visually understand Ampere's Law
When deriving the magnetic field due to a current carrying wire, if we choose a circular Amperian loop, we can state:
$$\oint \vec B \ \cdot d\vec s = \mu_0 \ I$$
But due to the symmetry of the ...
CommunityBot
- 1
1
vote
1
answer
33
views
Solve for the shape and curvature of Earth's magnetic field
How can I solve for the shape of Earth's magnetic field (neglecting the effects of the solar wind which distort it). It looks very similar to the field due to a solenoid, but I can only find solutions ...
- 36.7k
4
votes
2
answers
255
views
Edge states at high magnetic field (Quantum ballistic transport)
I am learning about edge states at high magnetic field (Quantum ballistic sample). What I understand so far from it is that at high magnetic field, Landau states arise.
Then (I don't know exactly ...
- 209k
0
votes
2
answers
81
views
Violation of work-energy theorem (WET) in deriving potential energy (PE) of current-carrying ring in a uniform magnetic field
In deriving the potential energy (PE) of a current carrying ring placed in a uniform magnetic field rotated from $ \theta_1 \to \theta_2$, we write:
$$ \int dW = \int \tau(\theta)d\theta$$
under the ...
- 39.7k
4
votes
2
answers
5k
views
How can magnetic flux be a scalar but magnetic flux density is a vector?
I know flux is a scalar (slightly confused how this can be negative, as scalars don't take direction into account) but if flux density is flux*Area, how can multiplying be another scaler yield a ...
1
vote
0
answers
26
views
Magnetic shielding, Superposition and "Guiding Field Lines"
Suppose a permanent magnet and an iron plate.
The iron plate is put into the vicinity of the permanent magnet. Hence the iron plate takes up some specific magnetization state. Behind the iron plate, ...
- 111
2
votes
2
answers
11k
views
Calculating magnetic field strength for a very small electromagnet
I am trying to calculate the magnetic field (in tesla/gauss) of an electromagnet that is very small and has very few windings. For example 12 windings over 0.003 meters. I know this is not going to ...
CommunityBot
- 1
1
vote
2
answers
254
views
How to find the magnetization of a neodymium magnet?
I am interested in knowing how to find the value for Magnetisation of cylindrical N35 neodymium magnets based on the information sheet, or through the means of an experiment. This is to calculate its ...
- 822
0
votes
1
answer
252
views
Can you increase the magnetism of a material by increasing the heat?
EPFL scientists have provided the first evidence ever that it is
possible to generate a magnetic field by using heat instead of
electricity.
https://actu.epfl.ch/news/using-heat-to-make-magnets/
Can ...
CommunityBot
- 1
3
votes
4
answers
2k
views
Why does the electric field and not the magnetic field remains in the same direction after reflection from a medium?
I was reading up about reflection and transmission when an electromagnetic wave is normally incident on a surface.
I came across this figure :
My question is why is the direction of electric field ...
CommunityBot
- 1
1
vote
1
answer
323
views
How to calculate retarded potential (for magnetic field calculation) for a group of current carrying loops where the magnitude of current is changing?
For constant current, the magnetic field seems to be easy to calculate because of Biot-Savart Law. For a loop having varying magnitude of current (simplifying an electromagnet), however, it seems that ...
CommunityBot
- 1
0
votes
2
answers
1k
views
Ferromagnetism and induced magnetism
According to Wikipedia:
A magnetic domain is a region within a magnetic material where individual magnetic moments of the atoms are aligned with one another and point in the same direction thus ...
CommunityBot
- 1
2
votes
2
answers
407
views
Would mechanically moving electrons create a super-strong magnetic field?
According to this Veritasium video, the magnetic field in a wire with a non-zero current is an artifact of special relativity. A moving charge sees a speed difference between the wire and the ...
CommunityBot
- 1
2
votes
2
answers
1k
views
Off-axis magnetic field strength for permanent magnet calculation/equation
I'm working on a project which uses cylindrical permanent magnets, and I'm trying to determine the expected magnetic field due to these magnets. One problem I run into is that these magnets are ...
CommunityBot
- 1