# 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 do units work out in a magnet's flux density vector field?

I was reading this question about the vector field around a magnet, because it happened to be my question exactly. Only, I didn't like the answer at all. I want a function that returns a vector of the ...
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### I came across with the following magnet wheel image. As shown the North and South poles belong to two different Parts. How can this be explained?

In the inline image the mentioned magnet is shown As I know if I split a magnet, each one of the two halves of the body will acquire a north and a south pole but this comes in contrast with what's ...
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### What is the proof of Earnshaw's theorem in this context?

I am a mathematician and do not know much physics so I would appreciate your explanations very much. In my understanding, Earnshaw's theorem says that there are two stable stationary configurations, ...
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### Physical interpretation of Inverse Square Model

Attempted to model the extreme work done in 2D by a force acting to obey inverse square law which is so important in physics (Gravitation, electromagnetics, electrostatics, Coulomb's law of forces ...
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### Deeper explanation of why Spin-Echo's 180 degree refocusing pulse recovers static magnetic field inhomogeneities vs Gradien-Echo which does not

I have studied the Spin-Echo pulse sequence for some time now, and read many explanations in different books and courses. I know that the 180 degrees RF pulse (applied half way between the 90 degrees ...
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### Magnetic Field of Solid Circular Current Loop [closed]

I'm looking for an analytical expression for the magnetic field around/within a solid circular current loop carrying static current. An analytical formula for the magnetic field around a circular loop ...
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### Magnetic field generated from constant coplanar concentric circular electric current

Let electric current run in coplanar concentric circles with radii extending from $0$ to infinity. The current all run in the same circular tangential direction. The current line density across the ...
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### Permeability in equation of field due to ideal solenoid

The magnetic field well inside a long solenoid is given by $\mu_0 n i$, where $n$ is the number of turns per unit length and $i$ is current flowing in the tightly wound wire. However, I'm confused ...
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### Why is there an electric field but not magnetic field on the LHS of the integral form of Faraday's Law

Just started to learn Electromagnetism, and didn't quite understand, please help correct my misunderstanding: The lectures said that the electromotive force (e.m.f), was  {\cal E} = \oint \vec{F} \...
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1 vote
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### Magnetic Background Field Correction Methods for ground surveys to detect anomalies

For magnetic ground surveys, I would like to subtract the regional magnetic field, to have an anomaly distribution. What are the most sophisticated ways to do so, except than simply subtracting the ...
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### How are magnets magnetised commercially? [closed]

Basically what the title says I could not find any info on YouTube or safari. The only video I found was the how it’s made video which simply states that an em pulse is used but not the type of em ...
1 vote
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### Is it possible to derive $E$ field and $B$ field of a system that is fairly non-symmetric at every point in space? [closed]

While learning electro and magneto statics for the first time we derived formulae for very specific systems like infinite wire, cylinder, infinite sheet, ring, disc etc. These usually required heavy ...
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### How to find work done by friction in this case? [closed]

The question is this: A circular tube of small thickness having outer radius r = R/2 is fixed in gravity free space. Magnetic field of strength B is present perpendicular to plane of circular tube as ...
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### Curl of current density in a wire with variable cross section

We have a wire with the shape of a cone. The cone is aligned along the z-azis. Major radius $r_M$ and minor radius $r_m$ and length $l$. An electric current $I_0$ is injected at the bottom. We could ...
36 views

### Motion of proton helical forever or not in a region where Magnetic field, Electric field are Parallel to the $x$-Axis? and is the radius increasing? [closed]

suppose there is a proton projected at angle theta to the positive x axis in a region where magnetic field and electric field is parallel to +ve x axis and is pointing towards +ve x axis then in the ...
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### Do flourescent tube lights create magnetic fields like other conductors?

So, does every electron flow also have a corresponding magnetic field to go along with it, or is magnetic fields only a property of solid metal conductors? Also, what about lightning?
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### What is the cause of magnetization?

the relation between magnetic field strength and magnetic influx is: $H=B/\mu-M$. M is called magnetization. In case of magnetic bar, it exists only inside the bar. The relation is shown in this ...
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### Is Lorentz force velocity dependent or length dependent?

I am trying to research Lorentz force for a project I am doing and something that has troubled me is whether or not Lorentz forces depend on the velocity of a charged particle or whether they depend ...
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Sorry if my Q is simple, I'm still in high school. I'm currently arguing with my physics teacher regarding a Q, shown below. The answers state this. However, I am attempting to argue that the ...
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### Why is the angle of declination greater at higher latitudes and lower near equator?

Why is the magnetic angle of declination greater at higher latitudes? If I take a point 'Q' on the Earth's surface as in this figure: (I edited this picture off the internet, so the plane isn't very ...
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### How to calculate magnetic field strength of a solenoid from a certain distance?

Say we have a solenoid meant for creating large electromagnetic fields . If this electromagnet had an amperage of 150 amperes, 1100 turns, a length of 10 centimetres, iron core with a permeability of ...
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### Does the Earth's Magnetic Field Affect Sleeping Position? [closed]

Does the Earth's magnetic field affect the sleeping position of a person? For sleep experience with Nature sounds, check out this video: https://www.youtube.com/watch?v=5FzjrdiUr90
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### How to find permeability of a magnetic material?

I have been working with magnetic materials for quite some time now and never really explored this fundamental parameter. After looking through the literature I realize there and quite few different ...
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### Ampere's law on solenoid, using a circular loop

Suppose we take a long and tightly wound solenoid with current I going in it. We can find the field inside, by ampere's law, taking a rectangular loop and assuming the magnetic field just outside the ...
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1 vote
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### Does electric and magnetic field from electromagnetic radiation are 2D based? [closed]

I'm getting into physics, specially in electromagnetism. When we're talking about electromagnetic radiation. Does it has a 2D shape when it's propagating through space? Does Maxwell's equations ...
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### How can we find the angle between areal vector and magnetic field?

For finding torque we need to find the angle between areal vector and magnetic field. But areal vector makes an angle 37° with the x axis and that means it makes 53° with magnetic field because that's ...
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### What happens when both magnetic field and electric field is applied to a charged particle?

Now what exactly happens when magnetic field and electric field is applied perpendicularly? What happens when they are not perpendicular? In the question, it says that a magnetic field and electric ...
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### In a magnetic field, does the force act on the midpoint of the current carrying wire?

Here, it says that the force acts on the middle points of the wires, but why? What do they mean by when they are saying that the forces 1 and 3 are acting on the same line of action? How does that ...
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### When does magnetic force affect the velocity of a charged particle

So according to this para, I understand that since one component of velocity is perpendicular to magnetic force (and parallel to magnetic field) that component will not change. But other component is ...
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### What is the magnetic field created by a charged square rotating about its center [closed]

In a class on electromagnetism, a question came up where my answer was close to the prescribed answer but not exactly so. I used a different method from the one used in class, and I am not sure if it'...
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