# 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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### Quick question regarding Larmor precession and bar magnets

So I was just reading a bit about magnetic dipole moments, Larmor precession, angular momentum etc., but there was one little thing that was bothering me. As far as I know, any angular momentum will ...
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### Zero work by magnetic field but still motion of particle? [duplicate]

I know from ${\bf F}=q({\bf v}\times {\bf B})$ the force is perpendicular to displacement and so work by magnetic field is always zero. But then how is that a magnet is able to displace any magnetic ...
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### How long does a material's magnetization take to align with an external field?

Take a ferromagnetic material which has been exposed to an external magnetic field $h_0$ for a long time and therefore has and equilibrium magnetization $m_0$. The external magnetic field then flips ...
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### Is there current flowing through a permeant magnet? And could we apply ampere's law for finding field of perm emanant magnet?

https://en.wikipedia.org/wiki/Force_between_magnets In this article, for the ampere model section, wiki talks about how we can think of permeant magnets as having current flowing through them and it ...
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### Magnet tilt - null point relation

Apparently, if a bar magnet held in a horizontal plane on earth is rotated by any angle $\theta$, the null points of the magnetic field rotate by $\frac{\theta}{2}$. My professor just explained this ...
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### Why equal and opposite currents don't cancel while calculating magnetic field on toroid?

Is at point S current entering is not equal to current leaving? I am confused over this concept. Like we have net current zero when we consider a point outside toroid, shown in first diagram - current ...
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### What's the relation between broken time-reversal symmetry and spontaneous internal magnetic in superconductor?

"For states with broken TRS, a spontaneous internal magnetic field can appear below $T_c$." How to understand?
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### How do you calculate the error propagation in a Helmholtz coil?

I'm having some trouble with the error propagation expression in a Helmholtz-coil. Specifically $\frac{\frac{∂B}{∂R}}{B}$. If anyone could help, I'd be really grateful. The formula used is B(x) = \...
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### Force exerted on an uncharged particle in a uniform magnetic field?

I'm struggling to understand how to calculate the force exerted on an uncharged particle in a magnetic field. Consider the following setup: a ball of ferromagnetic iron weighing 1kg is placed in a ...
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### Induce electric field in an incomplete circular conducting loop

I was solving a numerical example(image1) of 'Griffiths book of electrodynamics' And in this solution it is given that if there is a changing magnetic field is there there would be induce induce ...
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### Weakening of magnet effect

Does the presence of a neodymium magnet around (or in the proximity) of the iron (no connection and At a distance of 1 millimeter ) lead to the gradual weakening of magnet effect? What if it connects?
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### Why does changing the flux induces a voltage and thus a current

I have seen similiar Questions being asked for example Why Does Change of Magnetic Flux Induce an emf? However i am not satisfied with the answers. It seems to me that this Question is usually ...
648 views

### How resistance in coils affects the damping of oscillations of a magnet through them

I performed an experiment where I connected a magnet to the end of a spring with the north side on the bottom. The magnet at the tip of the coil was aligned to pass through a column of coils of about ...
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### Magnetic field in a toroid

How does the magnetic field becomes 0 outside a toroid? Also how can we explain it with magnetic field lines?
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### Where are current flowing in a permanent magnet?

We know that moving charges produce magnetic fields if then all elements have electron with some non zero angular momentum so all substances must be magnetic to some extend.But this does not happen. ...
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### What is the relationship between the Ising model and a magnet's corresponding magnetic field at varying temperatures?

I understand that ferromagnetism occurs when all the spins in a magnet are aligned, leading to the magnetic vector field that we are familiar with. What happens qualitatively to the magnetic field as ...
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### Cause of induced EMF in a loop

Len'z law states that the change of magnetic field in a loop of wire produced current in a wire as the magnetic field in and out the loop.Although it just true experimentally, but i) What happened ...
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### 2 Possible Radii for Circular Motion?

I was solving a task dealing with electricity/magnetism, in which a charged, dimensionless particle was simultaneously affected by a uniform magnetic field and the electric field emitted by a fixed/...
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### Increase in measurement of magnetic field lines due to increase in current

My teacher told that the number of magnetic fields in a current carrying conductor increases as the current flow increases. So, does the length between two magnetic field lines also increase if there ...
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### A different answer with Ampere's Law

Consider a circular loop of radius r and a wire of finite length which lies along the axis of the loop. Current I flows through the wire and. I am trying to to find $\int \vec B \bullet d\vec l$ over ...
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### How was the first magnet made?

An iron ore (natural magnet) in the earth's crust gets magnetized due to another magnet near it which aligns all its domains in one direction. We mine up that ore and use it to make other magnets (...
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### How to convert dBm/MHz to dBm?

I wonder if we can convert dBm/MHz (eirp) to dBm? For example: What is the equivalent of -30 dBm/50MHz as dBm? Edit 1: I wonder if power spectral density (dBm/MHz) can be expressed in dBm. In EN 302 ...
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### Why does magnetism penetrate all known materials

Does there exist a reason without complex mathematical descriptions that can account for the fact that there are no known materials that magnetism does not penetrate. I found a reference to Maxwell's ...
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### What are the fields produced around a current carrying conductor?

If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged (...
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### Magnetic field and frame of reference [closed]

A charged particle moves with a velocity near a wire carrying an electric current,and suppose I see the particle from a frame moving with same velocity in the same direction . I will see the charge at ...
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### Is levitation possible through this apparatus?

If we had two rigid sheets which were exactly identical and we had the magnets on it as shown in the figure, then would the top sheet float above the bottom, which is fixed on a rigid surface. The ...
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### Why aren't we (humans) affected from magnetic field?

From what I understand humans has a capacitance and are able to store charge, and we also have a velocity, we know that the magnetic force is $\vec{F}=q\vec{v}\times \vec{B}$. I assume while we ...
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### Can this magnet setup act on charges similarly to a quadrupole magnetic field?

As the title indicates, could magnets set up like this work to focus charged particles similarly to if they were passing through a quadrupole magnetic field? Obviously the charge and direction a ...
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### Why doesn’t Direct Current produce electromagnetic waves

So electric fields are produced due to presence of charged particles and magnetic fields are produced due to motion of charged particles. In DC circuits, a current-carrying wire involves the motion of ...
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### Why is Lorentz force frame independent?

Recently I started studying Magnetics and I came across a statement in my book which confused me.It read: Magnetic force is frame dependent, Electric force is frame dependent but lorentz force is ...
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### Area chosen for magnetic flux

Let us say we have a square frame of side $a$. We project a magnetic field $B$ perpendicular to the plane of the frame to only one half of the frame. So in this case to find the induced emf what ...
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### Magnetic field inside a ferromagnetic material

Let us suppose there is a block of a ferromagnetic material inside a very long ideal solenoid. We know that the magnetic field lines inside are always in a straight line which will be perpendicular to ...
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### 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 ...