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 [tag:magnetism], as questions about the phenomenon & theory of magnetism do not necessarily involve the discussion of fields.

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46 views

Nuclear relaxation time in absence of a magnetic field

It seems that after reading about how MRI scans work, and it appears that I had a misconception of what T1 relaxation times mean. From what I think I understand now, the T1 relaxation time refers to ...
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2answers
35 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 (...
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1answer
210 views

Electromagnetic induction in varying current

I know about Faraday's Law and how it states that an electric field will be produced if it will sense a change in magnetic flux that there are other sources of electric field except for an electric ...
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1answer
34 views

Potential drop across inductors in DC circuits

The potential drop across an inductor is equal to $L(di/dt)$ where $L$ is inductance coefficient. But according to this in a DC circuit there should be no potential drop across the inductor (because $...
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2answers
45 views

Do magnetic field lines indicate how a mangetic field will act on an “idealized” test magnetic north monopole?

We imagine an electric field and a magnetic field as vector fields. When we are introduced to a static electric field, we usually picture it as an infinite number of vectors (magnitude,direction) in ...
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2answers
148 views

H field Vs B Field inside a magnet

I was studying electromagnetism and was going the basic definition and trying to understand their importance. I could not figure the difference between The H- Field and B- Field at first. So I ...
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3answers
6k views

Can metal rods detect underground wires?

Until not long ago, I was working in the drilling and infrastructure business. Some people I was working with used metal rods as a "quick and dirty" method of detecting underground wiring, before ...
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2answers
63 views

Permanent magnet attraction from Maxwell's equations / Lorentz force [duplicate]

Edit: My question is different because I am not asking how permanent magnets come about. Rather, I am asking why (taking permanent magnets as a given) they attract or repel each other. I.e. What ...
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4answers
10k views

Is there any material that is NOT conductive and IS magnetically attractive?

Is there any material which is NOT conductive and IS magnetically attractive? I am in need of a material which I can shape and use within a machine. It must be very attracted to magnets similarly to ...
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1answer
27 views

Magnetic Detection of Magnetite

I have a tool with a very thin and faded coating of what seems to be magnetite black oxide ($\mathrm{Fe_3O_4}$), I’m trying to see if this coating is magnetite, while a chemical test is possible, a ...
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3answers
522 views

Magnetic flux inducing EMF

Faraday's law states that a coil with a larger magnetic flux will have a larger induced EMF, is this true or false? The induced emf is directly proportional to the rate of change of magnetic flux ...
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1answer
343 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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2answers
135 views

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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24 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 ...
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1answer
60 views

Can we calculate the magnetic field of a permanent magnet?

We are always introduced to magnets by pictures illustrating a parallepiped magnet, a horseshoe magnet, etc... Anyway the first time we actually calculate a magnetic field is for eelectromagnets. ...
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1answer
47 views

Understanding of Gauss law using vector fields

I was going through the conventions and terminologies followed to describe the magnetic interactions. I understood that the field lines are just a simpler representation of the magnetic interaction ...
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4answers
121 views

Electromagnetic waves according to Maxwell

If a variable Electric field creates a variable magnetic field and VICE VERSA (according to Maxwell's equations), then why don't we enter a loop where E vector and B vector keep creating one another ...
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1answer
20 views

Motion of particle in uniform magnetic field with friction propositional to velocity [closed]

A positively charged particlewith charge "q" is at $ (0,0,0)$.There is a uniform magnetic field $ \vec B= -B \hat k$. The particle is given velocity $\vec u= u \hat i$. A resistive friction acts on ...
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2answers
140 views

Induction heating

An induction cooktop has a high frequency power source that is applied to a coil. I was wondering if you could take the high frequency electronics on a cooktop and instead of a coil take a 30 or 90 ...
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1answer
73 views

Newton's third law in magnetic in magnetic fields

Say I have a charged particle moving through a magnetic field perpendicular to it. It will experience a force, but according to Newton third law Every force has an equal and opposite reaction. So ...
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1answer
57 views

Does protons moving parallel to each other exert magnetics force

If two protons are moving parallel to each other in same direction with equal velocities then do they exert magnetic force on each other.? As protons are moving they should produce magnetic field and ...
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1answer
214 views

Varying magnetic field creates varying electric field. Does constant magnetic field creates a constant electric field?

Varying magnetic field creates varying electric field. Does constant magnetic field creates a constant electric field? If yes, an simple wire(like on picture, for example) with DC power will attractes\...
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2answers
159 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 ...
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2answers
116 views

Why doesn't a magnetic field accelerate moving charges?

As a magnetic field of intensity, $\mathbf{B}$ applies a force of $\mathbf{F}= q\mathbf{v} \times \mathbf{B}$ on a charge $q$ moving with velocity $\mathbf{v}$, this force $\mathbf{F}$ should be ...
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2answers
33 views

What do you see when you are inside a transparent conducting material?

Lets say that there exists a transparent conducting material. Lets carve a cavity in the meat of the conductor big enough for a person to stay in. There exists an external electric field. But, We ...
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1answer
184 views

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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3answers
334 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 ...
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2answers
144 views

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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1answer
91 views

Why the geomagnetic field become stronger when solar wind is stronger?

The following description is from the webpage of Niels Bohr Institue's Former Centre for Ice and Climate The Earth reacts to the solar wind by increasing the strength of the shielding magnetic ...
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0answers
16 views

Guided propagation in transmission lines

Can you help me on understanding why we may say this transmission line the propagation is guided and there is not any radiation? It is a 2-conductors transmission line, in which the conductors are ...
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2answers
263 views

Need help in finding error in calculation to find Earth's magnetic field strength using Galvanometer

I am working on a experiment on finding the Earth's magnetic field strength. Using a Galvanometer and a constant power source of 5.1V and slowly adjusting the resistance, I was able to find the ...
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0answers
9 views

Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models?

The title itself explains what is my question. Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models?
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41 views

Is the flow of charges in inductor though electric field zero?

How electric field inside the wire of an inductor is zero (i.e. material of which loop is made — note material is assumed to be a superconductor), then how electrons flow in an inductor if electric ...
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1answer
51 views

Is Meissner effect really caused by expulsion of magnetic flux?

The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state. This is the explanation by mainstream physics. But the experiments ...
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2answers
5k views

Why is a steel ball-bearing repelled from a magnet towards a piece of unmagnetised steel?

At the risk of sounding like one of the Insane Clown Posse, I was watching this video of the late Eric Laithwaite discussing magnetism: Eric Laithwaite, Circle of Magnetism (1968) (the relevant ...
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0answers
32 views

MHD pump liquid metal flow speed

a rather simple question, are there any studies or some information about the flow speed of liquid metal inside a tube? My setup is basically a 50cm diameter circular tube (could be another diameter) ...
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2answers
42 views

Effect on radio waves from forcing two magnets together

Wrapping up a cellphone in aluminium foil or putting it inside a microwave will block out all signals. Somebody suggested to me that forcing two very powerful neodym magnets against each other and ...
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1answer
62 views

Nature of induced emf in Faraday's law

When there is a battery in a simple circuit loop, for instance, there is a real low potential terminal and a high potential terminal , the battery does work on charges and delivers them at high ...
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1answer
38 views

Biot - Savart Law and time - variable current [duplicate]

Is the Biot Savart law valid also with currents which are functions of time (for instance a sine wave)?
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1answer
33 views

Helmholtz equation and sources

it is known that starting from the Maxwell equations it is possible to get the following Helmholtz equations: In time domain it corresponds to a sinusoidal EM field, according to the wave equation: ...
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1answer
154 views

The direction of the induced electric field

Recently I got stuck witht the following problem. Imagine we have uniform a magnetic field which induction points upwards. The fields strength is steadily decreasing. If we put an iron coil ...
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1answer
39 views

Magnetic field of rotating wire

I was doing some questions on the magnetic field when a charged body is rotated on its general axis, but I had a doubt that what if it's not the general axis but somewhere else. Like, for example, ...
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2answers
62 views

Where is the extra momentum? [closed]

The question is A particle of charge q enters the region of uniform magnetic field B (pointing into the page). The field deflects the particle a distance d above the original line of flight, ...
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2answers
167 views

Does accelerating magnet emit radiation?

Just like accelerating charge produces emits radiation, does an accelerating magnet emit electromagnetic radiation?
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1answer
27 views

Combining axial and toroidal flux

Is it possible to combine axial and toroidal flux , or any two fluxes that share a common core or part of a core? Imagine I have a toroidal flux through a toroid like core seen in the picture below, ...
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7answers
16k views

Why is there no magnetic field around a wire connected to electricity at home?

Is it true that an electric current that flows through a conductor creates a magnetic field around the conductor? If yes, then why doesn't the magnetic sensor of my mobile device react in any way to ...
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1answer
30 views

How can diamagnetism levitate anything?

From the explanation of diamagnetism that I was given, the electrons when exposed to a changing magnetic field will change their spin in accordance to Lenz's law. This will induce an opposing magnetic ...
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2answers
85 views

Complex vectors: Electric and Magnetic Fields

I have a doubt about the physical meaning of the complex representation of electric and magnetic fields. Let's consider an electromagnetic wave, in which both electric and magnetic fields propagate ...
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3answers
105 views

Is there a better definition of magnetic field than this?

It may seem a trivial question but the definition of the magnetic field in everyday books is misleading. "It is the region or area around a magnetic material in which its magnetic force can be felt." ...
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0answers
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Elliptical precession of magnetic moments due to external magnetic field

I have a magnet lying in the XY plane which happens to have an in plane Anistropy along +X. If I apply a field along +Z, the magnet, if initialized not along +Z, is expected to precess about +Z. ...