# Tagged Questions

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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### Quantization of the Hamiltonian of a particle in a uniform magnetic field

If a particle of mass $m$ and charge $q$ is subject to a uniform magnetic field and if we have a vector potential $\mathbf{A}$ then we know that classically the dynamics of the particle will be ...
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### What is a simple model to find the jump height for the Thomson's Jumping Ring experiment?

I'm trying to devise a basic formula that could give a rough estimate for the jump height reached in the Thomson's Jumping Ring experiment, as detailed here. However, it's pretty difficult as most ...
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### Magnetization of the toroid

As far as I understand, bodies are magnetized by orienting electron spinning within the atoms. Once placed into magnetic fields, they align rotation so that they produce magnetic field in the same ...
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### Motion of current carrying rectangular coil in magnetic field

a current carrying rectangular coil is placed in a uniform magnetic field as the plane of coil is parallel to the field at the beginning . assume that there is no restoring torque and no friction. i ...
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### Current loop and direction ambiguity of the magnetic moment

Consider a circular loop in the XY-plane which carries a current $I$. Then it behaves as a magnetic dipole with moment $\textbf{m}=I\int d\textbf{S}$ where $\int d\textbf{S}$ is the area of the loop ...
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### Net magnetic field at a point

Given 5 wires ( $w_0, w_1,w_2,w_3,w_4$) all separated equally by a distance ($r$) from one another like this diagram: Applied a voltage two each wire individually and current flows like so: Also,...
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### Why does the Emf generated by a magnet going through rings of coil generate a sinusoidal curve of Emf vs time?

I am having trouble writing the reason for the part of the curve to cut the x axis at Emf = 0 and when reason for curve to form max and min peaks.
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### Interaction between magnetic moments and magnetic field

Consider a particle with a magnetic moment $\vec{m}$. For simplicity, suppose that this particle is a circle in the plane $xy$ which can rotate around its center of mass along the $z$ axis. If this ...
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### Why do magnetic field lines converge where the strength is strongest?

In most of the sites, they just say that "to determine the strength of the magnetic field, one must look at how many lines are present at a particular location." But my question is why? Why is this ...
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### Why should you be careful when you use a Hall effect probe to measure magnetic field?

Question: Why must you be careful with orientation when you use the hall effect probe to measure magnetic field? Background: In a recent Physics 2 lab, we used a magnetic field sensor which ...
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### Magnetic Fields and their strength

1) Does a larger magnetic field make a magnet stronger or extend the range (space) in which it can influence objects? 2) What makes a magnet 'stronger' (have a larger attractive pull)?
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### Magnetic field of multiple loop turns?

Given this equation to calculate the magnitude of the magnetic field: $B = \mu_0 \frac{N }{l} I .$ Where $\frac{N }{l}$ is the number of turns per unit length. $I$ is the current, $\mu_0$ ...
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### Magnetization of the source due to a stronger induced magnetic field?

Considering this classical diagram: From the top view, we can see a current carrying wire( flow of current is into the page) while an exterior magnetic field($B$) is applied perpendicular to it, ...
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### Calculating magnetic field strength in gap of tapered toroidal electromagnet

Consider a toroidal electromagnet filled with a magnetic material of large permeability $\mu$. The torus contains a small vacuum gap of length $h$. Over most of its length the torus has a circular ...
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### Magnetically shielding an actuator

We need to magnetically shield a solenoid that activates this valve (shown below) Just slipping a mild steel cap over the end does not do the job, nor appears to have any screening effect at all. ...
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### It's not the size of your magnet?

Growing up I've seen magnets on the fridge to the cows stomach and the latest that I know of, neodymium. On a molecular level what makes some magnetic material stronger and last longer than others?
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### How does High mu metal block a magnetic field?

Fran De Aquino suggested VLF currents would trigger a mass shift in high mu metal. But my question is how is a magnetic field actually blocked in high permeability metal?
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### Is it possible to strip the magnetic, or electric field from a photon?

A photon is made up of a magnetic part and an electric part, but we can see the existence of these fields without the other one so I would like to know if it is possible to somehow separate one field ...
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### How can the energy of a spinning black hole be converted into magnetic field?

I've read about the Blandford-Znajek process, and what I understood is that the black hole is treated as if it were a conducting sphere spinning rapidly with an accretion disk around it, and the ...
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### What prevents this magnetic perpetual motion device from working? [closed]

Two days ago, I thought of this device, which may seem to rotate indefinitely(in all 3 directions). I have two questions. Is this perpetual motion machine already known? If it is, could you please ...
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### Questions regarding magnetic fields and magnetic field lines

I went through certain statements regarding magnetic fields and M.G lines which I am not able to understand. First doubt: Why do magnetic field lines form closed curves? I went through some ...
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### Magnetic field of rotating charged insulating loop

A charged insulated square loop of side length $a$ is rotated about an axis perpendicular to its plane. What is the ratio of the magnetic field in its centre to the magnetic field of a rotating ...
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### How to Calculate the force between two different cylindrical magnets?

What happens to the formula when the two magnets aren't identical in height? One is a tiny neodymium magnet and the other is a longer electromagnet. Both are the same width but not height. Thank you
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### Which procedure is correct? [closed]

A problem is given in my textbook pg.no-191 as Example 5.10 A solenoid has a core of a material with relative permeability $\mu_r=400$. The windings of the solenoid are insulated from the core and ...
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### Which quantity is independent of others? [closed]

My textbook quotes that:pg.no-190 The three quantities $X,\, U_r$ and $U$ are interrelated and only one of them is independent. Given one, the other two may be easily determined. Where ...
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### Why do all magnetic field of a bar magnet do not start and end only at pole?

Iam very confused that why not all field lines emanate out of a pole? Why few field lines emanate and in middle of a bar magnet as shown in the following figure:
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### What is the direction of magnetic lines of force inside a bar magnet? [closed]

So basically , we all know the direction outside the magnet its from NORTH to SOUTH. but what i don't understand is that what is the direction inside is it the same ??
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### Inductor circuit

Consider a inductor circuit with an inductor connected to a DC battery and a switch. Initially the switch is open. At time $t=0$ the switch is closed. What will happen to the inductor just after the ...
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### Stabilizing a shaft with only one electromagnet

I have recently come across Earnshaw's theorem in my research which states that it is not possible to stabilize an object using only static permanent magnets. I understand that and it makes sense to ...
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### How to get speed of a train without using GPS

How can I measure instantaneous speed of a train in which I am travelling without using GPS/location services? The train can start underground or can start from ground level (where GPS is available) ...
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### Creating a Magnetic Monopole through a torus [duplicate]

Could you create a magnet in shape of a hollow torus and magnetize it so that the interior is south and the exterior is north in order for it to act as a monopole? Is that possible? Thanks
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### Does the magnetic flux spin in the same direction when the electric field is growing and collapsing?

I have three concentric iron pipes, stacked inside each other. It looks like a bulls-eye when viewed from above. To the innermost and outermost pipes I have connected a battery through a switch. ...
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### Which conditions need to be fulfilled for a FODO cell to provide focusing in both planes?

I often come across the claim that a FODO cell can provide focusing in both planes so long as said cells are appropriately configured. I have never come across any elaboration of what this "...
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### How does the electrons' magnetic dipole moment get influenced when electrons are moving through a magnetic field?

How does the electrons' magnetic dipole moment get influenced when electrons are moving through a magnetic field? How does the electrons' intrinsic spin influence the direction of the electrons' ...
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### Magnetic Field in parallel plate capacitor [closed]

A parallel plate capacitor of area 60cm^2 and separation 3mm is charged initially at 90 micro coulomb. If the medium between the plates get slightly conducting and the plate loses charge initially at ...
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### Can a magnetic field affect the streaming current in high velocity water?

When you flow water at high velocity through a pipe you get a streaming current close to the pipe surface. If you were to then apply a large magnetic field across this pipe (perpendicular to the flow/...
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### The Strength of the Tangential and Radial Components of a Dipole Magnetic Field

I am following along well several textbooks (Geophysics) that helps me understand the in-depth physics behind the magnetic field of a dipole magnet. I understand that the basic magnetic potential (...
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### Can we magnetize magnetic tape / disk with constant magnetic field?

I am remember that have read in childhood, that tape recorders require alternating magnetic field to work. Is this true? Is there any difference between magnetizing by constant and alternating ...