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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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 ...
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2answers
162 views

What determines the magnitude of force of an electromagnet?

Let's assume that there is an electromagnet with $B = 1 Tesla$ , what is the magnitude of the force it could generate on other dipoles equal to it's surface area? Can the magnitude of force (in ...
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29 views

Can current be stopped using magnetic field?

Is it possible to stop a current "running" through wire only by using a magnetic field around the wire?
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33 views

Magnetic field re-routing

Can a magnetic field be directed in a particular direction, that is re-route it, such that the magnetic field comes out in only one direction?
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1answer
1k views

Why is the magnetic field stronger at the edges of a bar magnet?

I have been performing an experiment at school in which I test the force on an iron surface from the magnetic field of an electromagnet. The electromagnet has a rectangular iron core. The theory ...
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37 views

Magnetic field on axis of solenoid

So first I'd like to say that I have asked similar questions to this one. However, all the answers involve a level of calculus that I do not yet know. (Still on limits, going to spend the rest of ...
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3answers
150 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
51 views

What are the interpretations of ampere's circuital law for a single moving electron?

I understand from Ampere's circuital law that when a current passes though any open surface with a boundary (a circular boundary, for simplicity), then limit of summation of the scalar products of ...
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0answers
28 views

Quantity of force between two magnets

I have compiled data detailing a magnetic field. If I assume a duplicate magnet is set up across from it, how can I calculate the repulsive force between them?
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2answers
196 views

Currents induced by rotation of a coil about magnetic field lines

If the coil on the left is rotated about the magnetic field lines, will there be an induced current? I know that the flux concerns only the component of the magnetic field perpendicular to the ...
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1answer
152 views

magnetic field of a rotating ring magnet

Can the magnetic field of a rotating ring magnet induce current in a conductor? Is there a flux linkage between magnetic field of a rotating ring magnet and a conductor?
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1answer
385 views

Coercivity of a ferromagnetic material?

I understand that coercivity is the field/force required to demagnetize/magnetize a ferromagnetic material. What if we had two opposite magnetic fields of different strengths values H acting on the ...
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1answer
162 views

Computing energy loss for a hysteresis curve

Let a hysteresis loop be as shown in the figure, with $B_0$ the applied external field due to a current $I$ in a toroid, and $B_M$ the additional field due to the ferromagnetic material. Hence we ...
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1answer
134 views

Magnetic field of a static disk magnet

I have a magnetic disk (Radius R, height h) that creates magnetic field lines (axisymmetrical). I simulated the field lines, exported the data and am now trying to fit a function into the data to have ...
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2answers
109 views

How can magnetic fields have energy and yet be unable to do work with that energy? [duplicate]

Magnetic fields can't do work. However, we use the following equation to describe the energy density of a magnetic field. $u = \frac{B^2}{2\mu_0}$ The term energy density suggests that the magnetic ...
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1answer
106 views

Repelling a weak permanent magnet with an electromagnet

I have a question about magnetic repulsion. Suppose I have a permanent magnet (axially magnetized) placed on top of the iron core of an electromagnet. I want to switch on the elctromagnet to repel the ...
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2answers
209 views

Why is there no induced electric field in the experiment (Faraday's Law)

Below are three circuit diagrams for each of Faraday's experiments that allowed Faraday to come up with Faraday's Law. In Griffiths' Introduction to Electrodynamics Griffiths states (on page 302 of ...
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24 views

Magnetic field due to current carrying sheet

I have 2 infinite plates (x direction) with the width of A (y direction) and the distance between them is d (z direction). The current density is J on the first plate and -J on the second (the ...
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4answers
92 views

How does an inductor store magnetic energy?

I am trying to figure out what the potential energy of an inductor with a current really means. In a capacitor, the energy stored works like this: if you let the plates attract each other, before ...
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0answers
54 views

How it is predicted, that a moving charge has to have a magnetic field?

This question appears after this comment: Even electric charges without intrinsic magnetic dipoles moments produce magnetic fields when they move. My respons: All electric charges (electron, ...
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2answers
455 views

Torque per unit length on infinite rotating charged cylinder

For homework I have the following question, but I am stuck on finding the torque on the cylinder. An infinite cylinder of radius $R$ carries a uniform surface charge $\sigma$. We start rotating the ...
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1answer
115 views

Constant magnetic field attenuation by µ-metal (mu-metal)

I am interested in the magnetic field attenuation by µ-metal. Specifically shielding from earth's magnetic field $\boldsymbol{H}_E$ through closed cylindrical layers of such a metal, yielding an ...
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0answers
2k views

How to calculate magnetic pole strength?

I have 2 magnets. I need to know the force between them. In a previous Phys.SE question, conclusion was: we need to use a dipole-dipole interaction equation, which included m, which the magnetic ...
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1answer
34 views

If we were to observe a cluster of planets from a star's magnetic north, which direction would they appear to orbit? Clockwise or counter clockwise?

I have a question, and it's been a topic of great discussion amongst my peers. If we look at galaxies or clusters of planets around stars, they appear to be moving both clockwise and counter ...
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1answer
38 views

Force of electromagnet on a wire [closed]

I'm trying to produce an equation for the force produced by an electromagnet on a wire. I'm very aware I don't know any vector calculus but I think as it's the special case (Perpendicular) I can just ...
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0answers
18 views

Off-axial Field of Finite Solenoid

Regarding the computation of the off-axial field of a finite solenoid: The Radial and Z components of the off-axial magnetic field of a solenoid are given as: \begin{align} B_r &= \frac{\mu ...
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2answers
57 views

Concept of a Magnetic Field

I was reading a physics book by some author and I got a little too confused with the explanation he stated about magnetic fields. A magnetic field is a field of force produced by current-carrying ...
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1answer
46 views

Fringing effect of electric current

We know the what is the fringing effect of electric field in capacitor, of magnetic field in some in some solenoid or magnetic field in through joint of some metal. But is there is something similar ...
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3answers
539 views

The magnetic field of a magnetic monopole

Let us define the magnetic field $$\vec{B} = g\frac{\vec{r}}{r^3}$$ for some constant $g$. How can we show that the divergence of this field correspond to the charge distribution of a single magnetic ...
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0answers
47 views

Adding Magnetic Fields?

Ok, so we all know that the strength of a magnetic field can be increased if a wire with current flowing through it is surrounding the magnet. Because the current flowing through the wire is making a ...
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0answers
28 views

A magnet floating due to Meissner effect

If a magnet is floating due to the Meissner effect, can the magnet rotate freely under influence of external field in spite of the presence of north and south pole in it ?
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0answers
21 views

surface current density

Surface current density, K is defined as: K = σv where σ is surface charge density and v is velocity. Given a uniformly charged spherical shell with radius R, spinning at constant angular velocity ω, ...
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45 views

Regarding Ampere's Circuital Law

If I am to show that Ampere's Circuital law holds true for any arbitrary closed loop in a plane normal to the straight wire, with its validity already established for the closed loop being a circle of ...
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0answers
57 views

$E$-field from changing current in straight wire

A very long insulated wire oriented along the $z$ axis of a cylindrical coordinate system is carrying current that is defined by the following function: $$I(t) =Io + k⋅t$$ (current increases linearly ...
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1answer
18 views

$H$ field from corresponding $E$ field (antenna)

The $E$ field at $kr >> 1$ due to a short dipole oriented in the $z$-direction and located at the origin is: $$E_0 = \frac{10^3e^{-jkr}}{r}\sin\theta\space\space(V/m)$$ Can I just solve for the ...
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1answer
35 views

Dependence of Hall coefficient on temperature in copper

As part of a project on the Hall Effect in metals, we would like to find out whether the Hall Coefficient of copper depends on its temperature, and if so how. We passed a current I through a copper ...
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0answers
25 views

Conductors - force needed to maintain a constant velocity

There runs a current $I_0$ through a straight and long conductor. Two more conductors are placed parallel to it in a plane with distances a and b respectively. The resistance of the connection is ...
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2answers
85 views

Magnet dimensions for 3-phase permanent generator

I'm making a 3-phase permenant generator. According to Faraday's law, the emf produced is negative number of turns times the change in magnetic flux over the change in time. If it is only the CHANGE ...
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2answers
92 views

What is the secret of this perpetual motion machine with neodimimum magnets?

The following device is apparently based on magnetic forces only and has no visible energy source: Where is it's energy source? Full video: http://www.youtube.com/watch?v=eA0b-8pqUCk UPDATE One ...
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2answers
66 views

Particle beam in infinite magnetic field

In a physics exam at university I had the following problem: A proton-deuteron beam is accelerated by a $\Delta V = 10^7\,\mathrm{V}$ difference of potential. At some point, the particles enter ...
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2answers
155 views

Ion Optics: Electric and Magnetic field. A comparison with Light Optics

When we compare ion optics with light optics, normally we consider electric field. For example Snell's law. $n_1\sin\theta_1$=$n_2\sin\theta_2$. When an electron move from one electric potential to ...
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1answer
56 views

Is the Biot Savart Law applicable only for continuous currents?

There is a widely known formula for the magnetic field due to a moving charged particle. $$\frac{\mu_0}{4\pi} q \frac{\vec{v}\times\vec{r}}{r^3} $$ The usual derivation is as follows. $$ dB = ...
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4answers
327 views

Can current be induced in a superconductor?

Moving a magnet close to a conductor induces a current. If it consists of a superconducting material with resistance $R=0$, then my textbook says: Then the induced current will continue to flow ...
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0answers
29 views

Magnetic levitation project

For the past four years, I have been working on a project that will allow permanent magnets to levitate stably above a magnetic surface. So far I have tested my first theory which was to see if ...
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1answer
28 views

why induced emf in primary coil is only caused from self inductance but not mutual inductace

A is primary coil and C is secondary coil A is connect to a battery while there is no source connected to C When the current in A varies with rate $\frac{di_0}{dt}$ there is induced emf in B that ...
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1answer
38 views

Simple question with magnetic fields

On my test of today was the following question: "an aluminium block moves with a constant speed over a road, ahead of it is a magnetic field. Does the speed change when it enters the magnetic ...
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0answers
21 views

Quantum Locking Inverted

I have recently been investigating the phenomenon known as "quantum locking". I have many questions about the engineering aspects of this phenomenon such as what range it operates, what shapes can be ...
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1answer
34 views

Electricity on magnetic powder

I had the idea of, what if you ground up some magnets into a fine powder, what would happen with the powered, and how would it act? After some google searches, it seems that this isn't done very ...
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0answers
13 views

Analytical Calculations For a Stable Electret in Motion in Interplanetary Space. Determining the magnetic field

We know that a charging capacitor has, associated with the increasing E-field, a magnetic field. Now please consider the case of a very strong dipole or E field produced in an electret. Let us say ...
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0answers
42 views

Torque on a wire loop from straight wire [closed]

I need to show that the torque on this wire loop is $$N = \frac{\mu_0}{\pi} 2abdII' \frac{(b^2+d^2)\sin(\theta)}{b^4+d^4-2b^2d^2\cos(2\theta)}$$ The where $\theta$, is the angle between the loop ...