Magnetic Definition and 1000 Threads

Hi all, In textbooks and all other places they are saying that in principle magnetic monopoles can exist but yet have not been found (isolated). My pain increases further when I see a theoretical physicst say statements like, "We do not know of any theoretical reason why magnetic monopoles...

I need to find the magnetic field of a permanently magnetized cylidner: In calculating the magnetic field, i find that it should be $M_{0} \mu / 2$ and $H = M_{0} / 2$ inside. I just want to make sure that i understand the concepts in this type of problems. Since $M = H \chi (1)$, does this...

First I wrote in ##S'##, by using Gauss theorem $$ \int_{\Sigma} \underline E' \cdot \hat n d\Sigma = \frac Q {\varepsilon_0} \rightarrow E'(r)2\pi rH=\frac{\lambda'H}{\varepsilon_0} $$ $$ \underline E'(\underline r)=\frac{\lambda'}{2\pi\varepsilon_0r}\hat r $$ Its components are...

I need to calculate the magnetic field generated by a static sphere at its center. On the surface of the sphere flows a constant current ##K \hat \phi##. Now, my guess was that the field produced would be equal to the field produced by a lot of rings, that is, i will split the sphere in a lot...

When a charged particle moves in a magnetic field, the magnetic field will not work. But when a nail flying over a permanent magnet is attracted by the magnet, the magnet does work on the nail. Can anybody explain why this is so?

From what I understand, electrons are negatively charged, however, I have recently come to learn that electrons also have a spin which creates a magnetic field around each electron. I don't understand how the electron can be a negative monopole, yet have a completely independent magnetic field...

Hi, I have a toroid of a soft magnetic material (any). I wind the complete toroid with single turn coils and connect all their terminals in parallel. Then I wind a second layer of single turn coils on the previous layer and so on. I want to calculate the equivalent inductance L. I calculate it...

This is not a homework problem, I want to calculate the equation of the magnetic field intensity from the 3 phase currents separated by 120Degrees. The 3 currents are ##I_{{aa}^{'}} = I_M\sin \omega t ; -> eq1 \ I_{{bb}^{'}} = I_M\sin(\omega t - 120); -> eq2\ I_{{cc}^{'}} = I_M\sin(\omega t...

Consider a region where a 25-volt-per-meter electric field and a 15-millitesla magnetic field exist and are along the same direction. If the electron is in the said region, is moving at a direction 20 degrees counter-clockwise from the direction of the magnetic field, and is experiencing a total...

Hi guys. I work with statistichal mechanics, applying classical spin models, as Ising model. I'm trying a collaboration with a colleague that works with first principle calculations. Does anyone know how to calculate the exchange interaction and anisotropic constant (of the Blume-Capel model)...

I'm given an ultra-high energy cosmic ray with energy 10^20 eV. It is coming from a source 10 Mpc away with an extragalactic magnetic field with strength B = 10^-9 G. I am to determine the maximum angular deflection of this cosmic ray, so it hits Earth. I don't have an attempt of the solution...

Summary:: Can a moving object cause disruptions in a magnetic field that could be detectable? Hello, I was hoping someone could assist me on a query I have regarding disruptions in a magnetic field. For some context, I am creating a science fiction story which features a non-humanoid alien...

Hi, I tried to solve this exercise but I'm not sure about the process. First of all, I imposed that "K = E": so that "v = √ ( (2q ∆V)/m))" then I replaced in "r = m v / (| q |B)", v with "√ ( (2q ∆V)/m))", and found out that R = (2√(2)) r. Then for the second point, I imposed Lorenz Force...

Hi, I was practicing some problems on the magnetic field and the electromotive force, when I got stuck on these two exercises. Could you help me figure out how to proceed? In the first problem, I tried to find the magnetic field flux by multiplying the induced current for ∆t and R. Should I now...

Why is the energy of a circuit placed in a magnetic field at infinity zero?

In QFT where the electromagnetic field is mediated by virtual photons, is it possible to describe the larmor precession of an electron as a series of emission and absorption of virtual photons? how does the spin angular momentum "evolve" over a series of events? This feels like a challenging...

hi every one what is the amount of orbital magnetic dipole moment of proton? this different with the intrinsic magnetic.

Here on Earth there are three major geodynamos that generate the magnetic field. My question is about how they interact. My guess that while the axis of rotation of each field is different, the fields they generate tend to align. My further guess is that they do so only partially so that in...

I am only asking about part (b)(i) and (b)(ii). Below is the explanation for (b)(i). What is going on in the above? I understand up till the 3rd line, about the left/right hand circular motion. What is the "upward motion" the solution mentioned? Is it suggesting that ions are moving...

Hello! Lately I've been experimenting with the ways an electromagnet effects a Rare Earth magnet. The electromagnet we used was taken from a vibrator massager, probably 50s vintage. The resistance of the coil is 96 ohms and consumes about 1.25 amps when operated on 120 volts AC. When the...

Hello all!, first post here we go! I was hoping someone could answer a question for me because I can’t find the answer online. Or maybe point me to a magnetic field’s for dummies website.. I’ve been playing with a neodymium magnet shaped like a coin for a few days (yes easily occupied) and...

I want to perform an experiment to show that magnetic fields can control plasma. (Can even be a slight repulsion) Please Suggest one. I have no idea where I can obtain plasma - I have access to candle flame (though it's not a proper plasma) & fluorescent lights. I have a permanent magnet (not a...

The current density between the plates is J = 1 A/m2. So, I have to calculate first the magnetic energy in the whole space. Out of the sheets, there is no current, so the magnetic energy would be 0 in that places. Hence, U = J(1/2) \int_{inside the plates}A(r)dr, where A(r) is the vector...

For my end-of-semester project, I was tasked to investigate an aspect of magnetism/magnetic materials, to do some literature review on the topic, and code a mathematical model and display my results graphically. I couldn't find anything I wanted to do, so I asked the professor to assign me a...

So what I'm not sure on, is calculating the matrix elements for part (iii) with Pauli spinors and Pauli matrices, and then finding the form of the corresponding states. As I don't see how using the hint helps. The following is using the eigenvalues of the spin-operators. Provided what I...

For a solenoid, magnetic field at the centre = ##\mu_0nI##. I see the argument on why at the opening at the ends of the solenoid, the B-field is ##\frac12\mu_0nI##. Apparently, B-field is ##\frac12 \mu_0nI## at the sides of the solenoid too. (ie at/within the wires that make up the solenoid)...

In Theoretical Minimum: Quantum mechanics, Leonard Susskind describes an electron in the higher energy spin state in a magnetic field radiates a photon of energy ##\hbarγ|B_0|## and flips into the lower energy spin state. I am wondering if this photon is related to the "virutal photon" that...

Our class modified an experiment to measure the magnetic field strength in mT between 5cm and 30cm, and I have plotted data and found that the relationship resembles a power relationship (using a log vs log graph). In order to find the percentage uncertainty for the whole experiment I need the...

I find a exercise in Leonard Susskind's book Classical Mechanics the Hamiltonian of a charged particle in a magnetic field(ignore the electric field) is $$H=\sum_{i} \left\{ \frac{1}{2m} \left[ p_{i}-\frac{e}{c}A_{i}(x) \right]\left[ p_{i}-\frac{e}{c}A_{i}(x) \right]...

I have been analyzing a set of data from a lab activity on the Zeeman effect. The data (i.e. images) gathered can be previewed via this Google drive link here. While I am provided with the numerical data on the current (##I##), I am not provided with any data on the magnetic field. With the...

Summary:: Is the magnetic flux density B constant? Is the magnetic flux constant? I am working on a project design for Uni and I am stuck. In a magnetic circuit is either the magnetic flux or the magnetic flux density B constant? This magnetic circuit has all different cross section areas and...

When a magnet moves near a non-magnetic conductor such as copper and aluminium, it experiences a dissipative force called magnetic braking force. I am rather confused by the following explanation of magnetic braking force: The non-magnetic conductor here is the aluminium 'wall' seen on the...

https://www.physicsforums.com/attachments/282201 Are we using this equation above to explain this question? The magnetic field is definitely in sinusoidal form but how does it proportional to the frequency of the source?

Torque appiled by smaller disc = mga emf of disc due to B = Bwr2/2 Current I = Bwr2/2R force = IBr = Bwr3/2r torque = rF = Bwr4/2r mga = Bwr4/2r

I am confused about why spin down has a lower energy than spin up. What is the correct interpretation of the equations? If we have a spin ##\frac{1}{2}## particle in a magnetic field ##B_0## that is applied in the positive z direction The spin states of the particle are $$\ket{up} =...

I have a toroid with square cross section and 2 different circuit: ##C_1## where ##N=N_1## and ##I=I_1## ##C_2## where ##N=N_2## and ##I=I_2## I have a question that say I have to find the magnetic field ##B## produce by ##C_1## everywhere inside the coil. I assume here I have to find the...

Hi, I have to find the magnetic energy inside a coaxial cable of inner radius ##a## and outer radium ##b##, ##I = I## By using Ampere's law if ##r<a## ##B = \frac{\mu_0Ir}{2\pi a^2}## if ##a<r<b## ##B = \frac{\mu_0I}{2\pi r}## if ##r>b## ##B = 0## Then, the energy in a magnetic field ##E_b...

When I look at images of the pattern of iron filings around a magnet I cannot see any difference between the Pattern at the 'North' and 'South' poles. The present model also says that the field 'flows' from North to South but if this were the case it would not be necessary to move a magnet near...

Background Information (Not Strictly Necessary): As a quick recap, the graph I am dealing with is a semi-logarithmic graph of free induction decay (FID) amplitude as a function of time. To acquire the value for ##{T_2}^*## (and its uncertainty) in the graph, I used the below equation to do so...

Basic descriptions of spin such as the beginning of Lindley's "Where does the weirdness go" state that an electron's spin doesn't exist or is "indeterminant" until measured (e.g. passed through a Stern-Gerlach field). However, isn't the magnetic field nonzero essentially everywhere (albeit...

I was trying to show that the field transformation equations do hold when considering electric and magnetic fields as 4-vectors. To start off, I obtained the temporal and spatial components of ##E^{\alpha}## and ##B^{\alpha}##. The expressions are obtained from the following equations...

Hi, I have to find the motion of a particles ##(x,y,z)##. However, I'm not sure where to begin. Is it correct to split the problem and first find what's the motion in the x direction then y and z. For exemple, ##m \frac{d^2x}{dt^2} = -kv_{0x} + qv_{0x}B sin 90 ## ##m\int\int...

1. When two parallel wires carry current in the same direction, they exert equal and opposite attractive forces on each other. 2. ε=lvBsinθ ε=0.02*5*0.1*sin30 ε=0.005 V 3. Well, a conductor moving through a magnetic field has the potential to induce an emf, but this movement must be in such a...

Are you saying there are circumstances in which the work done in a magnetic field depends on the path taken?

I attempted to run a lab that would allows us to calculate the magnetic field strength of a couple different neodymium magnets. I would love some feedback on it and ways that I could potentially make it better. The numbers I calculated were very far off from what I expected. Apparatus set up: I...

The force on a charged particle that is moving through a magnetic field is explained in introductory physics textbooks. The magnetic field cannot change the kinetic energy of the charged particle because the force from the magnetic field is always perpendicular to the velocity, so no work is...

On the first attached page ##\mu_z## is associated with orbital angular momentum (Eq. 41.34). On the following pages (Eq. 41.38) it is associated with spin angular momentum? Are these both part of the same thing? I tried to read further but the book does not address this. In example 41.6 it...

Ok so here is something that made me scratch my head and I still can't come to a final conclusion. The basic idea is seemingly simple. You have permanent magnets attached to a core, the field lines close on both magnets through the core, so far so good. but the core also has electromagnets , put...

I calculated in this way as attached and got the correct answer. However I still wonder why the magnetic flux is the same in both coils, or this presumption is not right.

here is the question, don't mind about point (a) and (b) because i have solved them already...the main problem is the question on point (c) : so far, what i have done is : H = 2.7*0.1-(1.4*0.15+1.3*0.25) = -0.265 az A/m which is the wrong answer compared to the solution provided from the...