What is Magnetic field: Definition and 1000 Discussions
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a magnetic field that varies with location will exert a force on a range of non-magnetic materials by affecting the motion of their outer atomic electrons. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, they are described as a map assigning a vector to each point of space or, more precisely—because of the way the magnetic field transforms under mirror reflection—as a field of pseudovectors.
In electromagnetics, the term "magnetic field" is used for two distinct but closely related vector fields denoted by the symbols B and H. In the International System of Units, H, magnetic field strength, is measured in the SI base units of ampere per meter (A/m). B, magnetic flux density, is measured in tesla (in SI base units: kilogram per second2 per ampere), which is equivalent to newton per meter per ampere. H and B differ in how they account for magnetization. In a vacuum, the two fields are related through the vacuum permeability,
B
/
μ
0
=
H
{\displaystyle \mathbf {B} /\mu _{0}=\mathbf {H} }
; but in a magnetized material, the terms differ by the material's magnetization at each point.
Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. Magnetic fields and electric fields are interrelated and are both components of the electromagnetic force, one of the four fundamental forces of nature.
Magnetic fields are used throughout modern technology, particularly in electrical engineering and electromechanics. Rotating magnetic fields are used in both electric motors and generators. The interaction of magnetic fields in electric devices such as transformers is conceptualized and investigated as magnetic circuits. Magnetic forces give information about the charge carriers in a material through the Hall effect. The Earth produces its own magnetic field, which shields the Earth's ozone layer from the solar wind and is important in navigation using a compass.
I want to wrap no. 16 copper wire around 1" copper pipe to create a mag field. At 120v / 1 amp AC, how many turns will I need to get about 5 milligauss near the pipe?
I've just started Quantum mechanics
by McIntyre and have understood the following about operators which the author wrote till chapter 2:
Each observable has an operator
Operators act on kets to produce another kets.
Only eigenvalues of an operator are possible values of a measurement.
Now...
Consider an uncharged particle with spin one-half moving with speed ##v## in a region with magnetic field ##\textbf{B}=B\textbf{e}_z##. In a certain length ##L## of the particle's path, there is an additional, weak magnetic field ##\textbf{B}_\perp=B_\perp \textbf{e}_x##. Assuming the electron...
Since the question says that "velocity along the cylinder axis" and "magnetic field perpendicular to the cylinder axis". So cross product of velocity and magnetic field becomes their magnitude.
##\vec v\times \vec B=||v|| \\ ||B||##
So
##\vec F=qvB##
##mg=qv\frac{\mu_0 nI}{4\pi r}##
At first...
From ##\oint_{\Gamma}\vec{H}\cdot d\vec{l}=\sum I## by Ampere's Law which gives ##H \Delta l=\Delta N\cdot i\Leftrightarrow H=n i## where ##n=## number of turns per unit length so ##i=\frac{H}{n}=\frac{10^3 A / m}{\frac{200}{0.2m}}=1 A##.
Since ##\vec{H}=\frac{\vec{B}-\mu_0\vec{M}}{\mu_0}## we...
When I try following numbers from internet then I don't get an expected answer.
## \mu_0 = 1.25663706 × 10-6 m kg s^{-2} A^{-2}##
##q =1.60217662 × 10^{-19} coulombs ##
##r=2.82x10^{-15} m##
Velocity of that electron is given in question
##\vec v= 2 \times 10^6 \\ \mathrm{ms^{-1}}##Since...
If I want to carry 10 A through an 8 AWG wire, I understand that there will be a specific magnetic field around the wire which will decrease as I move outward from the wire radially. Let's consider the center of that wire as coordinates (x,y)=(0,0). An object located at (0,10) would see a...
Hello everybody!
I have a question concerning the Fourier transformation: So far I have experimentially measured the magnetic field of a quadrupole but as the hall effect sensor had a fixed orientation I did two series, one for the x, one for y component of the magnetic field, I have 50 values...
Hello all,
what would happen to a perfectly conducting cylinder immersed in a rotating magnetic field, with the rotation axis parallel to that of the cylinder? I guess the cylinder would start to rotate with the field? Right?
Thank you
Hey, I was trying to figure out this problem. I got (a) using B = mu * NI/L
but I'm not sure how to start the part about the magnetic field in the gap after the solenoid is ripped in half with 1 cm gap.
Thanks for the help!
Hi all, my work is shown on the attached image. The boxed equation is what I get to but I do not understand how to go from there to what the book has. I am guessing that the problem arises when trying to solve the cross product. I understand that I will need to find the value of the sine of the...
So when evaluation the cross product of the velocity of the charge and the unit vectors associated with the point I am getting
v x r = j x [ i + j].
Well j x j is 0.
j x i = -k, but yet the answer is positive. Why is this?
Hi Pfs.
I think that QM can explain the classical things explained by classical physics. Using mean values and so on.
We know that in a constant magnetic field an electron will rotate on a circle (at the macroscopic scale approximation)
I have the answer for the Larmor precession but how to...
I used the above equation, and started with getting the cross product of dl and r, which was equal to 0.00195i+0.00365k. From there, I divided each component by the magnitude of radius cubed (0.827^3). I then multiplied by I and u naught(u_0=4pi*10^-7), and then divided by 4pi. The answer I got...
Hello,
I have used an edge current of 10 A through a 0,45 cm (lenght) wire inside an air sphere. The thing is that, according with Ampere law, the magnetic field (B) produced at a 1 mm of distance from the wire shall be 0,002 T, and I am obtaining much higher values in this simulation (around...
Hello!
I tried to solve a) see figure below, is it correct?
b) so what I think I can do is to solve ## M_{12} ## from the equation of the magnetic flux then I will get ## \frac{\Phi}{I} = M_{12}## Then I can even use the equation får the magnetic flux and the magnetic field $$ \Phi = \int \vec...
I don't have access to high power systems, or ultra precise detectors.(around 10V/ 1A)
Can I detect small variations (frequencies ?) of magnetic field, while ignoring the noise caused by the Earth's magnetic field ?
My goal is to measure the magnetic field through a line in order to trace it...
The first part of the problem seems easy enough, the free electrons in the wire would move in a circle owing to an electric field that would be induced in the rod which would provide the centripetal force for the same (Please correct me if I am wrong). So we have $$eE=mω^2x$$, where e is the...
Hi all, first time on this forum.
I know this may sound like a stupid question, but how does the magnetic field distribute?
I am working on FEMM and i am analysing magnetic losses on steel ducts. I was checking the flux density and the magnetic field distributions and i was surprised when i...
I have been trying to calculate the magnetic flux thought a single loop of wire occurring from a magnet (meaning it has a nonuniform field), so I have the following equation:
Φ=∮BdAcosθ
Now my problem is that I do not know how to calculate the magnetic field strength (B)of that magnet (which...
Hello,
I would like to know what is the magnetic field of a half toroid.
Would we use Ampere's law? So, considering that the integral is equal to BA, we would have BA = μo * i, then B = (μo * i) / r. But, using Biot-Savart's law, by symmetry, it seems that the vector sum of all the...
When I read things about magnetism on internet, I don't understand at all about one thing:
If a moving particle receive a force if it's in a magnetic field, so it should accelerate, so what happen if we change the referential so that the particle now don't move?
The particle shouldn't receive...
And if a star is severely stretched by tidal force, how does that affect its magnetic field and the process of it collapsing at the start of a supernova?
I could solve a similar (rather, a specific case of the above) where the current entered through a
corner and left from the corner opposite to it along the body diagonal of the cube. For this specific case, I was able to easily exploit symmetry to deduce the answer (0). However, I cannot think...
In NMR, protons that are near each other exchange energy with each other by photon emission and absorption.
Proton A is spin down, and proton B is spin up. proton A emits a photon and becomes spin up, and proton B absorbs this photon and becomes spin down. have the two protons been entangled?
Hello, I asked a question about superconductors in 2020 and I was now wondering what superconducting chemical/material can have the highest magnetic field strength before the superconductivity is destroyed by it? Secondly, What the is maximum magnetic field strength of said material in Tesla per...
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...
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...
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 all,
I've recently become transfixed with the idea of magnetism and gravity.
I have two main questions I'd like to see discussed more.
1. Would it be possible to harness magnetic fields for energy on earth/for acceleration between planets?
1a. Has this been studied at all?
2. Why do we...
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...
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...
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...
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...