Magnetic field Definition and 1000 Threads

I don't understand why a force would be acting on this rectangular coil at all. The magnetic field of the wire would only induce a force on the coil, if the coil had a current flowing through it. At first I would think that the electric field from the varying magnetic field would induce such...

For if the axis of symmetry is oriented along the y-axis I have gotten as far as converting the main integral entirely to cartesian coordinates. $$\hat{\phi}=-sin(\phi)\hat{x}+cos(\phi)\hat{y} \therefore \hat{\phi} =-sin(tan^{-1}(x/y))\hat{x}+cos(tan^{-1}(x/y))\hat{y}$$...

The question is to find the magnetic field immediately outside a thin hollow cylinder that carries a uniform steady current I on its surface. This is my solution but what I get contradicts amperes law.

So I was able to do out the curl in the i and j direction and got 3xz/r5 and 3yz/r5 as expected. However, when I do out the last curl, I do not get 3z2-3r2. I get the following \frac{\partial}{\partial x} \frac{x}{(x^2+y^2+z^2)^\frac{3}{2}} = \frac{-2x^2+y^2+z^2}{(x^2+y^2+z^2)^\frac{5}{2}}...

Where should I start?

Hello, there are a couple things about magnetism that I do not understand. 1. Why didn't we define the magnetic field to be in the directions of the force? This isn't really a technical question, I am just more curious about why it is this way. The way I was thinking of it, the math seems to...

Hi. In a current carrying conductor because of special relativity amount of protons and electrons differ so we get an electric field or as we call it magnetic field. So if magnetic field is just an electric field how is it that the charge has to move so that magnetic field would exert a force on...

With talk of the Earth's magnetic field slowly moving, (enough to cause navigational issues I've heard) does it effect how the sun's ray hit us? For example, the Northern Lights are solar partials interacts with the magnetic field (I think). If the poles moves, would it affect the effectiveness...

Hello all, I have a question with the helix path of proton in a magnetic field that I am a bit stuck on. Question: Equations: F = qv X B F = mv^2/r d=vt My Attempt: Think the graph drawn is good enough for questions (a). However, I am stuck on (b) and (c). Firstly I am not entirely sure...

So my thought process is as follows, since the initial centripetal force and the second magnetic force are working together, we can set up an equation to calculating final frequency. However, I am struggling with how this can be done given so little numbers. mvi^2/r + qvB = mv^2/r Am I on the...

Hi all, I have a question which I think should be a simple solve for most people but I cannot seem to get my head around it. It is a common case in geophysical surveying that a magnetic field vertical gradiometer might be used. This instrument uses two magnetometers separated by a known...

Suppose I had an electromagnet that would instantly go to full power when turned on (impossible) and at one light second away a detector capable of detecting the electromagnet. When I turn the electromagnet on how long does it take for the field to reach the detector?

Does the Earth have a charge? so magnetic field? Is there a function to its distribution on the Earth surface? If there's a free charge on the air will it effect by it?

Hello Friends, I have been wondering, is it possible to construct a motor, and attach a coil to it, such that with the motion due to the rotation of the motor, it generates a excess of energy that can be used to power the motor in turn, basically, could i use the excess to charge a battery that...

Homework Statement An electron is at rest in an oscillating magnetic field $$ \mathbf B = B_0 cos\left( ωt \right) \hat k $$ where ##B_0## and ##ω## are constants. What is the minimum field (##B_0##) required to force a complete flip in ##S_x##? Homework Equations $$H=- γ \mathbf B \cdot...

Hi there, we are developing a small consumer electronics product consisting of a small 4-layer PCB along with a few PDM microphones and BLE chip/ and antenna, as well as a LiPo battery. We are locating a small but pretty strong magnet next to these components in the enclosure. It is an N52...

Homework Statement I want to find the solution to the following problem: $$\begin{cases} \nabla^2 B=c^2 B &\text{ on the half plane } x>0 \\ B=B_0 \hat{z} & \text{ for } x<0 \end{cases}$$ in the ##xz## plane. ##c, B_0 \in \mathbb{R}## Homework Equations I am not really sure what would be...

Hi! I'm new here. I took physics back when we calculated pterodactyl drag and I remember what an integral looks like but that's about it. I hope I chose the right prefix. What I'd like to do is find the dimensions of N48 neodymium cylinder magnets that would produce a minimum field strength...

Homework Statement Imagine an infinite straight wire pointing at you (thus, the magnetic field curls counterclockwise from your perspective). Such a magnetic field equals to: $$B = \frac{\mu I}{2 \pi s} \hat{\phi}$$ I want to calculate the line integral of ##B## around the circular path of...

Homework Statement A proton moves through a uniform magnetic field given by B=(13.7i−22.9j+23.5k) mT. at time t1 v=(vxi +vyj+1.68k)km/s and the magnetic force is given by F= (4.22e-17i + 2.52e-17j). What are vx and vy Homework Equations F=q(v x B) The Attempt at a Solution First I converted...

Hello I am bemused by a sign convention for Holes, My questions are as follow: For an electron inside the 2D Circular Quantum Well. We can write our Hamiltonian as H = 1/2m * ( p - q A)^2 + 1/2 m w^2 r^2 (Should we use minus in the momentum term? I think for Holes, it is) If we expand this...

I know the magnetic flux inside a hollow conductor is zero. Is this also true if the observer is inside the conductor and the conductor is rotating in relation to the observer so that the electrons are traveling in spirals around the hollow center?

Quick question from an amateur: Assume you have a tidally locked rocky planet around a red dwarf star. I've heard that a magnetic field is or can be dependent upon the rotation of a planet (I've read that the lack of rotation of Venus was a possible reason for the weak magnetic field among...

Homework Statement A superconducting spherical shell of radius R is placed in a uniform magnetic field ##\vec{B_0}## 1)Find the magnetic field everywhere outside the shell 2)the sutface current density Homework Equations Inside the shell the net magnetic field is 0, and at the surface also...

Hi! I had this problem for homework (Mastering Physics), and I'm not sure what I'm doing incorrectly. Is there something fundamental that I'm misunderstanding? Each time I do this, I get 0.717136.. T as my solution 1. Homework Statement I = 12.6 A w = 0.0142 m t = 0.00122 m E_H = 1.82 *...

I am currently working in astromagnetism. My question is, somebody knows if a fermi gas (degenerate electrons) can increase or decrease de total magnetic field due to an influence of an external magnetic field and if somebody have information about that. I know that an external magnetic field...

We all know a moving charge generates a magnetic field. A moving charge also generates a displacement current ∂E/∂t. Is the magnetic field generated entirely due to the presence of the displacement current, or is there an independent, separate effect which contributes to the magnetic field?

Homework Statement There is a square loop with mass of 4.0 kg and side length 4.5 m that is tilted upwards from the ground at a 25 degree angle with one side resting on the surface. The loop is a conductor that has 25 A of current going through it. The question asks to find the strength a...

Homework Statement Suppose we have an isolated, long, narrow straight wire with low electrical resistivity. A constant current ##I## is sent through this wire. We know that if an electron is sent on a path which is perpendicular to the wire, towards it, with an initial speed ##v_0##, and the...

A uniform beam of positively charged particles is moving with a constant velocity parallel to another beam of negatively charged particles moving with the same velocity but in opposite direction separated by a distance d. Then, how should be the variation of magnetic field B along a...

The Earth’s magnetic field is slowly moving with respect to the Earth’s surface and to the Sun’s incoming radiation and solar wind direction. Does the tilting/moving of Earth’s magnetic field axis to the incoming solar wind direction change the protection on different points of the Earth’s...

Hi. This picture shows an iron ring shielding a static magnetic field: Does this really work, and why? I know that a conductor can shield an electric field (Faraday cage) and a changing magnetic field (Lenz's law), but why would it shield a static field? Especially since iron is a ferromagnet.

How can we calculate the magnetic field of moving charge by the Maxwell equation ##\nabla \times H=J+\frac {\partial D} {\partial t}##? I mean which term, ##J## or ##\frac {\partial D} {\partial t}##, should be taken into account in calculations? The first, second, or both? Can we deal with the...

This is about the history of electromagnetism. I already know about the convention that defined which electric charge is the "positive" one, which ended up making the electron a negative particle. But what about the "positive" direction of the magnetic field? Does anybody here know how it was...

1. The question... "Blood is a conducting fluid. When flowing through an artery of diameter 10mm which is subject to a constant magnetic field of strength 60mT, an e.m.f. of 0.3mV appears across the width of the artery. Calculate the speed of the blood" 3. The solution... The solution given...

I have a question why a magnet's magnetic field or a coil's magnetic field will not oppose the Earth's magnetic field? Is it because the Earth's field is not strong enough or the magnet/coil doesn't cover enough square area? What formula's would I use to figure out what strength or area I...

So, I have had a bit of a look around and can't come up with a concrete answer, so I thought I'd post my curiosity on here! What is the direction that a compass points in 3 dimensional space, and how is this affected by proximity to North? to clarify what I mean: We all know that compasses...

In the attached picture, the outer wire is carrying a current I(t), and it's asked to find the induced EMF in the inner loop. Now I have indeed calculated the B-field along the z-axis due to the outer loop. My lecturer then puts z=0 into that expression and then multiplied it with the area of...

As shown in the figure, in the Meisner effect, the magnetic field of the magnet bypasses the superconductor. My question is, does the magnetic B field belonging to the magnet increase at the arrow indicating position? Or is there no change in the intensity of the magnetic field that belongs to...

As shown in the figure, the aircraft includes a geomagnetic field convergence layer, which is a superconductor material. The geomagnetic field convergence layer repels the direction of changing the geomagnetic field, so that the geomagnetic field passes between the upper and lower converging...

Homework Statement There's a very long cylinder with radius ##R## and magnetic permeability ##\mu##. The cylinder is placed in uniform magnetic field ##B_{0}## pointed perpendicularly to the axis of cylinder. Find magnetic field for ##r < R##. Assume there's a vacuum outside the cylinder...

Homework Statement A 40 cm rod is rotated about its centre inside a region of uniform magnetic field of 6.4 T. Given that the speed of rotation is 15 rad/s, find potential difference between the centre and either end of the rod Homework Equations emf = - ΔΦ / Δt ω = 2π / T The Attempt at a...

I have a basic question about magnetic fields, but the answer will help me better understand quantum collapse issues. If the current in a wire is instantaneously shut off, what happens to the magnetic field that was present when the current was flowing? To be more specific: Wire...

Homework Statement A particle of mass M, with charge Q is left at the point A. After reaching point P the particle is at the effect of a constant and uniform magnetic field of intensity B reaching point Q. Find H. Homework Equations P=mg Fm=qvB Ke=(mv^2)/2 U=mgH The Attempt at a Solution...

Particles follows accordingly the general equation: $$ m*\overrightarrow{a}=q*\overrightarrow{E}+q*\overrightarrow{v}\wedge \overrightarrow{B} $$ But in the case of two coupled coils the time varying current at primary coil (and its magnetic field variation) creates corresponding varying...

The problem: a coil of radius r, length l and N turns, rotating with constant angular velocity ω around an axis perpendicular to its simmetric axis and passing for the center of the coil. The coils is submersed in a static magnetic field, intensity B0, perpendicular to the axis of rotation of...

I am trying to derive the equation ##\vec{\Gamma} = \vec{m} \times \vec{B}##, where ##\vec{m} = I \vec{A}## is the magnetic moment, and ##\vec{A}## is normal to surface ##A##, from the Lorentz force law ##\mathrm{d}\vec{F} = I \vec{dl} \times \vec{B}##. For an arbitrary closed current loop ##C##...

Homework Statement A square coil (sorry, its not "current carrying" as shown in diagram, my mistake) of length L is released from rest, in a horizontal uniform magnetic field going into the plane of paper, of length 2L. What can you say about the coil's acceleration? Homework EquationsThe...

Homework Statement From near to the center of the solar disc, Fe I line emission from point X shows a spectral line with components 666.823, 666.830 and 666.837 nm, around the rest wavelength of 666.800 nm. The central component is not as bright as those at the longer and shorter wavelengths...

I'm not sufficiently educated on this stuff to properly describe the question. Sorry. Consider the following. a primitive gauge is set up in order to observe the differential air flow between two sources. Assuming static pressure linearly corresponds to differences in flow. so balancing air...