Magnetic field Definition and 1000 Threads

Hi, I've been wondering what causes a magnetic field, current or an electric field. If you had a material with extremely low susceptibility and extremely high permeability then what would cause a magnetic field in this material, a current or an electric field (as long as whatever is causing the...

Can we predict the movement of a magnet in a uniform magnetic field using Maxwell's equations? What if the magnetic field is variable, for example if we have two magnets moving in a reference frame? Thank you for any answers and I wish you a Merry Christmas! :)

We all think that electric current is the electrons flow without mass transfer in conductor, i.e. charged lepton flow. But charged baryons flow can also deemed as "electric" current, e.g. ionic current. My question is that charged baryons flow can induce magnetic field? Same amperes, then same B...

What if you had a charge with a negligible radius and infinitely strong magnetic field or electric charge? Would it form a black hole of infinite mass?

Homework Statement a circular coil of radius 120 mm with 10 turns is placed with its plane parallel to the Earth magnetic field . when a current of 0.45 A flows through the coil , a compass needle placed at the centre of the coil is seen to be deflected by an angle of 45 degree to the plane of...

Homework Statement Find (a) the module and (b) the direction, entering or exiting the page plane, of the magnetic field at point P, knowing that a = 4.7 cm and i = 13 A Homework Equations Biot-Savart law The Attempt at a Solution For 1-2 and 4-5 segments, B = 0 because sin θ = 0 for...

Homework Statement I am having a issue with calulating my errors for this particular experiment the reason I will detail below. I have also print sceend in the section of my lab report to show the experimental setup etc. Lab Script So in the lab during the experiment the tesla meter...

Hi!, I have a question for you geniuses (geniusi?) Why are there two different equations to find the magnetic field of a solenoid and a coil with multiple turns? (According to my textbook) The equations for each are Solenoid: Coil with multiple turns: Why are they different? Is there a...

Homework Statement Homework EquationsThe Attempt at a Solution Using ## \nabla \times \vec A = \vec B##. I got that both ##\v A_1 ~~and~~ \vec A_2 ## produce ## \vec B##. So, the correct option is (d). Is this correct? [/B]

Homework Statement The circuit shown is in a uniform magnetic field that is into the page. The total current in the circuit is 0.20 A, flowing counterclockwise. At what rate is the magnitude of the magnetic field changing? Is it increasing or decreasing? Square wire loop with base and height...

Homework Statement Here is a link to the problem: https://imgur.com/a/0T9sF I am having trouble finding the time it takes the loop to leave the field in part a. Homework Equations ## emf=-\frac{d \Phi}{dt} ## ## \Sigma F=ma=mg-BIl ## ## \frac{dv}{dt}-\gamma v=g ## where ##...

Homework Statement A rotating magnetic dipole is built by two oscillating magnetic dipole moments, one along the y-axis and one along the x-axis. Find the vector potential at a point: (0, 0, ##z_0##) along the z-axis. Then find the magnetic field at ##z_0## . As the magnetic field is a function...

Hi everyone, Lately I have been studying the Poynting Flux and I am familiar with the classic examples of how it can be used to describe the power being dissipated by a resistor and the energy flowing into a capacitor, but I have never come across a similar analog for how the Poynting flux...

Homework Statement A force of 2.4N is exerted on a -1.8µC charge in a downward direction. What is the magnitude and direction of the magnetic field at this point? (The assignment sheet is called "Electrostatics Questions", hence the "Electrostatics?" in the title) Homework Equations Electric...

I have a question connected with the problem: https://www.physicsforums.com/threads/continuity-equation-in-an-electromagnetic-field.673312/ Why don’t we assume H=H*? Isn’t hamiltonian in magnetic field a self-adjoint operator? Why? Why do we use (+iħ∇-e/c A)2 instead of (-iħ∇-e/c A)2 two times?

Homework Statement Two particles having mass m separated by a distance d is uniform magnetic field as shown in the figure . If v=qBd/m, at what instant does collision occur. The coulomb force between the particles is switched off. Homework Equations T=2πm/qB The Attempt at a Solution For the...

Homework Statement A current I flows along the surface of a hollow conducting cylinder. The radius of the cylinder section is r. By using Ampere's law, show that the magnetic field B outside the cylinder is B=\frac{\mu_0}{2 \pi} \frac{I}{r} Homework Equations Ampere's law...

Homework Statement A thick slab in the region 0 \leq z \leq a , and infinite in xy plane carries a current density \vec{J} = Jz\hat{x} . Find the magnetic field as a function of z, both inside and outside the slab. Homework Equations Ampere's Law: \oint \vec{B} \cdot d\vec{l} = \mu_0...

If an AA battery were placed in some kind of ideal conducting 'ether': 1) Would current flow, and if so, what would the flow of electrons look like? 2) How would the magnetic field look? (I imagine that if there was an electric current flowing, that the magnetic field would look a little like...

Homework Statement If you were to gain a few electrons and go running in Vancouver, what would be the magnitude and direction of the magnetic force that you would experience? Homework EquationsThe Attempt at a Solution So I was able to determine the magnetic force but my only problem is...

[Mod Note: Thread moved from Classical Physics, hence no formatting template] So today we performed an experiment to measure the Earth's magnetic field in three dimensions. For one of the dimensions we got 6.6x10^-5 i We were wondering if an imaginary magnetic field was possible and what it...

Homework Statement The xy-plane serves as the interface between two different media. Medium 1 (z < 0) is filled with a material whose µr=6, and medium 2 (z > 0) is filled with a material whose µr=4. If the interface carries a current (1/µ0)ˆy (y- hat) mA/m, and B2 = 5ˆx (x-hat) + 8ˆz (z-hat)...

I was just in a conversation with someone regarding the magnetic field resulting outside of a solid cylinder, with a current moving down the center of the cylinder, and then the resulting magnetic field after removing the current. Now I haven't thought about magnetic fields/magnets for a while...

Hello. I am reading a paper which says that only Earth (between the rocky planets) keep a strong magnetic field and it arose an question on this: Why does the magnetic field of the planets decrease with time in such planets? Why the magnetic field of the Earth is the only one which keeps strong?

I would like to fine the kinetic energy of a cone that rotates around its symmetry axis. I consider that the cone is formes by infinite cylinders with different radius and infinitesimal height. I end up with this result: K=1/4w^2R^2hM where w is the angular velocity R the radius h the height and...

Hi, everyone. I'm working on a project right now where I need to amplify an AC signal to create as much current as possible in a solenoid to generate as strong a magnetic field as I can. I'm likely dealing with a maximum of 10 V and 10 mA from my signal generator, but I ideally need a peak...

Homework Statement It is shown in more advanced courses that charged particles in circular orbits radiate electromagnetic waves, called cyclotron radiation. As a result, a particle undergoing cyclotron motion with speed v is actually losing kinetic energy at the rate $$\frac{dK}{dt} = -...

Homework Statement An infinitely long cylinder of radius R carries a "frozen-in" magnetization, parallel to the axis, ## \vec M = ks \hat z ##. There are no free currents. Find the magnetic field inside and outside the cylinder by two different methods: (a) Locate all the bound currents and...

Hi Forum I am trying to get a better grasp of the relation between electric field and the magnetic field. The overall question is "What is The origin of selfinductance in a current loop?" Here are my thourghts: A battery is connected to a say circular wire with some resistance. The current...

If you have uniform magnetic field, would something like a halbach array which has a non symmetrical magnetic field experience a net force? If not, is there any way to shield one side of a magnet so that it would experience a net force? On a similar note, if you wound a wire around a sphere in...

Homework Statement A metal rod of mass M and length L is pivoted about a hinge at point O as shown in Figure P32.80 (I have attached this to this post) The axis of rotation passes through O into the page. Find the ratio of the maximum electric field inside the rod to the applied magnetic field...

Homework Statement [/B] A short current element dl⃗ = (0.500 mm)j^ carries a current of 5.20 A in the same direction as dl⃗ . Point P is located at r⃗ = ( -0.730 m)i^+ (0.390m)k^. Find the magnetic field at P produced by this current. So basically what they are asking me for is the x, y, and...

Homework Statement The Hamiltonian of a spin 1/2 particle is given by: $$H=g\overrightarrow { S }\cdot \overrightarrow { B } $$ where ##\overrightarrow { S }=\hbar \overrightarrow{\sigma }/2## is the spin operator and ##\overrightarrow { B }## is an external magnetic field. 1. Determine...

Homework Statement Homework EquationsThe Attempt at a Solution Velocity of particle at any time t is v = vxi + vyj Net Force on the particle F = (2qvyB)i + (2qvxB)j Net acceleration of the particle = F/m Magnitude of net acceleration = (2qvB)/m Particle has an initial velocity as well...

My physics teacher said that the northern lights are the product of charged particles coming from the sun and interactign with our atmosphere. I believe he said that these are deflected by Earth's magnetic field and directed towards the North and South poles. When I look at pictures on this...

Homework Statement Homework EquationsThe Attempt at a Solution As soon as switch S is closed , a current would flow in the circuit and the capacitor would act like a conducting wire . Force F =ilB towards right will act on the slider . There will be an acceleration but the velocity of the...

Any pure state of spin-1/2 particle can be represented by a superposition of spin up and spin-down relative to an arbitrarily direction. lw>=a l+> + b l-> where a^2+b^2=1 If there is no magnetic field, the measurement of the spin is random and we get 50-50 chance to be spin up and spin down...

Homework Statement Find the exact magnetic field a distance z above the center of a square loop of side w, carrying a current I. Verify that it reduces to the field of a dipole, with the appropriate dipole moment, when z >> w. Homework Equations (1) dB = μ0I/4πr2 dl × rhat (2) r =...

Homework Statement One person that we will call him - A is standing on an infinite charged non conductive panel with velocity V=(-Vx0,0). A is throwing a particle q with V=(Vx0,Vy0). The other person - B, is start running below the particle at t=t0. A thinks that B will see the particle above...

Homework Statement I have a solenoid with a wire carrying current in the center. The wire has a radius of a, the solenoid has a radius of b. I need to find the magnetic field inside of each region. Inside of the wire, mu =/= muo. Homework Equations Wire B field = uo I/2*pi*r Solenoid B field...

Hello, I have a doubt about the Complete Set of commuting observables (CSCO) in the cases when there are a magnetic field ##B## in z. The statement is find the constant of motion and CSCO for a particle of mass m and spin 1/2, not necessary a electron or any atomic particle. I know that the...

Homework Statement Homework EquationsThe Attempt at a Solution In this problem as the rod moves towards right, magnetic force of magnitude ilB starts acting towards left on the rod.This decreases the speed of the rod .The EMF induced in the rod is Blv where v is the instantaneous speed of...

Homework Statement https://imgur.com/gallery/vCOZq Its question 26, and the figure can be seen at figure 30.26 Derive and expression for the magnetic field produced at point P due to the current carrying wire shown in figure 30.26. The curved parts of the wire are pieces of concentric...

Homework Statement (a) What voltage will accelerate electrons to a speed of ##6.00 \times 10^{-7} m/s## ? (b) Find the radius of curvature of the path of a proton accelerated through this potential in a 0.500-T field and compare this with the radius of curvature of an electron accelerated...

PICTURE INCLUDED 1. Homework Statement A piece of wire is bent into an isosceles right triangle whose shorter sides have length a The wire carries current I. Calculate the magnetic field for point P. Point P is located on the Y-axis ( 0, √2a). Two corners of the triangle are are located at...

If I keep iron fillings on a cardboard with a wire carrying current in some direction, I know that the fillings will orient in concentric circles.But what happens if I keep the fillings on the underside of the cardboard? Is it possible to make them hang in the air against gravity with a...

As a SP phenomena I thought this may be the best sub to post this. We understand how current creates a magnetic field, and almost all forms of current are really electron flow. My question is - are there any known (real world) examples of positive particle flow, creating a magnetic field...

Homework Statement The Lorentz Force can be used to sort ions (atomic or molecular) based on their charge to mass ratio. This configuration has been used to separate isotopes and as a mass spectrometer. A beam of Strontium ions Sr+ is accelerated through a potential of 500 V and injected into...

Homework Statement In a homogeneous, non-magnetic, highly insulating and viscous medium, a moving particle experiences a viscous drag given by the law f→=−bv→. Here b is a positive constant. A particle having charge q is projected with an unknown velocity from a point in the medium. It almost...

Homework Statement suppose we have a charging capacitor orientated along the z-axis, such that we have a changing electric field. How do I determine the direction of the associated magnetic field. Homework EquationsThe Attempt at a Solution I calculated the magnitude of the B field, and my...