Magnetic field Definition and 1000 Threads

Apart from the orientation of a compass needle and the pattern formed by iron filings, what other proof do we have of magnetic field lines forming loops?

Hi, I'm developing a new bio reactor, which in this instance you can think of as just a perspex fish tank. But have come across an unusual requirement to apply a roughly 0.01T magnetic field across the volume of the tank with mainly water in it. No position in the tank can be less than 0.08T and...

Hey guys, So I have a bit of an interesting problem to solve here. I'm trying to calculate the upward repulsion force due to eddy currents created in a conductive surface by a rotating magnetic field. I'm doing this for an undergraduate lab project, and want to be able to provide quantifiable...

Magnetic field do no work. Is this always true? If so then what is the explanation of that crane thing?

I was just wondering if a beam of whatever charged particles can be compressed in velocity space if you send the beam through a (strong) magnetic field that is parallel to the beam? The charged particles (that are not moving exactly along the field lines) should spiral in the field in my opinion...

Can someone please explain to me why, a changing magnetic field can produce an electric field and a changing electrical field can produce a magnetic field. Also how do magnetic fields originate, what causes them?

Hello everyone I have a question: I know what alpha/omega dinamo is, and I think I have understood how this model explains Joy's law and Hale's law, but I don't get how it allows the magnetic field to become poloidal again (after having become toroidal due to differential rotation) and with the...

Lorentz force equation shows us that current is proportional to the force. Is it safe to assume that the force generated by an AC current at 60Hz will always have the same frequency? In other words, as the current increases and deceases (sinusoidal) the force will follow the same pattern at the...

Hello all, I know that the force due to magnetic field on a wire containing current = the length of that wire* the current intensity x magnetic field upon that wire, but I fail to understand where the "the length of that wire* the current intensity" comes from or why it's even there. Sometimes...

Let's see delocalized electron cloud on a surface of a metal (a piece of iron for example): When a strong Nd magnet get close the spin of these electrons allign to the magnetic field but the electrons don't move. Why? The force is not canceled out. Electrons should move and compressed in one...

Homework Statement I found solution to problem 257 from "300 Creative Physics problems" hard to understand. In that problem we have very long solenoid with coil wounded in one layer. Data such as: density of turns, magnetic field at distance of 5 cm form the axis of solenoid and diameter (1 cm)...

Homework Statement A conduction rod (of mass ##m## and length ##l##) was placed on two smooth conducting rails rails connected by a resistor as shown: (the circuit is placed in ##XY##-plane A constant uniform magnetic field is switched on along ##-Z## direction with magnitude ##B## The rod is...

Homework Statement A cathode ray tube (CRT), consisting of an electron gun and a screen, is placed within a uniform constant magnetic field of magnitude B such that the magnetic field is parallel to the beam axis of the gun, as shown in figure...

Does time run slower or faster in a magnetic field?

When a large amount of plasma radiates greatly while accreting on a magnetized neutron star, where does the radiation ultimately get its energy from, the magnetic field and/or gravitational field? Without doing the numbers, if the magnetic field does the work against the gravitational field, and...

Homework Statement A coaxial cable consists of an inner cylindrical conductor of radius R1 = 0.040 m on the axis of an outer hollow cylindrical conductor of inner radius R2 = 0.080 m and outer radius R3 = 0.090 m. The inner conductor carries current I1 = 4.4 A in one direction, and the outer...

Homework Statement A coil, made up of 1850 loops, is inserted in an electric circuit and has a resistance of 45,0Ω. The area of each loop is 4,70⋅10^(-4) m^(2). The coil moves from a region where there's no magnetic field, to a region where the magnetic field is present. The normal to the coil...

Homework Statement Question I need help with: If wire AB of problem 9 moves with a velocity of 50.0 m/s to the right, at what rate should B change when the wire is at a distance of 5.00 cm from the left end of the loop, such that there will be no induced emf in the circuit? Answer: 300 T/s...

1. The field strength of the Earth is 5x10^-5 T at the surface. Space shuttles orbit the Earth at a speed of 7860 m/s . They orbit at an altitude of 322 km. If we assume that a single current loop at the Earth's radius is generating the magnetic field, then what is the current? Determine the...

Homework Statement Two long wires (in cross section) that each carry a current ##i## directly out of the page. What is the magnitude of the field at point ##P##, which lies on the perpendicular bisector to the wires? Homework Equations ##B_{wire}=\frac{\mu_0 i}{2\pi r}## The Attempt at a...

Homework Statement A thin insulated wire forms a plane spiral of N turns carrying a current ##i##. The inner radius is ##b## an outer radius is ##a##. Find magnetic field at centre of spiral Homework Equations $$B=\frac{n\mu_0i}{2R}$$ The Attempt at a Solution For an area of ##\pi(b^2-a^2)##...

Homework Statement We have an infinite slab of conducting material, parallel to the xy plane, between z = −a and z = +a, with magnetic susceptibility χm. It carries a free current with volume current density J = J0z/a in the x direction (positive for z > 0, negative for z < 0). The integrated...

In a source-free, isotropic, linear medium, Maxwell's equations can be rewritten as follows: \nabla \cdot \mathbf{E} = 0 \nabla \cdot \mathbf{H} = 0 \nabla \times \mathbf{E} = -j \omega \mu \mathbf{H} \nabla \times \mathbf{E} = j \omega \epsilon \mathbf{E} If we are looking for a wave...

Hello, I am having trouble seeing what is going on here and would really appreciate a discussion about the situation. 1. Homework Statement A bar of length ##L = 20 cm## and negliglible mass can slide over two conducting rails connected to a dc generator producing an emf ##V_0 = 6 V##...

Homework Statement Or is it only valid in vacuum condition? Segment of straight wire carrying current I (at distance r) dB = u.Idl x r / 4pi . r^2 (I've came across it on a book about Maxwell's Equations.) Homework EquationsThe Attempt at a Solution Does correction have to be made for...

Homework Statement In a region of space, the magnetic field depends on the co-ordinate ##z## and is given by $$\mathbf{B} = \hat{\jmath} B_0 \cos \left(kz - \omega t \right)$$ where ##k## is the wave number, ##\omega## is the angular frequency, and ##B_0## is a constant. The Electric Field in...

Homework Statement A circular loop of radius R is on the xy plane and the center is at the origin, the current is flowing in a counter-clockwise manner. a) Let Q=(a,0,a) be a point such that a>>R. Find Br and Bθ at Q. b) Let Q=(ha,0,0) be a point on the x-axis such that h<1. Find the vector...

Hi, I'm having an issue with finding a starting point for the following problem. I've looked through my magnetism and electrodynamic notes but was unable to find a starting point. Could someone please help direct me on the correct path? Thank you. Homework Statement A thin circular disc of...

Homework Statement A long solenoid has current I flowing through it, also denote N as the turns per unit length. Take its axis to be the z-axis, by symmetry the only component of the magnetic field inside is Bz. Find the magnetic field at the center of the solenoid (on the axis). Also, find the...

Homework Statement The B field depends on z and t so that ##B = j B_{0}cos(kz-\omega t)## where k is the wavenumber, ##\omega## is angular frequency and ##B_{0}## is constant. The electric field is ##E = E_{x}i + E_{y}j +E_{z}k##. Given ##E_{y}=E_{z}=0##, and ##E_{x}=\frac{\omega B_{0}}{k}## at...

Homework Statement A window, 1.0m by 1.0m receives 27J of energy, from sunlight, in one minute. What is the Rms magnetic field of the light striking the window. Homework Equations E = cB I = (ErmsBrms) / μo The Attempt at a Solution Not sure if those equations are right when solving this...

...perpendicular to its path? OK; let's say you have any charged particle moving perpendicular to a magnetic field; does it describe a gigantic polygon or a perfect circle? I think it's a polygon; the particle absorbs a "quantum of force" from the magnetic field, so to speak, and changes...

Homework Statement A square wire loop of size 2a by 2a lies in the x- y plane with its center at the origin and sides parallel to the x and y axes. A counterclockwise current I runs around the loop. (a) Find the magnetic field on the z axis. [Answer: Bz = 2μ0Ia2/[(a2 + z2)(2a2 + z2)0.5]] (b)...

How strong, approximately, is the magnetic field, on a powerful electromagnet, that you buy on eBay, that can lift, say, a 100 kg?

How does the magnetic field in a Z-pinch develop with time? Does it get stronger and stronger as the pinch contracts? How strong? Where can I read about it on an intermediate or perhaps advanced level? I'm looking for both books and articles. S.A.

Homework Statement A wire is formed into the shape of a square of edge length L. Show that when the current in the loop is I, the magnetic field at point P a distance x from the center of the square along its axis is $$B=\frac{\mu_0 IL^2}{2\pi(x^2+L^2/4)\sqrt{x^2+L^2/2}}$$ Homework...

Suppose we have a Spin-1/2-Particle with no charge, like a Silver Atom, fixed at the origin. The magnetic dipole moment is \mathbf{\mu}=\gamma\mathbf{S}, where \gamma ist the gyromagnetic ration and \mathbf{S} is the spin angular momentum. The magnetic moment creates the magnetic field...

Does magnetic field of lightgets polarised when electric field polarised when passed through a polariser

Homework Statement A straight wire carrying current I goes down the positive y-axis ( I is also in this direction) from infinite y to the origin. At the origin it changes direction 90 degrees and goes along positive x to infinity. Find B at (0,0,z). I'm given that ##\int_{0}^{\infty}...

Dear all, Can anyone give me a time scale/ redshift range as an estimate for the formation of magnetic fields in the universe?

Homework Statement A flexible wire loop has a radius of r = 0.178 m and it is inside a uniform magnetic field of B = 0.332 T. The loop is grasped at points P and Q and stretched until its area is zero. It takes 0.146 s to close the loop. Homework Equations EMF = ∆Phi/∆t Phi = magnetic flux...

I tried to work backwards and verify the magnetic field required by the LHC beam pipes. A circumference of 27km implies a radius R=4300 m. The beam energy E is 7 TeV per proton beam. Considering approximation E approximately equal to pc to get momentum (ultra-relativistic case). Plugging into...

So, assume you have a plasma in a vacuum made of an even distribution of 50% electrons and 50% protons all flowing in one direction with low collision frequency. Then you suddenly turn on an external magnetic field and watch what happens. How will the plasma react? Will the magnetic field...

Homework Statement The figure shows crossed uniform electric and magnetic fields and, at a certain instant, the velocity vectors of the 10 charged particles listed in the table. (The vectors are not drawn to scale.) The speeds given in the table are either less than or greater than E/B (see...

1. The magnetic field at point P due to a magnetic source S1 is represented by ==>. Can a bar magnet S2 be brought close to P so that the total magnetic field at P due to S1 and S2 is zero? Explain your answer.2. None3. Yes, this is possible if both fields at point P have the same magnitude but...

Homework Statement In the circuit shown, two thick copper wires connect a 1.5 V battery to a Nichrome wire. Each copper wire has radius R = 0.009m and is L = 0.17m long. Copper has 8.4 \times 10^{28} mobile electrons/m^3 and an electron mobility of 4.4 \times 10^{-3}(m/s)/(V/m). The Nichrome...

Homework Statement I was reading this textbook: https://books.google.com/books?id=sHJRFHz1rYsC&lpg=PA317&ots=RpEYQhecTX&dq=orbit%20center%20operators&pg=PA310#v=onepage&q=orbit%20center%20operators&f=false Homework Equations In the equation of the page (unlabeled), we have $$...

Homework Statement An electric current is uniformly distributed throughout a long, straight wire that has a diameter of 0.05m. If the current through the wire is 6.0A, calculate the magnitude of the magnetic field: a). 0.02m radially away from the wire center b). 0.05m radially away from the...

Homework Statement A conducting square loop (L × L) moving with velocity vo ay m/s where the magnetic flux density is B=Bo ax Wb/m2 in 0 < y < 2L, and is equal to zero when 0 > y and y > L. Determine the current in the loop and plot its magnitude as a function in the loop's position in the...

I've having trouble understanding one of the consequences of using the length gauge. The length gauge is obtained by the gauge transformation ##\mathbf{A} \rightarrow \mathbf{A} + \nabla \chi## with ##\chi = - \mathbf{r} \cdot \mathbf{A}##. Starting from the Coulomb gauge, we have $$...