B field Definition and 173 Threads

[credit to wikipedia] So it would appear that the type 1 meissner effect allows for the localized increase of magnetic flux density (as the displaced field must go somewhere, the B field is somewhat larger at the surfaces of the superconductor then elsewhere, and in fact is a higher value...

imagine a metal rod floating in a region of magnetic field. You give the rod a slight nudge. Will the rod continue to go forever? Considering conservation of energy i think it wouldn't. But i can't come to terms with any reasonable reasoning.

I was under the impression that it does, you know from Ampere's law. But today, my professor told me that Electric and Magnetic fields are very similar (although I can't imagine they are exactly the same, since there are no magnetic monopoles), THAT a non-time dependent E field does not create...

I am doing an experiment to measure the charge to mass ratio of an electron. And I have found the method suggested by Thompson to account for the effect of the Earth's magnetic field[http://ajp.aapt.org/resource/1/ajpias/v58/i10/p1019_s1?isAuthorized=no" ]. But it only gives the equation, i.e...

If I wanted to make bar magnets would I heat up the metal and then place it in a B field of a solenoid and then cool it down in the field to keep the magnetization? It seems if i heated it up first the atoms would be more easily aligned in the B field, And then cool it down to preserve this state.

My professor had an example in class the other day where we had an infinite line of current uniformly distributed over a circular wire with radius R. He wanted to look at the energy of the B field produced by this current. He did the normal thing and integrated 1/2u*B^2 over all space. It...

Hi. New to the forums so bear with me. I am trying to calculate the magnetic field at a distance r from a wire carrying a 495Hz signal at 8Vpp and current 0.8mA. Initially I tried ampere's law, but fell into the trap of using the un-modified form (without maxwell's correction). I know that...

Homework Statement In a plastic film factory, a wide belt of thin plastic material is traveling between two successive rollers with the speed v. In the manufacturing process, the film has accumulated a uniform surface electric charge density σ. What is B near the surface of the belt in...

Why do materials like aluminum cut down the value of the B field? Like suppose we had an infinite current carrying wire wrapped with a cylinder of aluminum. To find the B field we would use amperes law and the magnetic susceptibility of aluminum. For example, when a superconductor is...

Homework Statement A 40 turn square coil has an area 11.0 cm2 and is rotated with an angular speed of 110.0 rads in a uniform 1.00 T magnetic field. The axis of the coil is perpendicular to the field at all times. (i.) What is the frequency of the sinusoidal voltage induced across its...

What happens if I place a solid conductor in a static B field. I mean B fields can't do work so it won't induce a current unless its a superconductor. Will it shift the electron orbitals because of the Lorentz force? Any input will be much appreciated.

Homework Statement In a particular experiment, a particle of mass m and charge +q moves with speed v along the x-axis towards increasing x. Between x = 0 and x = b there is a region of uniform magnetic flied B in the y-direction. Deduce the conditions under which the particle will reach the...

Homework Statement Particles with charge e and mass m are emitted with velocity v from a point source. Their directions of emission make a small angle with the direction of a uniform constant flux density B. Show that the particles are focussed to a point at a distance 2pi mv/Be from their...

Homework Statement Particles with charge e and mass m are emitted with velocity v from a point source. Their directions of emission make a small angle with the direction of a uniform constant flux density B. Show that the particles are focussed to a point at a distance 2pi mv/Be from their...

Apologies if this is not in the proper location/format/etc; first post. In a very short (3 min) segment on MythBusters, they unsuccessfully tried to induce a current in a loop in the same plane as a current carrying wire (AC). I originally assumed this didn't work because the B field was not...

In classical physics when we have a current we have a B field. So let's say we have a charged wire and then we apply a voltage and then current starts to flow. What happened when the charge was stationary and then moving to cause this B field. When the charge is at rest it has an E field, but...

I have read different light frequncies have different lensing characteristics. Example, Gamma frequencies not capable of being focused with a lens. This made me think, what happens to E and B fields, for visible spectrum, when you focus photons with a lens? Anything? Do the fields distort...

Homework Statement how to find B field in parallel plate capacitor the plates have a length L and width w and separated a distance h Homework Equations B dl=\mu I The Attempt at a Solution I am trying to find the B files i thought u would use B dl=\mu I but the book has the...

Is the B field constant inside a toroid? Like we would just use amperes law to find. B(2*pi*r)=(mu_0)NI But after talking to this kid he said it changes inside. But i thought it was constant.

Homework Statement We have 2 circular loops, each of radius R with current I in same direction. This is called a Helmholtz coil. The loop axes are along the z axis and the centers are at z=+/-s/2. Find the magnetic field along the z axis between the 2 loops. Homework Equations...

Homework Statement A solenoid 2.50 cm in diameter and 30.0 cm long has 300 turns and carries 12.0 A. Calculate the flux through the surface of a disk of radius 5.00 cm that is positioned perpendicular to and centered on the axis of the solenoid. Homework Equations B = (permeability...

When I have an infinite solenoid , The b field lines point straight up the solenoid and the field is zero outside. But i thought that the field lines have to wrap back around on themselves. Does this not apply in this example . Or am i crazy?

Homework Statement Magnetic field in xz plane. \vec{B}=\hat{i}B_x+\hat{k}B_z Write down the hamiltonian operator for the interaction of the electron's intrinsic magnetic moment with this field and express it in matrix form. Find its eigenvalues and sketch these as a function of Bz...

Homework Statement A wire hoop is placed in front of a strong magnet, with the magnetic field B=1.1 T, pointing as shown. The strength and direction of the magnetic field are constant through the loop. The sides of the hoop have a track in which a copper wire of length 9.1 cm and mass 25 g, is...

Homework Statement Two concentric circular loops of wire carrying current in the same direction lie in the same plane. Loop 1 has radius 1.8cm and carries 3.6 mA. Loop 2 has radius 2.3cm and carries 6 mA. Loop 2 is to be rotated about a diameter while the net magnetic field set up by the two...

My end goal is to analytically or numerically calculate the magnetic field inside and around a square conductor that has connection points at the top and bottom with a voltage applied. Are there any software packages (mathematica, or even just C) that can do this given ANY current density in...

Why does the Brewster angle phenomena happen only when the electric field vector lies in the plane of incidence (the magnetic field vector is perpendicular to that plane) but not when the magnetic vector field lies in the plane of incidence (now the electric field is perpendicular to that plane)?

Hi, In the Purcell book on E&M that we used during college (berkeley physics course volume 2), the b field of a current carrying wire was explained as the result of a relativistic transformation between two frames of reference... The explanation in purcell seems to require the...

Homework Statement Electron shot in x direction with V_o=3.5*10^6 and is accellerated thru parallel plate capacitor with potential difference of 70V. after it travels on the x-axis for 5 mm what is its total field the electron produces? including magnetic and electric. Show direction and...

I know the results for infinite, but how about finite? And where is the cutoff with the aproximation of infinite? I've heard the value 10% tossed around is that right?

1. Magnetic resonance imaging needs a magnetic field strength of 1.5 T. The solenoid is 1.8 m long and 75 cm in diameter. It is tightly wound with a single layer of 2.20-mm-diameter superconducting wire. 2. B = mu0BI / l 3. Is there a way to do this without finding N? Either way...

Preface: If a bar magnet is cut in half, we are left with say N-S--cut--N-S allinged along the z axis. Then the S and N ends are attracted to each other. This attraction is due to the "fringing" or non-uniform B field of the poles. That is the component of the B field that is normal to the...

Homework Statement The magnetic field inside a 5.0-cm-diameter solenoid is 2.0 T and decreasing at 4.90 T/s What is the electric field strength inside the solenoid at point on the axis?Homework Equations E=(r/2)*(dB/dt)The Attempt at a Solution E=(.025/2)*(4.9)= 0.06125 V/m Not sure what's...

Does a straight wire in changing B field(the field is perpendicular to the wire) has an induced emf?

Homework Statement (a) If the resistance of the resistor in the figure below is slowly increased, what is the direction of the current induced in the small circular loop inside the larger loop? (b) What would it be if the small loop were placed outside the larger one, to the left? Homework...

As in Feynman's lecture on physics vol 2, he showed that the "true energy" of a magnetic dipole(current loop) in an external B field is m*B, not -m*B. Basically the argument is if you want to pull a current loop from infinity to the final position, you must do extra work to keep the current in...

Homework Statement Use a thermodynamic argument to show that a strong magnetic field will cause a transition from a super-conducting to a normal state. Homework Equations The Attempt at a Solution Most books seem to use, the fact that the gibbs function of the super-conducting...

Homework Statement A box of wire is moving within a constant B field. Is there an induced current? Homework Equations Slap rule The Attempt at a Solution Since the wire is experiencing constant B field, how would we figure out whether or not there is a current? I know there is a...

Greetings, In Feynman's lectures - vol. 2 either chap 19, 21 or 23 - I think 23 (I'm at work and don't have the lectures here), Feynman shows in a capacitor that a changing E-Field induces a B-field, then he shows that the B-field induces a new E-Field (he calculates the E-field) and then...

If I have bar magnet made of anti matter is the B field the same as regular matter and would their north poles repel and so on ?

Suppose you have an axially symmetric magnetic field for which the azimuthal component B_\phi = 0. This is all you know. What are some possible vector potentials \vec A (such that \vec B = \nabla \times \vec A) that would produce this field? (So we're working in cylindrical coordinates.) The...

Homework Statement Assume that an electron of mass m and charge magnitude e moves in a circular orbit of radius r about a nucleus. A uniform magnetic field B is then established perpendicular to the plane of the orbit. Assuming also that the radius of the orbit does not change and that the...

Homework Statement I need to find the magnetic field a distance r from a long, thin wire carrying a current I(t) = I_0 \sin \omega t.Homework Equations Field a distance r from a wire carrying a steady current I in the z direction: \vec B(r) = \frac{\mu_0 I}{2 \pi r} \hat \phi The Attempt at...

Homework Statement An electron of mass Me, with charge -e, is in a circular orbit in the xy-plane. There is a uniform magnetic field B in the positive z direction. It is moving at constant velocity V. Working in CGS units... Find R in terms of Me, -e, v, and B Find the angular...

Homework Statement A beam of ions enters a region in which the electric field E and magnetic flux density B are normal to each other and both normal to the velocity of the ions. Show that if the velocity of the ions is related to the fields by v=ExB/B2 then the ions pass through the...

A region of space d = 35 cm wide is filled with a uniform magnetic field B = 2.3 T oriented normal to the plane of the screen and pointed into the screen. There is no magnetic field to the left or to the right of this region. An external agent drags a rectangular conducting loop with dimensions...

I was curious, if the same voltage was applied to two conductors, I guess wired in parallel, and both passed through a magnetic field at a right angle to the field, and one was refrained from moving, while the other was allowed to move - which path would the electrical current travel?

Homework Statement A wire ring lies in the xy-plane with its center at the origin. The ring carries a counter clockwise current I. A uniform magnetic fireld B is the the +x direction. There are a few parts to the question (Note: Everything except for I is a vector): 1. show that dL =...

Why is the b field inside a thick toroid largest along inner edge and smallest along outer edge?

Homework Statement the current density is given by J(p) = (I/pi) * p^2 * e^(-p^2) in z direction The question is to first show that the cureent flowing through the wire is 'I' and then to find then to find the B field. Homework Equations stokes theorem. integral of B.dl = I I =...