Magnetic fields Definition and 674 Threads

[SOLVED] Magnetic Fields, Deuterium and curved tracks Homework Statement A deuteron (the nucleus of an isotope of hydrogen) has a mass of m_D and a charge of e. The deuteron travels in a circular path with a radius of r in a magnetic field with a magnitude of B. Find the time required...

Hey all, Having stumbled across this forum completely by accident I thought I would stay for a while. As such I have a question. Would a black hole have a magnetic field? I would assume that magnetic fields are affected by gravity and therefore any magnetic field would be destroyed when...

Hi, I'd like to visualize magnetic fields between magnets and charges. Fieldlines/streamlines would be ideal but e.g. vector arrows would do too. Although a 3D model would be perfect, any advice regarding 2D approaches is appreciated as well. Do you have any tipps on how to accomplish...

Magnetic fields (urgent) Hello, I'm in trouble, I have no idea what to do/look for the formula to solve these 2 questions. Please help and guide --------------------------------------------------------------------------------- A straight wire has a current of 15 A vertically upwards, in...

Homework Statement Prove that the time for one revolution of a charged particle moving perpendicular to a uniform magnetic field is independent of it's speed. Write an expression that gives the period T in terms of the mass and charge of the particle and the magnetic field strength...

Two very long fixed wires cross each other perpendicularly. They remain infinitely close together but do not touch and remain electrically isolated from each other. Equal currecnts flow in each wire. Indicate the locus of points in the plane containing the wires where the net magnetic field is...

Homework Statement Two long straight wires sit at the lower corners of an equilateral triangle and carry current I. Find the magnitude and direction of the B field at the top vertex of the triangle for the case where: a) the current in both lower wires flows out of the page b) the...

[SOLVED] A question about Magnetic Fields and A Charge A charged particle enters in 90 degrees to the magnetic field i.e. the force on the charge is F = qvB as sin (angle) = 1. The question is which are the effects on the kinetic energy and momentum of the particle? Alternatives: A. KE...

Okay, I am in AP physics this year at my high school. We are doing E&M (Electro Magnetism) right now and I have a question that my teacher could not answer (who by the way is quiet possibly the smartest person I have ever met). Okay, I understand that a charged particle moving perpendicular...

surely \vec{\nabla} \times \vec{B} \neq 0 in general but the work done by magnetic field on any charge is 0 hence is independent of the path taken So can we call such a field conservative

Homework Statement at time t1, an electron is sent along the positive direction of an x axis, through both an electric field E and a magnetic field B, with E directed parallel to the y axis. Figure 28-34 gives the y component Fnet, y of the net force of the electron due to the two fields, as a...

So I am somewhat confused on magnetic fields. Do they have a charge? Because I have come across many problems that involve either protons or electrons and whether or not they are deflected by the field. My question is if the fields do have a positive or negative charge, how are you suppossed to...

Homework Statement The force on a wire .80 m long that is perpendicular to the Earth's magnetic field is .12 N. What current flows throught the wire? (Earth's magnetic field is 1.0x10^-4 T at the poles and 5.0x10^-5 T at the equator) Homework Equations Fm=BIl Fm is magnetic force in N...

Homework Statement IF we consider electrons in a crystal subject to a magnetic field. The electrons near the fermi energy wil obey open or closed orbits. Using semiclassical eqn of motion and band structure for a bravais lattice, discuss the behavour and derive all conserved quantities...

[SOLVED] magnetic fields and torque so for this question, i have an inclined plane with a coil of wire wrapped longitudinally around a cylinder N turns. the plane of the coil is parallel to the inclined plane with a uniform magnetic field they want me to find the least amount of current...

I was just wondering, since my textbook doesn't really explain it too well, what velocity is part of the equation F = qv x B? Is it the drift velocity, or...?

Homework Statement 12.5A, 3.1x10^-5 Homework Equations How far from a long conductor passing a current of 12.5A is the magentic field of strength 3.1x10^-5T? The Attempt at a Solution B= uI/2(pi)r r=uI/2(pi)B =(4pi)(12.5A)/ 2(pi)(3.1x10^-5T) = 8.1x10^5m

Homework Statement An elastic conducting material is stretched into a circular loop of 20.0 cm radius. It is placed with its plane perpendicular to a uniform 0.900 T magnetic field. When released, the radius of the loop starts to shrink at an instantaneous rate of 78.0 cm/s. What emf is...

...||==|| .||...|| ||... 0...|| ..||...|| ...||==|| This is a really bad picture, but it should kind of give the idea. How do I deal with a system where a current is running in a cylinder surrounded by a cylindrical shell? I know this sounds like a homework question, and it is related to...

A long, straight wire is oriented in the north-south direction, and the current in the wire is directed to the north. The horizontal component of the Earth's magnetic field is 4.5 x 10-5T and points due north. A small horizontal compass needle is located directly below the wire, 1.9 cm from it...

Homework Statement A loop of wire is at the edge of a region of space containing a uniform magnetic field B. The plane of the loop is perpendicular to the magnetic field. Now the loop is pulled out of this region in such a way that the area A of the coil inside the magnetic field region is...

I put this in the intro forum about 3-4 hours ago and no one answered, can anyone here help? 1. Homework Statement An experiment on the Earth's magnetic field is being carried out 1.00m from an electric cable. What is the maximum allowable current in the cable if the experiment is to be...

I know this is technically a planetary science question rather than astronomy but this still seemed like the best forum to ask it in. Do we know why planets have magnetic fields? Does it have anything to do with conductive matter content or ferrous / metallic content? Do purely silicate...

This guy seems to have done something like that: http://gizmodo.com/361390/1301-florescent-bulbs-lit-solely-by-magnetic-fields Now.. what i was thinking is that.. how could he have done that? The power lines carry alternating current all right and it's a changing current, so it produces a...

\nabla \cdot B=0, so \int\nabla \cdot B dv=0, then \int B \cdot \widehat{n}da=0, let B=\nabla \times A, then \int\nabla \times A \cdot \widehat{n}da=0, thus A=\nabla\varphi[/itex], thus [tex]B=\nabla \times A=\nabla \times\nabla\varphi=0 I know something is wrong with that but I am not sure...

Maxwell's equations give that the electric and magnetic fields in E-M radiation are orthogonal. This is a classic equation, but can it be related to the orthogonality of, for example, the momentum and position operators which lead to non-commutivity?

1. An ionized deuteron (a particle with a + e charge) passes through a velocity selector whose perpendicular magnetic and electric fields have magnitudes of 40 mT and 8.0 kV/m, respectively. Find the speed of the ion 2. When a charge particle moves in a velocity selector, both electric...

http://www.centreforthemind.com/publications/SavantNumerosity.pdf"

I'm studying a QFT course, and we've been asked to consider why classical physicists found it useful to introduce electric and magnetic fields, but not fields for electrons or other particles. I'm completely stumped, and would appreciate any hints. thanks

Hi! I am new user to this forums and on the start I have one question: "If I increase the speed of the electrons, will the magnetic field strength of the electrons increase? Thank you.

hello I was hoping someone could tell me a way to show my children a way to see a magnetic field?they are playing with magnets and don't underststand the way i explained how they work . if i could show them they might start to understand ... thanks in advance for your reply

The magnetic fields of several planets in our solar system are from what I've read caused by electric currents - does anyone know what the electric currents are caused by?

Homework Statement The north end of a bar magnet is pushed downward toward a wire loop in the plane of the paper. In which direction is the induced current, and which way is the induced magnetic field? A. clockwise, into the paper B. clockwise, out of the paper C. counter-clockwise...

Magnetic Field on an incline This is what looks to be a fairly simple magnetic field problem, but I don't have much experience in relating velocities to electrical currents, so I'm a bit stuck. The problem as described is So my variables to my knowledge are I = unknown m = 0.19 kg B =...

I know high magnet fields can be dangerous to health. My questions are 1) at what point does a magnetic field become powerful enough to be actually cause problems with human health and 2) why exactly is it hazardous at high levels? Thank you for your time.

As described in this report, the limits on the strength of stable magnetic fields are due to the magnetic forces on the conducting elements that tend to tear them apart: Magnetic Radiation Shielding: An Idea Whose Time Has Returned? Geoffrey A. Landis "The limit to the mass required to...

Homework Statement Calculate the magnetic field required to produce a deflection of .20 radians in Thomson's experiment. Assume the potential across the deflection plate is u=200V, the length of the deflection plates is x=5.0 cm, and their separation d=1.5cm. Compare this value of B to the...

Hello, I was wondering, how exactly do magnetic fields interact? Say if you have 2 permanent magnets, 1 perhaps of 0.3T and another of 0.5T and you let the N and S attract so they clamp together, would the resulting field of the combination have 0.5T on both ends (i.e. would the surplus...

Ok this may be a silly question, but I have trouble grasping the function of the inverse square law and how it relates to the intensity of a magnetic field. It seems to me that if we take the same calculations of I2 = (I1 * D1^2) / D2^2 we come up with different real world answers based on...

A charged particle of mass m and positive charge q moves in uniform electric and magnetic fields, E and B, both pointing in the z direction. The net force on the particle is F=q(E+v x B)*. Write down the equation of motion for the particle and resolve it into its 3 components. Solve the...

If you were to take a superheated iron ball (say a heavily scaled down version of the Earth's core) and set it in motion inside of a heated and ultra-pressurized plasma globe with another light hard coating ontop of it also set in motion, would that generate a magnetic field similar in shape to...

I have a cluster of magnetic sources around a volume and I need to know the real magnetic field in a point (namely x_0) inside the volume by measurements in another point x' in the surface of the volume. I'm getting mad

Hi, The following is the standard qualitative explanation of the duality between electric field and the magnetic field given in our textbooks: Let a long straight wire carry a constant current i. A charge kept at rest near it does not experience any force, implying the absence of electric...

I started asking this question after one of my students had trouble with a problem asking for the net force on a current loop in a homogeneous magnetic field (on my first day of TAing, no less!). A current loop in a magnetic field will experience a torque, but not a net force. I always assumed...

I just have some questions about this stuff... How can the nature of a material determine if it can be made into a magnet? Whats the field around a straight conducter look like? Whats the direction of the magnetic field of a soleniod? Whats the action of a relay? How are the...

Ok can anyone tell me how the nature of a material determine if it can be made into a magnet? Can anyone illistrate any ne of these to me - the field around a straight conductor - the magnetic field direction of a soleniod -the action of a relay how was the telephone developed...

The question is a bit disingenuous. My real question is: How powerful would a magnetic field need to be to emit photons that fall in the visible spectrum - if that even makes sense. I know that magnetic force and electrical force are the same force: electromagnetism is transmitted by photons...

Question solved!

Homework Statement A charged particle enters a uniform magnetic field and follows this circular path: http://img257.imageshack.us/img257/781/physsk4.png Questions: 1: Is it positively or negatively charged, or is it electrically inert? 2: Why? Homework Equations None. The...

Are there any materials out there that can reflect magnetic fields, or can a twisted channel be formed for them to follow?