Magnetic fields Definition and 644 Threads

This question was on my homework and I don't really understand how it has to do with magnetic fields. Homework Statement As 2 parallel conductors with currents in the same direction are moved apart, their force of A) repulsion decreases B)Repulsion increases C) attraction decreases D)...

Homework Statement Figure a below shows two concentric circular regions in which uniform magnetic fields can change. Region 1, with radius r1 = 1 cm, has an outward magnetic field 1 that is increasing in magnitude. Region 2, with radius r2 = 2 cm, has an outward magnetic field 2 that may also...

Homework Statement Problem 1 If all of the particles shown in the figure are electrons, what is the direction of the magnetic field that produced the indicated deflection? http://session.masteringphysics.com/problemAsset/1013281/5/jfk.Figure.24.Q35.jpg Choices Up (toward the top of the...

Homework Statement A circular 10 turn coil that has a radius of 0.05 m and current of 5A lies in the xy plane with a uniform magnetic field B = 0.05 T i + 0.12 T k (i and k are the unit vectors). What's the potential energy for the system? Homework Equations U = -m*B where m is the...

Homework Statement I was wondering how would you determine the magnitude an external field needed to cancel two magnetic fields in two wires? In this instance the currents of the two wires are in opposite directions...so I know there is a repulsion force. The currents in both wires are equal...

Greetings. I've been doing some things for the past couple of weeks just for fun, but I have no way of knowing if I'm on the right track or not, so if anyone is willing to take a glimpse, feel free to point out any errors or say harsh thing, or throw tomatoes at me, because I need some...

Hi everyone, 1. Part (a) Find the magnetic field above and below an infinite current sheet (infinite straight wires with current I along the positive z-axis). The sheet is on the xz plane. There are N wires per meter counting along the axis. Part (b) There are two parallel sheets with...

I can't seem to find any real information on this, so maybe this is the place to get it. Ok, we know Superconductors repel magnetic fields. We know anything with current running through it produces a magnetic field according to the right hand rule. Obviously this is how superconducting...

I'm a new teacher to E&M and confess I was a lowly Chemistry Major who needs some help. A proton and a particle of equal mass without charge are somehow provided equal energy directed, at least at onset, in the form of translational energy. Will the uncharged particle move faster because...

Homework Statement calculate a value for B at a distance of 50cm, in ,air, from a long straight cable carrying a current of 1000A. Homework Equations F=Bqv=BIl I=q\t = qv/l F=LIB The Attempt at a Solution i have not been able to calculate an answer as there are constantly two...

I have several texts, some new, some from the turn of the 20th century, that are all packed with explanations and formulae for electromagnetic theory. In almost all of them, it is stated that the magnetic field or it's lines of flux, are an abstraction, a mathematical tool to aid in solving...

Homework Statement Wut force will the rod that rests on the 2 parallell rails feel when the battery switch is closed http://s336.photobucket.com/albums/n343/physicsdude69/?action=view&current=phys2.jpg a. to the right b. out of the page c. to the left d. into the page Homework...

Hello, i just got done ranting on Q#1 (its in another post, and I am still in a ranting mode) and was about to go to bed for the day, when i figured "well heck i have been working on these 2 questions for 9 hours and have made almost no progress, asking the people in my class for help is like...

Hello, this is my 1st time asking a question. May I have some assistance? I will just copy and paste the question so that I don't mess up anything Homework Statement A single-turn circular loop of radius 0.08 m and resistance 6 is coaxial with a solenoid of length 90 cm and a radius of...

Homework Statement Due to friction with the air, an airplane has acquired a net charge of 1.70 multiplied by 10-5 C. The plane moves with a speed of 2.80 multiplied by 102 m/s at an angle θ with respect to the Earth's magnetic field, the magnitude of which is 5.00 multiplied by 10-5 T. The...

Homework Statement Determine the initial direction of the deflection of charged particles as they enter the magnetic fields as shown in Figure P29.1 (attached). Homework Equations I don't think there are any. The Attempt at a Solution I believe this problem will need to make...

Homework Statement A system consists of N pairs of non-interacting, spin 1/2 particles with magnetic moment \mu. It is initially immersed in a uniform magnetic field H_{i} while it is in thermal equilibrium with a reservoir at temperature T_{i}. While remaining in thermal equilibrium with the...

Homework Statement An coil has 4000 turns of wire and a mean area of cross-section 25cm^2. A magnetic field of flux density 0.16T passes through it. When the magnetic field is reduced steadily to zero in 0.0050s, emf is induced across the terminals of the coil. Calculate the value of this...

Unfortunately, magnetic fields are by their nature invisible, but scientists from NASA’s Space Sciences Laboratory have managed to put on film what these natural phenomenons would look like if we could see them with our own eyes. Please note that this is a simulation and has been created using...

http://gizmodo.com/5012347/nasa-scientists-make-magnetic-fields-visible-beautiful http://gizmodo.com/assets/images/gizmodo/2008/06/magnetic_movie_1.jpg

Hi Everyone seems to know what magnetic fields are and that they are caused by electric currents, but i can't seem to find a good reason WHY they are caused by lectric currents. Thanks, appreciated

Hi Everyone seems to know what magnetic fields are and that they are caused by electric currents, but i can't seem to find a good reason WHY they are caused by lectric currents. Thanks, appreciated

[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...

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