Magnetic fields Definition and 674 Threads

what are electric and magnetic fields? i know that theyre constant exchanges of virtual photons but what properties do each have and what's an example of a change of perspective where an electric field becomes a magnetic field and/or vice versa

I know that \int_{S}^{}\int_{}^{}\vec{B}\cdot d\vec{A} = 0 because \textbf {div} \vec{B}=0 IE, because \Phi_{B} leaving a closed surface must equal \Phi_{B} entering. Yet how is it then that \int_{C}^{}\vec{B}\cdot d\vec{l} isn't also equal to zero? Shouldn't it be true for any...

Hi, I'm looking at question #33 of the linked book on page 391. http://books.google.ca/books?id=4fXFO-0B6f4C&pg=PA391&lpg=PA391&dq=zero+magnetic+fields+proof&source=bl&ots=ZmVev2Wdpb&sig=_P2-p3xN29sgIKC3aNsp8N15xCo&hl=en&ei=ExrUSaukIIWsnAfRteDzDg&sa=X&oi=book_result&ct=result&resnum=1 I...

ok guys so i have two questions, i need help on two questions on the following site "[URL /AP%20Physics%20Daily%20Problems/AP%20Daily%20Prob%20131-140.pdf"]http://staff.hartdistrict.org/glyle/ap_physics/Homework /AP%20Physics%20Daily%20Problems/AP%20Daily%20Prob%20131-140.pdf[/URL] they...

Homework Statement A long, straight wire carries a current of 14 A. Next to the wire is a square loop with sides 1.0m in length. The loop carries a current of 2.5A in the same direction as the wire. Calculate the net force acting on the wire. Homework Equations Magnetic Field for...

1. I have read that external magnetic fields cannot penetrate a superconductor. Why is this? 2. Does the magnetic field produced by the superconducting current extend outside of the superconductor? And if so, what happens when the magnetic field starts to collapse, can it renter the...

Since neutrons have no electric charge, how is it that a neutron star is able to produce a magnetic field? :confused:

Homework Statement An electron is moving through a magnetic field whose magnitude is 8.70 X 10-4 T. The electron experiances only a magnetic force and has an acceleration of magnitude 3.50 X 1014 m/s2. At a certain instant, it has a speed of 6.80 X 106 m/s. Determine the angle \theta (less...

Homework Statement Your friend wants to be a magician and intends to use Earth's magnetic field to suspend a current-carrying wire above the stage. He asks you to estimate the minimum current needed to suspend the wore just above Earth's surface at the equator (where the Earth's magnetic field...

I have a physics exam tomorrow and while recapping things for the exam, I was wondering one thing. The magnetic force exerted to a current carrying wire in a uniform magnetic field is \vec{F}=I \vec{l} \times \vec{B}. But a current carrying wire induces a magnetic field, so the magnetic field...

Homework Statement The drawing shows a parallel plate capacitor that is moving with a speed of 31 m/s through a 4.0 T magnetic field. The velocity v is perpendicular to the magnetic field. The electric field within the capacitor has a value of 170 N/C and each plate has an area of 7.5...

Is there a material that blocks or reflects magnetic fields such as a field from a neodymium magnet?

Alright. I don't understand the fundamental quantum basis behind the attraction of two magnets. My book notes that magnets manifest themselves when a material such as iron has unpaired electrons in orbitals that spin in the same direction. If an electron is paired, the electrons will spin in...

Homework Statement http://www.aijaa.com/img/b/00125/3627010.jpg http://www.aijaa.com/img/b/00758/3627011.jpg Homework Equations E_k=\frac{1}{2}mv^2 \vec{F}=m\frac{\vec{v}^2}{r} \vec{F}=q\vec{v} \times \vec{B} \frac{v}{r}=\frac{2\pi}{T}=\omega The Attempt at a Solution The...

Homework Statement A beam of protons is accelerated to a speed of 5.0x10^6 m/s in a particle accelerator into a uniform magnetic field. What B field perpendicular to the velocity of the proton would cancel the force of gravity and keep the beam moving exactly horizontally? Homework...

HI all: I have one confused question. a infinitely long wire carrying constant direct current is placed in the space. One particle with charge q and velocity v is moving in the magnetic field which is created by current-carrying wire. We know in the lab frame. particle will accelerate in this...

Can anyone explain why these two field patterns are so similar? The (3,2,1) hydrogen wave function, and this pattern generated from a magnet on a CRT. (attached to post)

When electricity flows through a coil of wire, what does the resultant magnetic field resemble? a the magnetic field of a bar magnet b the magnetic field of a horseshoe magnet c the magnetic field around a straight wire d the magnetic field around a circular magnetic disc. ok so i know...

Homework Statement Two point charges, -520x10-6C and -270x10-6C are 2 meters apart. At which point would a carbon nucleus experience zero net force? (positive test charge) Homework Equations k=9x109 F=k((q1*q2)/r2) Coulomb's Law E=k(q1/r2)=(F/q2) The Attempt at a Solution I really...

Homework Statement I don't quite understand the following question, i get a very unrealistic result... The write head of a hard disc drive produces a magnetic field of 95mT. The disc has a radius of 3.5 inches and rotates at 7200 rpm (rotations per minute). Calculate the Lorentz force...

Homework Statement The problem is as seen in the attachment.Homework Equations T(torque) = (N)(I)(A)(B)(Sin(theta))The Attempt at a Solution For this question I used the above formula to find the magnitude of the torque, but what I am not sure about is which orientation would produce the...

I was wondering if there where any ideas or theories regarding what a magnetic field is composed of. Are there any particle ideas, or is it just something we don't understand yet

I have a simple question here that I seem not to be able to figure out. If you have a regular bar magnet, it emits a magnetic field around it. So, if you create an experiment and found out how far that field reached, you would see that the field doesn't go very far. Maybe like 3 inches (~...

Homework Statement Which two of the three types of fields in the title of this are thread are the most similar? Provide supporting evidence? Homework Equations Gravitational: -Source: point mass -Field intensity proportional to: M/r^2 -Range: long range -Strength: weak -Direction of field...

A parallel-plate capacitor, C=5 mircoF, has closely spaced circular plates of radius R = .1m. How much displacement current is encircled in a loop of r=.05m that is centered on the axis between the plates when a uniform electric field between these plates changes with time at the rate of...

http://www.sciencedaily.com/releases/2008/12/081202081449.htm ScienceDaily (Dec. 3, 2008) — The sun’s magnetic field may have a significant impact on weather and climatic parameters in Australia and other countries in the northern and southern hemispheres. According to a study in Geographical...

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...

Homework Statement If a current of electrons flow through the conducting wire from south to north, in which direction will the compass deflect. a)west b)east c)north d)southHomework Equations None are necessary. The Attempt at a Solution I think the answer is west, because using the left...

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...

This isn't a homework problem, but I figured I'd post it here since it's a pretty basic question, in my view at least. So my professor and Senor Griffiths have been telling me this for the past year. Cool. Now I'm working on a project that uses a superconducting magnet. So I started to...

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