Magnetism Definition and 952 Threads

I've seen in feynman and on the internet a derivation that the force on a negatively charged particle from neutral current carrying wire can be shown to be purely magnetostatic in one frame of reference and purely electrostatic in the other frame of reference using the length contraction. The...

I just saw an instructor of EEE (YouTube) talk about Cross Product. He gave an example of when cross products are used. Here's what he said. He drew a vertical arrow and said this is current. Then he drew a circular arrow around the vertical line and said it is B. Then he drew a smaller...

What if i was traveling in a car with an e- with me. W.r.t to a positive charge at rest , it would seem accelerating to me i.e. it would have a magnetic field but acc. to a person on the ground it would just have an electric field. If there were a car moving relative to me , the person would...

Have always wondered this so maybe I can get an answer here: when a large industrial electromagnet is switched off and the electricity-produced magnetism ceases, is there a small amount of residual magnetism in the uncharged electro-magnet? If so, does it dissipate according to a established...

Why is it that 2 wires carrying parallel current attract each other i think they should repeal imagine 2 wires carrying electrons to the left then the current is to the right, in the reference frame of the moving electrons it seems like the electrons on the other wire are not moving so the...

I need an explanation that relates the equation to what I learned about the dot product of two vectors being the magnitude of the parallelogram formed by the two vectors in 2D or similarly by the paralleliped formed by three vectors in 3D. I want to know for instance if the resultant is...

Please consider the following… Suppose you were on a space-walk at the International Space Station and you had two refrigerator magnets. And suppose you gently released one magnet so that it remained “stationary” in space. And suppose you threw the second magnet as hard as you could in the...

Homework Statement Two small objects, labeled 1 and 2 in the diagram (see link), are suspended in equilibrium from strings of length L. Each object has mass m and charge +Q. Assume that the strings have negligible mass and are insulating and electrically neutral. Express all algebraic...

Homework Statement Two long thin parallel wires 13.0 cm apart carry 25 A currents in the same direction. Determine the magnetic field at point P, 12.0 cm from one wire and 5.0 cm from the other. (Sorry I don't have a diagram, but this is essentially a triangle, with sides of 13 cm, 12...

A 1.0 E -6 F capacitor has a charge of 10.0 micro C. It is connected to a 1.0 H inductor at t = 0. Compare the potential energy of the capacitor to the potential energy of the inductor at t = 10s. Which energy is greater?

Homework Statement Two 1m long current carrying wires are separated by 0.05m. One carries 2A and one carries 3A. What is the magnitude of the mutual force between them? In what direction does the force act on each wire? Homework Equations The Attempt at a Solution I apologize for not...

I read recently that magnetism plays an important role in cramming all that matter into a black hole. But how is it possible that magnetic force could escape a black hole, having an escape velocity higher than the speed of light, therefore an impossibility of matter(or energy) escaping?

My physics book says that the magnetic field is caused by moving electrical charges, acts only on charges with a motion vector perpendicular to itself, and the force it exerts on a charge is proportional to the velocity of the charge. How does the moving charge cause this force, which does not...

I was reading Michio Kaku's book Prallel Worlds recently and I believe I saw it say that Maxwell's equations for electricity and magnetism become the same for electricity and magnetism when monopoles are introduced. My question is, if the equations become the same then why don't we say that...

Hey, first of all, I wanted to know that if you pass an electric current through an iron rod, for example, then what would be the relationship of it's electric field and magnetic field? Will they be parallel to each other or perpendicular?:confused: Second: suppose to fire a particle, let it...

Magnetism problem for General Physics 2! Homework Statement Suppose the rod in the figure has mass m= 0.40kg and length 20cm and the current through it is I= 40A . (Intro 1 figure) If the coefficient of static friction is us= 0.55, determine the minimum magnetic field (not...

Homework Statement The points A,B,C are the vertices of an equilateral triangle, of side L. Two equal positive charges q are at A and B. A)Find the electric potential at C assuming V=0 at infinity B) Give the expression for the work necessary to bring a positive charge Q from infinity to C...

Homework Statement Show the mathematical relationship between magnetism and electricity by looking at constants Homework Equations I have several equations but in don´t really know which one I have to use and I don´t see any big similarities except that there is force, charge, velocity...

Hello, The Lorentz force equation, F = q (E + v x B), is a complete description of the force on bodies arising from Magnetism and Electricity, right? So somehow it must be possible to get from the magnetism that exists in materials (like in a magnet) to this equation. I don't see how the...

Electricity and Magnetism questions...Gauss's law, grounding..etc. Alright so I am finally starting to understand the material, but I have a few questions. 1. An insulating spherical shell with an inner radius of 0.1cm and outer radius of 0.3 cm carries a total charge of 20nC. Use Gauss's law...

Homework Statement Find the net mag field at the points asked for. It is just a matter of getting the distances (r values) correct based on the points asked for relative for each wire. http://img4.imageshack.us/img4/5906/picf.th.jpg Homework Equations I think the relevant equation is: B =...

Homework Statement An electron moves at right angles to a magnetic field of .14T What is its speed if the force exerted on it is 8.7 X 10^-15 N? I am at a complete lossfor this question.

Hello, I am aware that magnetic forces can do no work. I am also aware that, in a conservative system, equations of motion that minimize the "action" (which are the true equations of motion) can be found with the euler-lagrange equation. The only information the euler-lagrange equation needs...

I need help understanding both of these terms. I know that diamagnetism is when the valence electrons of the material are paired and repel a magnetic field. Does that mean it repels like the North side of a magnet to another North side of a magnet? Or is it they don't attract at all...

Ok, I finished my physics I calculus based class, and really I don't feel like I learned a lot or mastered the material. I would spend many minutes nearing hours trying to think over my homework but with a load of other classes and the fact that we got all the hard and I do mean hard problems...

Homework Statement The question is as shown on the attachment. Homework Equations F = BIL The Attempt at a Solution To find the magnitude of the force I used the equation "F = BIL" and then I put in the values for each (B=0.25, I=15, L=0.20) and I got an answer (magnitude) of 0.75...

Homework Statement A 200-turn solenoid having a length of 25cm and a diameter of 10cm carries a current of 0.29A. Calculate the magnitude of the magnetic field B inside the solenoid. Homework Equations B = \mu0ni The Attempt at a Solution Well, I plugged the numbers into the...

Discovery challenges prevailing model! http://www.eurekalert.org/pub_releases/2008-10/nrao-ygm092908.php Astronomers have made the first direct measurement of the magnetic field in a young, distant galaxy, and the result is a big surprise. Looking at a faraway protogalaxy seen as it was...

I'm an IT person - non-scientist - but this problem has challenged me ever since high school physics: If two permanent magnets - pole to like pole - repel each other, the magnet suspended possesses potential energy. If a material can be found (that is non-magnetic and without any power...

Homework Statement Three plastic sheets that are large, parallel and uniformly charged are placed side-by-side. The electric field strength between sheets 1 and 2 is 2x105; the electric field strength between sheets 2 and 3 is 6x105. What is the ratio of the charge density on sheet 3 to that on...

What is magnetism?...preferably no links to other sites...just a conceptual answer...

Hello! Homework Statement This is a problem with magnetism and mechanical work. Two magnets are facing each other with opposite poles, where the space between them is called x. The left magnet is beeing hold still, and the right magnet moved. The space between them increases from 2 to 7...

I was just wondering; What would happen if a Halbach array of magnets were placed just beneath the heat shield on a reentry vehicle? The plasma produced by reentry is, essentially, charged particles moving at high speed. Would a Halbach array magnetically levitate the reentry vehicle away...

Homework Statement The preceding problem was an artificial model for the charging capacitor, designed to avoid complications associated with the current spreading out over the surface of the plates. For a more realistic model, imagine thin wires that connect to the centres of the plates (see...

Homework Statement Point P is midway between two long parallel straight wires that run north-south in a horizontal plane. The distance between the wires is 1 cm. Each wire carries a current of 1 A toward the north. a) find the magnitidue and direction of the magnetic field at point P...

I have a pair of scissors. The blade is about 1.5 cm wide on one end (near the handle), and it tapers down to nothing after about 7-8cm. The blades are about 3mm in thickness. It's been magnetized, meaning, I guess, I've stuck a magnet on it a few times. I'm exactly sure how or why there is...

I'm a little confused about "voltage". We learned that voltage is somewhat similar to electric field: a way to refer to the potential energy of a charge A when put near charge B without actually knowing the charge of charge A. That made sense to me, but then suddenly in class (this is college...

I was wondering if we can use magnets to spin items in a way that they will continuously spin for a very long time with good conditions of the material used. By this I mean it can spin for a very long time without being touched or relying on any other thing to help it spin. other then the pull...

Homework Statement Find the average potential over a spherical surface of radius R due to a point charge q located inside. Show that in general: (EQ 1 below), where Vcenter is the potential at the center due to all external charges and Qenc is the total enclosed charge Homework Equations...

Hello everybody: I've got a few questions that I could not find answers to, so perhaps someone on this forum can help me out: 1) If a magnet loses it's magnetism when heated, and magnetism is caused when electrons are aligned in a specific way, how come the Earth's magnetic field is...

I have few questions about magnetism: Magnetism: Is the current in permanent magnets the result of electrons orbiting the magnets atoms? Do electrons have to be in specific orbitals to create magnetism? Can the magnetism created by an electron's spin be understood through special relativity...

This is something I can't get my head around, and hopefully someone here could help. Say you have a fixed permanent magnet (not an electromagnet), and you place a metallic object with mass nearby. The object will begin to accelerate toward the magnet due to magnetic force. At the moment...

Hi, So my former knowledge of electricity and its movements made me understand that only electrons move from the negative electrode to the positive and then through the wires back into the battery. But as I am reading from my textbook (about capacitors) I am starting to feel that even protons...

Ok, I have two questions: First of all, are there any instances in which a magnet (not an electromagnet) will remain magnetized forever? I know that some magnets do lost their magnetivity Secondly, if the above is true then consider the following theoretical scenario: Imagine a large Iron...

Thunder in relation to Earth's core. Is there a relation to how the Earth's core revolves and circulates regarding thunder? What if one would track the amount of energy beeing surged and what direction it might seem to be heading, if has a direction? Is there a inderect link between lightning...

Hello, I was hoping if any of you could help me with this problem. It's one of the many I have for my homework assignment. A long straight wire carries a current i. A particle having a positive charge q and mass m kept at a distance x from the wire is projected towards it with a speed u...

A conductor suspended by two flexible wires as shown in Figure P19.18 has a mass per unit length of 0.0500 kg/m. Figure P19.18 (The picture is an attachment) What current must exist in the conductor for the tension in the supporting wires to be zero when the magnetic field is 3.70 T into...

what must change? the speed of the current or the direction of it? thanks

Hi I read in some book that current creates magnetism. but what current? DC or AC currents? steady or changing currents? transformers works with ac currents and not with dc. this is confusing me... Thanks

I understand that magnetic force is a relativistic effect of electric force. Is there a force which is the relativistic effect of gravitational force? If a stationary observer sees 2 electrically charged particles moving parallel to each other at the same very high speed relative to himself...