Currents Definition and 497 Threads

Hello everyone! I have been searching all over the internet for an answer to this question: will moving a magnet within a coiled wire induce a current even if the magnet "stays" within the coiled wire for a matter of seconds? I am planning an improvement to an experiment where a magnet...

Homework Statement A fat wire, radius a, carries a constant current I, uniformly distributed over its cross section. A narrow gap in the wire, of width w << a, forms a parallel-plate capacitor, as shown in the figure above. Find the magnetic field in the gap, at a distance s < a from the...

I've been playing around with the QCD Lagrangian to get a better understanding of how it works. I can derive some classical, Maxwell-like equations; the inhomogenous ones are \nabla \cdot \vec E^a = -gf^{a}_{bc} \vec A^b \cdot \vec E^c + \rho^a \nabla \times \vec B^a -...

Consider this quote from Mandl and Shaw, p. 237 ...this interaction coulpes the field W_{\alpha}(x) to the leptonic vector current. Hence it must be a vector field, and the W particles are vector bosons with spin 1. Could someone explain this for me? I do not understand the "hence"...

Not a homework question, Just trying to get more information about it. Its hard to find a textbook or a site that explains this well. thanks

i've just had this thing running through my head that I'm trying to resolve: 1. two parallel wires that conduct a current (same charge carriers) will attract one another, that is the magnetic force each wire emits due to the flowing current will induce an attractive force in the other (charge...

HF HV to LF? I wanted to say that I have searched the site and it is very imformative, glad to be apart of it. That being said I had a question, what means would you use to convert high frequency currents to that of line current(60hz)?? I have searched and searched on google and have not...

Homework Statement A long current-carrying wire, oriented North-South, lies on a table (it is connected to batteries which are not shown). A compass lies on top of the wire, with the compass needle about 3 mm above the wire. With the current running, the compass deflects 10 degrees to the...

Homework Statement For the three (simple?) circuits, I'm asked to solve for the voltages at A and B, and also the current I. For figure 1, I assume that is just a simple voltage divider, with the voltage at A to be 5*(1/21) correct? I'm a little more confused with the circuit in figure...

Homework Statement From serway's book chapter 23(electric fields), questions section. Homework Equations --- The Attempt at a Solution The obvious answer would be that it is safe because the student holding the sphere is insulated from the ground, but what does that really mean ? If I try to...

Homework Statement Two negative charges repel each other. Two parallel wires with current going in the same direction attract each other. Yet if one walks with the moving charge in the wires, the charges appear stationary and should repel each other - explain why if you are stationary...

Homework Statement An uncharged 1.15 uF capacitor is in series, through a switch, with a 4.50-M Ohms resistor and a 24.0- V battery (with negligible internal resistance.) The switch is closed at t = 0 and a current of Ii immediately appears. (Which I calculated to be 5.33 uA.) How long will...

Hi All! I am working on the Eddy Currents problem. I was to set up the problem and derive some equations for the pivot pendulum with Eddy currents. Please see attachment. As you see the pendulum swings between max point ( just outside the B field) and enters the B field and then...

Hey all, I was wondering about a varied version of something. I know that if you run a magnet up and down a tightly coiled tube of copper, it creates an electric current through the wire. I also know the reverse, which is that if you passed a current through that wire, while it was wrapped...

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

I am not asking if they are considered as input into the armature's magnetic field. I strongly believe they are NOT even considered when designing motors. The question is, "DO THEY EXIST IN MOTORS?" Based on evidence from conventional theory, it appears they do infact affect the output of...

Attached is a picture of the object that I am trying to figure out the forces due to currents that will be acted on it. Here are the questions I have ( I really just need some direction in the area of appropriate formulas) 1) what are the force againts the surface of the collector in foot...

Homework Statement What observation of the process: (anti muon neutrino) + (electron) -> (anti muon neutrino) + (electron) constitutes unambiguous evidence for weak neutral currents, whereas the observation of (anti electron neutrino) + (electron) -> (anti electron neutrino) +...

From EurekAlert, 16 April. Mysterious striped currents in our oceans IT’S amazing that nobody has spotted it before. Superimposed on every ocean on the planet there is a striped pattern of currents. Yet what causes them is a mystery. Between 1992 and 2003, Peter Niiler of the Scripps...

1. Is it induce e.m.f is a force? 2. What is the eddy current?

Its been 15+ years since I have done any calcs like this and am very rusty, so even just a pointer in the right direction would be really appreciated... I need to calculate/estimate the magnitude/value (IF any!) of eddy currents that would/could be generated in an ultra high speed rotating...

Homework Statement I have to find the current through each resistor in this: http://i7.photobucket.com/albums/y297/SpaceTrekkie/Physics/Untitled.jpg circuit. All the resistors labeled R1 are 100ohms, the one labeled R2 is 1000 ohms and E1 = 10V E2= 6 The Attempt at a Solution I...

There is something on Lenz's law about induced current and the magnetic field that I don't quite understand. "Apply Lenz's law that when the magnet is brought near the coil, the magnet's magnetic field through the coil increases, and therefore the flux increases." Here, why the magnet's...

Homework Statement \epsilonbatt = 12V Find the following currents. The current I1 through the resistor of resistance R1 = 15.0 ohms. The current I2 through the resistor of resistance R2 = 45.0 ohms. The current I3 through the resistor of resistance R3 = 25.0 ohms. The current I4 through the...

Hey everyone, I'm having trouble with b and c and any help would be appreciated! I attached two pictures on the bottom (one of the entire problem and one of just the diagram) Homework Statement Five loops are formed of copper wire of the same gauge (cross-sectional area). Loops 1-4 are...

i'm a bit confused about the currents in the expression for a matrix element for an interaction... e.g. you could have a current like (adjoint spinor)x(spinor) which is scalar, this makes sense to me. or you could have a current like (adjoint spinor)x(gamma matrix)x(spinor) which is vector...

[Solved?] Simple question about amping electical currents Homework Statement I am attempting to build a pocket guitar amplifier. So far this is what I have. http://img174.imageshack.us/img174/6724/dscf0004yf2.th.jpg What you can see in that picture WORKS! The tiny electrical current from...

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 An electromagnetic "eddy current" brake consists of a disc of conductivity \sigma and thickness d rotating about an axis passing through its center and normal to the surface of the disc. A uniform B is applied perpendicular to the plane of the disc over a small area a^2...

Hi, I'm currently studying in an introductory semiconductor course where we use the following equations (numbers 1-5 on the first page): http://web.mit.edu/kimt/www/6.012/TheFiveEquations.pdf as a model of the underlying physics. Now, it is claimed that at thermal equilibrium, we can take J_e...

Homework Statement The 10.00V battery in the figure is removed from the circuit and reinserted with the opposite polarity, so that its positive terminal is now next to point a. The rest of the circuit is shown in the figure. Find a, the current in each branch and b, the potential difference...

Homework Statement More of a general question: I have a situation where I have a conductor at eight volts and a conductor with zero volts. Just because there is an electric field, does that mean there is an electric current present in the system? And what is the direction? Homework...

1. There is a current of 0.25 A in the circuit of the figure What is the value of the resistance R? Hockay so. I know the change of voltage throughout the loop is 0. therefore 0 = E1 - I(R1+R2) - E2 - 1R(unknown) 0 = 6V - 0.25A*18ohm - 12V - 0.25A*R through algebra i get R=42. And...

I am trying to find the currents I_D1 and I_D2 labeled in the picture by the arrows. I am stumped on how to obtain the correct values for the currents. I am having trouble using either KCL or KVL. This circuit seems simple but has me stumped...

Hello everyone. I am trying to measure the position of a magnet moving inside a steel tube using a magnetic sensor on the outside. Eddy currents are causing errors due to phase shifts and amplitude changes. Any ideas? Can eddy currents be re-directed using selective copper paths? Since eddy...

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?

Hello everyone, first post on this forum... Recently I've been trying to understand how ocean currents work from a general perspective. While studying, an intrigueing question popped up in my mind, and I haven't been able to let it go unanswered. It is simply: If the Earth was a...

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...

Homework Statement Solve for all of the currents using superposition. Homework Equations Remove the one source and solve the problem in two steps. The Attempt at a Solution Ive isolated each source separately but once i get to that point I am completely stumped on what route to take. I know...

Homework Statement what is the frequecy F for the alterating current U(T)=15cos(314t) A Homework Equations Am really new at this kind of problem but i think 314 is how many times the current rotates or fluxuates in 1 period so the F has to be the distance between waves? The...

Why is the chromoshphere millions of degrees hotter than the surface of the sun? in a body that the heat should radiate from the centre isn't this highly unexpected? i have been looking into this and the only good explanation in a science journal is this one from Harvard Astrophysical Journal...

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...

Homework Statement The voltmeter in the circuit sketched in the link below reads 100 volts. What currents would ammeters indicate for I1, I2, and I3? What is the phase relation between the applied voltage and I3? http://i43.photobucket.com/albums/e394/risendemonx/prob3pic.jpg...

Homework Statement A compass needle points 20 degrees E of N outdoors. However, when it is placed 8.0 cm to the east of a vertical wire inside a building, it points 55 degrees E of N. What is the magnitude and direction of the current in the wire? The Earth's field there is 0.50 x 10^ -4 T and...

Homework Statement Two narrow beams of electrons with velocities v and -v are injected into an evacuated chamber along the length l. Each beam moves with constant speed and carries a current I. The tendency for the beams to deflect each other through their mutual interaction is compensated...

Homework Statement An inductor is connected to a 15 kHz oscillator. The peak current is 65 mA when the rms voltage is 6.0 V. What is the value of the inductance L? In mH Homework Equations Il=Vl/Xl Xl=frequency*L The Attempt at a Solution Well I thought this problem was really...

Homework Statement Homework Equations I suppose the energy density equation applies here: (P2-P1) + pg(y2-y1) + 1/2p(v2^2 - v1^2) = Epump/vol - IR and I = Av The Attempt at a Solution My initial thought was that the current is the same. But then, since current is Av...

Homework Statement Two very long straight wires carry currents perpendicular to the page. Wire 1, which carries a current I1 into the page, passes through the x-axis at x=+a. Wire 2, located at x=-2a, carries an unknown current. The net field at the origin (x=0), due to the current-carrying...