Currents Definition and 476 Threads

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 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...

Homework Statement A circular loop of wire and a long, straight wire carry currents of I1 and I2 (see the drawing), where I2 = 5.2I1. The loop and the straight wire lie in the same plane. The net magnetic field at the center of the loop is zero. Find the distance H, expressing your answer in...

someone knows how eddy currents in transformers are produced? by friction , resistance or heat transfer? i mean the classical example is the wheel that is braked between the poles of an electromagnet, but how this applies to a transformer where there is exactly the opossed, a fixed conductor...

Question: 1. a) what is the force per meter on a wire carrying a 9.80-A current when perpendicular to a 0.80-T magnetic field? b) What if the angle between the wire and the field is 45°? For part a) I know that F = ILB, where I is the current, L is the length of the wire and B is the size of...

A circular loop of wire and a long, straight wire carry currents of I1 and I2 (see the drawing), where I2 = 4.9I1. The loop and the straight wire lie in the same plane. The net magnetic field at the center of the loop is zero. Find the distance H, expressing your answer in terms of R, the radius...

Please help me if you can... question: Use the following quantities to calculate the magnetic field strength of the horseshoe magnet. Mass of coil: 20 grams current in coil: 2.0 amps length of bottom of coil: 10cm angle coil makes with vertical: 30 degrees Hint: Equate magnetic...

Something I keep on wondering about - wouldn't currents have some inertia, some tendency to keep on moving, even if there is no inductance? After all, electrons have inertia and they would tend to keep on moving in the same direction even when there's no electric field pushing them ... Is...

A 23 V battery is connected to terminals A and B below. (a) If R = 95 Ω, find the current in each resistor (/12, /55, /95). (b) Suppose the value of R is increased. For the 12 Ω resistor, does the current flowing through it increase or decrease? What about the 55 Ω resistor? What about...

http://img335.imageshack.us/img335/8383/physics4a8ua.th.png http://img335.imageshack.us/img335/8000/physics4b6vo.th.png "Find the currents in the circuit branches in [the first figure on the left above]." V1 = 20V, V2 = 10V, R1 = 5.0 ohms, R2 = 4.0 ohms, R3 = 6.0 ohms, R4=R5=R6= 2.0 ohms...

9 - 2.7(I) - .038(I) = 0 13 - .023(I) + 2.7(I) - 9 = 0 I don't know how the dead battery effects it and how to figure out the different currents thru the different resistors

I'm having trouble with curcuits, my first problem is that I'm not sure if this is a combination parallel-series curcuit? For the simple circuit (attached diagram) determine the current through each resistor and the potential difference at the 5 ohm resistor. I think that the 2 ohm...

Another Electromagnetics question... Two long wires carry equal, but oppositely directed, 25 A currents. What is the magnitude of magnetic field due to these currents at point P? The wires are 0.1 m apart and point P is 0.05m in between the wires. Would the following be the correct way to...

Gents, Is it possible to have the not singular chiral current (singularity is due to the product of fermionic operators) and at the same time the translational invariance. Normaly to get rid of singularity in chiral current one is useing the point splitting regularisation (little shift of...

I came across the following problem recently: http://www.tubaroo.com/stuff/circuit.gif R_1 = R_2 = 4700 \Omega C = 0.060 F V = 12 VS1 has been closed for a long time. At t = 0, S2 is closed. Sketch a graph of the currents I_1 through R_1 and I_2 through R_2. I wasn't really sure where to...

HELP ME PLEASE! Given B=0.80 T, a square coil with a single loop with length of each side of 20 cm, a current of 5.0 A where there is an external constant uniform magnetic field, what are the size and the direction of the magnetic force on just the lower section of the loop due to the 0.80 T...

Hi all, I only have a real basic knowledge of quantum mechanics and I am finding a paper that I am taking quite challenging. If it is possible for someone to give me a hint or starting point on this folowing problem that would be great. For problem - see attachment Thanks.

I have to list the temperature (cold or warm, the black ones "are the same temperature as the current leading into it") of the following currents: North Atlantic Labrador (Newfoundland) Oyashio (Japan) Alaska California Gulf Stream Canary (NWAfrica) Kuroshio (Taiwan) Peru...

Dear Gents, I have one question: Can I say that if I I have some currents, charges form these currents (integrals over time components) and these charges form a close algebra of some group SU (N), then I say that the particles sitting in these currents (all possible incoming/outgoing...

Help - Loops Currents. :( hey there I'm revising for an exam and i can't really do loop currents i was trying to do this sum http://mathonweb.com/help/backgd4.htm (example2) but kept getting the rong sign for equations (for shared resistors):( could someone please explain to me! thanx in...

This problem doens't seem hard, but I am rusty on the right hand rule... Four electric currents, equal in magnitude are arranged at the corners of a square as shown in the figure. http://img368.imageshack.us/img368/2654/fourcurrents7jc.jpg Two currents go into the page (marked by x), and two...

I have been taught that the voltage in a capacitor and the current in an inductor cannot change instanteously. This is important especially when solving differential equations for a circuit network. Can someone explain to me why these events cannot happen? To the extent of my knowledge for these...

Hello, I've just entered this forum and... the world of Physics. And I already have tremendous enigmas. Let's start with this. Oersted revealed that a static magnetic field exists in the nearby of a current loop. Now "current" means "moving electric charges" and e.m. theory states that a moving...