Currents Definition and 476 Threads

Homework Statement The Attempt at a Solution As at t=0 the capacitor behaves as a wire ... so the circuit at t=0 will be like: q at any time for this circuit will be, q \ = \ CE(1-e^{-t/\tau}) + Q_oe^{-t/\tau} differentiating it will give current, i \ = \ \frac{Ee^{-t/\tau}}{R} \ - \...

How do I find the direction of these things? The right hand rule only works when I have the current and it's asking for clockwise/counter-clockwise, and the left hand rule only works when I have two of the three: Current, Magnetic Field, and Force. Example...

1) Using Kirchoff's Laws, find all the currents flowing in the cct. 2) Hence, determine the voltages across all resistors and check that each loop complies with KVL

hello, this is a pdf from a book:-- https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_XrsbDdR9NEOGQzZTEzMmMtMDdhNS00OTJkLTljZmItY2UyYzFjZTllMzM0&hl=en&authkey=CNeg85sN in fig 5.13 12v supply and 8v supply are connected to each other. perhaps the ground symbol tells us...

1) Using Ohm's Law determine the eqv resistance across the battery. 2) Determine the currents through all resistors

Hey guys, the other day i was reading about eddy currents and it was getting intersting, except i had a few questions going through my mind that i couldn't find answers to and wanted to ask: say we have a circular bit of aluminium which is our brake disc and an electromagnet which induces the...

Homework Statement Two identical long bulbs are wired in series and connected to a 4.5-volt battery pack. The resistance of each bulb is 50 ohms. a. Determine the voltage across each bulb. b. Determine current through each bulb. c. How does this compare to the current flowing out of...

Homework Statement Find the currents [PLAIN]http://img695.imageshack.us/img695/7042/78217840.png Homework Equations Using Kirchhoff's Law, Loop, Junction ruleThe Attempt at a Solution The problem here is the inside circuit .I try to solve it as one emf, one resistance, but honestly I do not...

Homework Statement Calculate the currents in each resistor in this figure: http://session.masteringphysics.com/problemAsset/1084690/2/GIANCOLI.ch26.p32.jpg Homework Equations Kirchhoff's rules In a closed loop: the sum of voltage is 0 A a junction: the sum of current is 0 The...

Homework Statement Find terminal voltage, currents of each battery [PLAIN]http://img26.imageshack.us/img26/8667/questionl.jpg Homework Equations \epsilon=I(R + ri) Vterminal= \epsilon \pm I*ri The Attempt at a Solution Find current: I=\frac{\epsilon1+\epsilon2+\epsilon3}{R+r1+r2+r3} Fine...

Homework Statement The question is just asking to find the current through each of the resistors. Our teacher taught us this loop current method, and then we have to use a matrix to solve for the currents. i1 denotes loop 1 and current, etc. Homework Equations Loop 1: 4i1 - 2i2...

Homework Statement A 4.0-µF and an 7.0-µF capacitor are connected in parallel across a 25-V battery. Find the total charge stored on the two capacitors. Homework Equations q=Cv The Attempt at a Solution i did the eqivalent capactiy*25 volts to get 275 C as the charge but that...

I'm not sure I understand the point of alternating currents. From what I understand, it's electrons spinning in circles. So, is alternating currents essentially the way we store electrons? That way we keep them spinning around themselves?

i know i haven't understood the concept of eddy current and that is why i am posting this question: why are EDDY currents CIRCULAR (why form a loop in circular form)? please also explain this answer that statement that i found on : http://wiki.answers.com/Q/What_is_an_eddy_current "When...

i know i haven't understood the concept of eddy current and that is why i am posting this question: why are EDDY CURRENTS circular?

I understand that using F = qv x B and the fact that positive currents generate counter clockwise magnetic fields, it can be concluded that two parallel wires carrying currents in the same direction attract. But what about when you think about it in the frame of reference of the charges in...

Given the Dirac equation and its conjugate, how do I show that j^\mu = \bar{\psi} \gamma^\mu \psi is a Noether current? Is there even a standard formula for Noether currents or does it vary depending on each individual case? And if it does vary, how do I go about figuring how to apply it to...

Homework Statement Use Kirchhoff's rules to find the currents I1, I2 and I3 shown in the circuit below: [PLAIN]http://img811.imageshack.us/img811/3640/13608736.gif The Attempt at a Solution Kirchhoff's junction law gives: I1+I2-I3=0 I have calculated the voltage rise/drop in the...

Homework Statement Hello i just have an interesting question, and was wondering if my answer to it had any validity. Ok so i did an experiment The Current balance experiment(for everyone not familiar with it, you can google it and get all the info you want) to try and estimate mu naught...

Homework Statement For the circuit in the figure, determine i1to i5 http://i55.tinypic.com/dokoc5.png Homework Equations current division: in = (Requivalence / Rn) * itotal Requivalence in parallel = R1*R2 / R1+R2 The Attempt at a Solution || (parallel), and +s (series) 1ohms ||...

It is usually said that gravitation is the dominant "force" on large scale, because Universe is electrically neutral on large scale. But what about currents? Maybe effects of currents are disappearing statistically, but I think that this is not trivial. What is the truth?

Homework Statement I have a closed circuit, with 7 bulbs, all of unequal resistances. I know three currents, 300, 200 and 500. I have 4 unknown currents, those fllowing through A, b, C and D which I need to find. There is a graphic for this which I don't know how to insert, but the...

Hello, Those days I wonder if the magnetic field from the Sun, could make the Eddy's currents inside the core (ferromagnetic) of our planet, because of the rotation of the Earth. (like a induction cooker) It would result a magnetic field on the Heart, and if the magnetic field from the Sun...

It is known that on a wire carrying steady current there are surface charges (and hence electric field outside the wire, but let's forget about it). This surface charges play an important role to maintain a uniform electric filed along the whole wire. There are only few geometries for which one...

Homework Statement Why is the force of a wire to another wire that is perpendicular to it zero? Homework Equations biot-savart law The Attempt at a Solution

Hey guy, Ive been recently investigating the phenomena of eddy currents, particularly that of a magnet falling down a copper tube. To the people who haven't seen it before, basically the magnet reaches terminal velocity in the copper tube extremely quickly, and takes a long time to leave the...

Homework Statement The currents in a DC circuit is to be calculated, and I end up with a system of 5 equations and 5 unknowns. This is where my headache starts. Homework Equations (1) I_{1}=I_{2} + I_{3} (2) I_{2}=I_{4} + I_{5} (3) 6 - 2I_{1} - I_{3} = 0 (4) 4.5 - 5I_{2} - 3I_{5} +...

Having some generic curved spacetime, what are the Noether currents that are guaranteed to exist by diffeomorphism invariance? Is the energy-momentum tensor such a current?

Hi,I am new here^^17 years old... I got a little problem with understanding how simple alternating currents motors/AC Motors work... Anyone has a good Table or Figure?? Magnetic problems: 1)Whats the difference between inducing current and normal electric current?? 2)Whats the meaning...

Hello all! I must design an ac ammeter which uses successive approximation ADC,has a specified voltage of 0,15V and individual entrance resistors for measuring currents of 200mA,500mA,1A. Any suggestions on how to build such a device would be highly appreciated!

Currents! Homework Statement Why can't the potential difference in household currents be changed? Homework Equations Conceptual. The Attempt at a Solution Is it just because the fuse will ignite if overheated?

1. Homework Statement I just have a question concerning an unbalanced coaxial cable. By unbalanced, I mean that the inner and outer currents are not equal magnitudes of the opposite direction of each other. My homework problem has an inner current of +100[mA] and an outer current of 90[mA] in...

today i was introduced to AC currents in my electricty/magnetism class. Perhaps we're not to this point yet, but I'm not sure what's the use of an alternating current, compared to DC currents. dc currents can only go in one direction, but what's the practical use for alternating one? sorry...

Homework Statement please see attached picture. Homework Equations The Attempt at a Solution

I have read that locomotives use eddy current braking systems, and one article mentioned that this system has also been used to charge batteries in a recovery circuit. However, I can not find details on this idea. From what I understand, the train has conducting discs attached to the wheels, and...

My question: Should the sum of all bound currents always be zero? For example, should the bound currents of a cylinder with both bound volume current density and bound surface current density always sum up to zero? Does the uniformity of current ran through the cylinder have any effect...

Suppose we are looking at the cross-section of a cylindrical current-carrying wire. Due to the motion of the electrons in the wire, it can be said that at all points at the surface of the wire a magnetic field tangential to the wire exists. Since there are electrons moving in that region as...

Suppose we have a current-carrying wire and an electric charge which is moving parallel to the wire with the same speed and direction as the electrons in the wire. The wire produces a magnetic field which acts upon the charge through a force. From the charge's reference frame, though, no...

Homework Statement In the figure 29-49, four long straight wires are perpendicular to the page, and their cross sections form a square of edge length a = 20 cm. The currents are out of the page in wires 1 and 4 and into the page in wires 2 and 3, and each wire carries 19 A. What is the...

I don't really understand what is eddy current. Is it just the current that is formed using Lenz's law? Or is it different? My idea of eddy current is that it is of many small swirls all over a metal plate that opposes the force exerted to move the plate. Thank you.

I understand pretty much everything related to this, except how many currents should I put when arbitrarly putting them. The number of resistors? The number of wires? The number of loops? I'm seriously lost here, thanks!

How do you find unknown one emf's and unknown currents in a circuit with known resisters and two known emfs?

I am doing some work with electric circuits and just have a general question. With the concern of a given current in three branches of a circuit, is the total current the sum of the current through the resistors? Are they all equal, or does half of the current flow through each resistor? I think...

Homework Statement If you put a POSITIVE test charge in an electric field, does it move toward a higher or lower potential? If you put a NEGATIVE test charge in an electric field, does it move toward a higher or lower potential? Homework Equations The Attempt at a Solution...

Referring to the bridge circuit of fig P90, if I=6A, I2=4A, and I3 = 0, find I1, I4, and I5. I did, I1=2A I4=4A I5=2A My logic being, since I is 6A, and I2 is 4A, I1 must be the difference, 2A. since I4 is coming from I2 and I3 it should be the sum, (0 + 4A = 4A). and I thought because I5 is...

the title says it all... my question is simple... are there transistors easily available that can be configured to provide upto 3ampers in the saturation region? if yes, whch ones?

Homework Statement It is given that when a copper or aluminium bar is set in oscillation in a magnetic field eddy currents are produced inside the bar. Should it be necessary that the bar should be made of a non-magnetic substance such as copper, aluminium etc.? Can it be a ferromagnetic...

I know that when you cut magnetic field lines with a wire you get an electric current. I know that if the left side of your screen was a magnet with its south side facing the north side of an other magnet which is the right side of your screen, and a wire coming in from the top of your...

There are two AC current carrying conductors.(both are of the same frequency) How do you compare the currents to know if they're not equal at all times...? Please Answer as soon as possible ...

A solid metallic body moves closer to a magnet. This causes increase in magnetic flux linked with the body. Eddy currents are generated in it. Now, the problem is: will the body come back to its original position or will stay there? I say that eddy currents will generate heat which will go...