Currents Definition and 476 Threads

Homework Statement Two parallel wires have currents passed through them which are in the same direction. Draw a diagram showing the directions of the currents and of the forces on the wires. Alternating currents are now passed through the wires. Explain what forces would act if the currents...

Why must steady currents be non-divergent in magnetostatics? Based on an article by Kirk T. McDonald (http://www.physics.princeton.edu/~mcdonald/examples/current.pdf), it appears that the answer is that by extrapolating the linear time dependence of the charge density from a constant divergence...

Homework Statement Find the value of the RMS current in the following cases: (a) a sinusoidally varying current with a peak value of 4.0 A, (b) a square wave current which has a constant value of 4.0 A for the first 3 ms and -2.4 A for the next 2 ms of each 5 ms cycle, (c) an alternating...

Hi. Assume a long hollow wire that both carries a nonzero net charge and a current. Is it still true that all charge sits on the outer surface of the cable and that the empty space inside is field-free (Faraday cage)? I know proofs of those facts in electrostatics using Gauss' theorem, but they...

Dear PF members. I have trouble understanding how zero sequence currents circulate in a delta winding. For example zero sequence currents such as 3rd harmonics, they will circulate in the delta winding and get trapped, why? Why can they not go further? I have recently started to study...

1. The problem statement, all variables and given/known data Homework Equations I3 + I1= I2The Attempt at a Solution [/B]

Hello there, I've just been learning about surface magnetization currents circulating around hypothetical square loops. Since the magnetization is uniform the circulation currents cancel where the square loops are adjacent to one another and it can therefore be said that the current circulates...

Since the field in the title is opposing the original magnetic flux that causes the induction, how can it be reduced? I understand that a laminated magnetic core can be used. 1) Where is this magnetic laminated core placed? 2) Can it be obtained from specialized manufacturers? 3) My choice for...

Hi, I've been trying to figure several simple things about electric and magnetic fields, their relationship with current. If you could please help me understanding this, it would be really helpful. From what I've read these were presented as natural laws: 1. Changing magnetic field induces...

Homework Statement I added a circuit that I drew in microsoft paint to add a visual. Sorry for its ugliness! ;D Homework Equations V = I*Z Ieff = I / sqrt(2) Qreactive = V^2 / Z Pavg = (power factor) * (Veff) * (Ieff) Sapparent = ((Ieff)*(Veff))/2 The Attempt at a Solution Since this is...

Hello, I have a silicon wafer with a 50nm layer of copper sputtered on it. I coated it with a 1µm of positive photo resist and patterned it with a UV laser stepper. Then I developed it and washed it thoroughly. The pattern has a surface area which measures appx 1300µm x 8µm. What I want to do...

i tried to fig it out by watching a lot of vid on it but no chance help me

In a 3-phase induction motor, rotor current demagnetizes the air gap and hence, stator draws more current (to keep the flux constant), which is the reflection of rotor current. This is like a rotating transformer which consumes active power. An induction generator on the other hand, supplies...

Suppose a 3-phase IM is operating on a 50Hz power supply. When the motor is loaded, more current is drawn from the stator because of the demagnetizing effect of the rotor current. But the rotor current has a lower frequency i.e. slip*stator frequency. Still the reflected current in the stator is...

We recently performed one experiment regarding measurement of negative sequence impedance of an alternator(unloaded) in our lab session. The alternator was star connected and we shorted Y and B phases together, leaving R phase open(an L-L fault). How does this arrangement generate negative...

1. A current in a wire which has a length of 2.00m in a magnetic Field of 0.030 Teslas, feels a magnetic force of 0.810 Newtons. What is the current in the wire?2. F=IlB, Find I3. F= 0.810, l= 2.00m, B= 0.030 T, I=? (A) I= l x B I= 2.00m x 0.030 T I= 0.074 A F...

Homework Statement Homework Equations KVL: At any instant in a closed loop the algebraic sum of the e.m.f's acting round the loop is equal to the algebraic sum of the p.d's round the loop. The Attempt at a Solution 3.1 R1 = BROWN, RED, BLACK, NONE R2 = BROWN, GREY, BROWN, SILVER R3 =...

My syllabus has point *' 'describe and compare the forces on mass, charge and current in gravitational, electric and magnetic fields, as appropriate" what does this mean ?

Homework Statement Find I1, I2, I3 as well as the voltages across each resistor. R1= 50 ohms R2= 220 ohms R3= 150 ohms Homework Equations Kirchhoff's loop law Kirchhoff's junction lawThe Attempt at a Solution Loop 1: Starting from the negative terminal of the 10V battery (ccw) 10V - 50...

I've got a rather simple inquiry, but I haven't been able to get a straight answer via Google searches. When evaluating the impedance of an inductor, do eddy currents represent a series resistance through, or a parallel resistance around the ideal inductor? I've read that eddy currents are...

Homework Statement Homework Equations i1+i2-i3=0 50i1+75i3=1 100i2-75i3=1 The Attempt at a Solution matrix A=1 1 -1 0 100 -75[/B] 50 0 75 matrix B= 0 1 1 i1= -6ma i2= 23ma i3= 17ma My instructor gets i1= 6ma...

If my understanding is correct, with respect to dry-type building power transformers, due to the virtues of the transformer as a dumb machine it really doesn't care which side of itself is the primary versus the secondary. In other words a 480D-208Y tranformer can be correctly connected such...

Homework Statement Two alternating currents i1 and i2 flow into a circuit node,the output current i is given by i1 + i2. Calculate the amplitude of i and the first time it occurs. i1=5sin(50t +Pi/3) i2=6cos50t Homework Equations The Attempt at a Solution 5 sin ( 50t +60˚) = 5 ( sin...

Homework Statement [/B] Use the following values: E = 12.0 V , R1 = 35.0 Ω , R2 = 22.0 Ω , R3 = 41.0 Ω , and R4 = 14.0 Ω . Find the following currents: the current I1 through the resistor of resistance R1 = 35.0 Ω the current I2 through the resistor of resistance R2 = 22.0 Ω the current I3...

Homework Statement A combination circuit powered by a 6.0 V battery is shown. What is the total current through this circuit? I don't know how to determine where the signs go, for example if the right side of a resistor is positive or the left side is positive Homework Equations What is the...

Hi pf, Could someone please explain to me why the back emf on the primary caused by eddy currents does not result in power loss. From what I have been reading about transformers eddy currents have two effects: 1) Producing heat (P=I^2R) 2) Producing a flux which opposes the primary flux I am...

Can a moving magnetic field create eddy currents in a conductor ? Moving a magnet in and out of a solenoid makes a current flow in the solenoid. I know that a changing magnetic field induces emf in a conductor but what about a moving magnetic field ? Are eddy currents present in the solenoid...

If a magnet is being moved in a conducting coil, are eddy currents produced in that coil ? And why ? I think the answer is yes bcz a changing magnetic field creates eddy currents in a conductor (whether it was a coil or not) . Correct me if i am wrong . Thanks !

So assuming I1 = 1<10 and I2 = 2<20 And assume these current sources are in parallel, pointing in same direction. Can I say total current is I1 + I2 = 1<10 + 2<20 ? I would convert the phasor to complex number to combine them, but will this work?

Homework Statement Find the current passing through the 5mH inductor in steady state. Homework Equations I=V/R The Attempt at a Solution Since it says steady current, so no change in current which implies that the inductors act as conductors so the current should just split equally So I...

Hello all, This might sound very optimistic for a project but I want to design a thermonuclear fusion reactor. Does anyone know how I can calculate the required plasma current I need in order to start a thermonuclear fusion process? I am using a mixture of Deuterium-Tritium gas. Thanks!

I had the idea of making an hourglass timepiece employing lenz's law using a magnet and copper tube (or copper bars for visibility). Any idea how accurate my hourglass will be? I know Lenz's law is effected by temperature (not sure by how much). If I drop a small magnet drop through a small...

Homework Statement I'm having a bit of trouble evaluating the following commutator $$ \left[T^{+},T^{-}\right] $$ where T^{+}=\int_{M}d^{3}x\:\bar{\nu}_{L}\gamma^{0}e_{L}=\int_{M}d^{3}x\:\nu_{L}^{\dagger}e_{L} and...

Hello, 1. Homework Statement Suppose we have the following Lagrangian density, in ## 3 + 1## dimensions: $$L = \frac{1}{2}\partial_{\mu}\phi \partial^{\mu}\phi - g \phi^4$$ Under the dilatation (scaling transformation): ##x \rightarrow \lambda x^{\mu}, \phi (x) \rightarrow \lambda^{-1}...

I've been googling around, and I can't seem to find a straight answer to this: Do eddy currents generated within an inductor core change the inductance, the impedance, or both? My reason for asking is to understand whether more or less eddy currents will change the resonant peak of the...

Hi All, I am new to this forum. Thanks for viewing my question in advance. I have a confusion about the duration of eddy current. All the formulae I found are to calculate the intensity of the current. I am implementing a switch in my experiment which will turn on/off the magnetic field inside...

Homework Statement An electric fan which is plugged into a 115 V(rms), 60 Hz socket in your house can be considered as made up of a 1500 Ω resistor in series with a 1.4 H inductance. How much power is dissipated by this electric fan on the average? (in W) Homework Equations P = IV = I^2 R I =...

Hello. If we assume an ideal transformer, why do we use a.c current in a transformer? I've searched and answers are that we need a changing electric current to produce a change in magnetic flux, using Ampere's law. However, Faraday's law states that a voltage produced a changing magnetic flux...

The problem I want to calculate ## |I_1| ## The attempt ## V_m = Z_{total}I_1 \\ I_1 = \frac{V_m}{Z_{total}} ## ## Z_{total} = \frac{ \frac{1}{jwC }\cdot (R + jwL) }{\frac{1}{jwC} + R + jwL} \\ \frac{ R + jwL }{1 + jwCR + jwCjwL} \\ \frac{ R + jwL }{1 - w^2LC + jwCR } \\ ## ## I_1 =...

Homework Statement [/B] A cubic block of uniform linear magnetic material is placed in an otherwise uniform magnetic field Bo = Bo*zˆ. The block lies such that z^ is a normal of the top face. a)Compute the new H field everywhere. b)compute the new B field everywhere Homework Equations & The...

Homework Statement This is quite an easy problem but I'm not sure if I set up my equations correctly, and I want confirmation. We are given the following circuit: And our task is to determine the loop currents i_{1}, i_{2}, i_{3}, i_{4} . Homework Equations Kirchhoff's first law: sum of...

Homework Statement Show that the conduction and displacement currents cancel each other for a spherical radioactive solid emitting charged particles radially outwards Homework Equations Maxwell's equations Current density (j) Displacement current density (jd) The Attempt at a Solution I...

Homework Statement Find currents through M and N Homework Equations Current out must be current in. The Attempt at a Solution I think that it is simply 3 parallels running with 5A of current. So, M is in series with the 2A current thus also has 2A of current. Would N also be in series with...

Hello Forum, A coaxial cable is a two conductor transmission line. If we connect a DC voltage source via a coaxial cable to a resistor so that the positive terminal is connected to the inner conductor and the negative terminal to the shield , the current will flow through the whole...

When deriving the conserved currents from continuous symmetries, my book states that we can also add a 4-divergence to the lagrangian density which does not change the action under variation. The four divergence can be transformed into a boundary integral by stokes theorem. However, my book...

I have read articles regarding Chinese junks which utilise rudders made of rubber, and they usually have diamond shaped holes in them. These articles claim that the holes provide better handling of the junks compared to a full rudder without holes in them. What are your thoughts regarding how...

Im a bit confused about one point. Can Eddy current, and induced current exist at the same time...? If a conductor is a part of a closed circuit, and there is a change in magnetic flux over time, both Eddy current and induced current would oppose that change? Let's assume a conductor that is a...

The book I am working through is beginning to dive into induced currents and Lenz's Law. When a conductor is moving perpendicular to a magnetic field, the charge carriers inside will experience a magnetic force; This causes the charges to move. Eventually, the electric field from the charge...

Homework Statement A 10 ohms resistor, a 12 microFarad capacitor and a 28 mH inductor are connected in series with a 170 V generator. A.) At what frequency is the rms current maximum? B.) What is the maximum value of the rms current? Homework Equations A.) Fo = 1 / 2pi sqrtLC b.) Irms = Vrms...

Hi, I would appreciate some help with this issue: I want to calculate the probability denstities and currents from the Schrödinger and Klein-Gordon equations, and I've found 2 ways so far, the one that gives the "standard" result (the one I've seen on my course, or wikipedia) but I don't...