Currents Definition and 497 Threads

I'm reviewing transformers and I have some confusion over the current s is for secondary and p is for primary I know that Vs = Vp(Ns/Np) and Ip = Is(Ns/Np) So when you have a load across the secondary terminal you get your current through Vs/Rload. But does this mean for current in...

Hey guys, Been struggling with this for ages any help would be awesome. In Electrical engineering; Suppose you have a balanced multiphase star system with a given line voltage. The impedance of each phase is also know. If one of the coils is short circuited, calculate the line...

How Eddy Currents Produce Attractive Electromagnetic Forces--Maglev Hello, I am working on a paper about maglev systems and am trying to describe attractive electromagnetic suspension systems, but I am having a little trouble exactly visualizing how this works, which from what I have read is...

Homework Statement 50 volts, 60 Hz http://peecee.dk/upload/view/363429 I have to find the current through R, C, and L. Total current. Totalt impedance. Homework Equations I=(U/Z) The Attempt at a Solution See picture: http://peecee.dk/upload/view/363430 For I_R it must...

Homework Statement Find the phase angle between i1 = -4 sin (377t + 25) and i2 = 5 cos (377t - 40) The Attempt at a Solution I first made i2 in terms of sine: 5 cos (377t - 40) => -5 sin (377t + 50) => 5 sin (377t + 230) Now to make i1 positive as well: -4 sin (377t + 25) => 4 sin...

I'm attempting to figure out the total current induced in a hollow metal tube as a result of the EMF due to a constantly varying magnetic flux through its cross-section. Faraday's law of induction states that for an infinitely thin loop of wire in such varying magnetic flux has induced EMF...

Homework Statement An alternating current source is connected to a resistor to form a complete circuit. The oscilloscope settings are: Y sensitivity 4.0v per division Time base 1.0ms per division (i)determine peak voltage of the a.c source (ii)Hence...

I wrote a program to graph the change of 2 currents in an electrical curcuit over time. Circuit and the graph is on the link below. I have the results but I am not sure about it. Do you think the graph roughly makes sense? I have the equations for di_1/dt and di_2/dt and can write them if the...

Homework Statement A solid cylindrical conducting shell of inner radius a = 5.3 cm and outer radius b = 7.9 cm has its axis aligned with the z-axis as shown. It carries a uniformly distributed current I2 = 7.1 A in the positive z-direction. An infinite conducting wire is located along the...

I am currently trying to check the formula for the chiral current of the Dirac equation for a plane wave solution (found here ), that is, j_{R}^\mu = \psi_R^\dagger \sigma^\mu \psi_R j_{L}^\mu = \psi_L^\dagger \sigma^\mu \psi_L With \psi_R = I( \cosh(\frac{\theta}{2}) + \sigma^i...

Let's say a shielded cable is in the vicinity of noisy environment with plenty of EMI. How to go about cancelling the common mode currents, so that the magnetic field gets cancelled. It's pretty simple in case of differential mode currents. The mag field from the forward current and return...

Hi all, i have this clarification i have one voltage output card and it has got 8 output pins and each pin can source around 120mA (5V), but i have to drive one external circuit which requires around 1A. so my question is it possible to short all the 8 output pins so that i can get 8 * 120 =...

Homework Statement If a uniform current with current density s flows around a tube of radius a-- so it is a surface current, how might I find the magnetic field at some arbitrary position vector r?*Homework Equations Biot-Savart? The Attempt at a Solution I am guessing Biot-Savart? Or is...

Please teach me this: In QFT book of Peskin&Schroeder write: J_{\mu}(x)J_{\nu}(0)~C_{\mu\nu}^{1}(x).1+C_{\mu\nu}^{q^{-}q}q^{-}q(0)+C_{\mu\nu}^{F^{2}}(x)(F_{\alpha\beta}^{a})^{2}(0)... I do not know how to expand the product into this series. Thank you very much for your kind helping.

Homework Statement A current of 4.05 A is located 5.93 cm along the x axis, that is, at the point (5.93,0.00) cm. A current of 4.00 A is located 3.88 cm along the y axis, that is, at the point (0.00,3.88) cm. (These currents flow parallel to the z axis, with a positive current flowing in the...

Please teach me this: In chapter 18.4 Peskin&Schoeder(QFT) they consider the annihilation of electron and positron to hadron.Ignoring the mass of the electron,we have: σ(e^{+}e^{-})=(1/2s)ImM(e^{+}e^{-}→e^{+}e^{-}). We have...

Homework Statement Pretend you have three light bulbs in a parallel circuit and one light bulb goes out/removed so that there two light bulbs remaining. Does current of the entire circuit increase, remain same, or decrease after the one of the bulb is removed. The answer is decrease...

Hello, my name is Stefan and I am a twelfth grade high school student working on an extracurricular project which I will present and be ranked(individually; non-competitively) on. I hope to achieve the best possible score and plan to put a lot of work into it. I have a little over a month, which...

Homework Statement "Determine the currents in the various branches" Homework Equations The one I am stuck on is 6. The Attempt at a Solution I know there is 3 equations, I believe one of them is I1 + I2= 3 and a second is 4= 2I3+I2 ?? but I am not sure if that is correct...

Homework Statement Find currents I1-I6. I'm really looking only for the equations though... Homework Equations V=IR The Attempt at a Solution I tried to set up equations for the nodes and loops: Node a:I_2-I_6-I_3=0 Node b: I_3+I_5-I_1=0 Node d: I_1-I_4-I_2=0 Loop 1...

Homework Statement A single phase transformer has the following rating : 120kVA. 2000v/100v, 60 Hz with 1000 primary turns. Determine: a.Secondary turns b.The rated primary and secondary currents Homework Equations Vp/Vs = Np/Ns The Attempt at a Solution a. I have used...

Can magnet fields deflect displacement currents? Could displacement currents be made to propagate in spirals like those in a cyclotron? Do they travel close to the speed of light? Can they be focused into beams? Can they transmit electrical energy at a distance? Are they subject to the same...

Currents and the "quantum" effective action Hi all, I've been reading Burgess' Primer on effective field theory: arXiv:hep-th/0701053v2. I can't follow the reasoning here: I could maybe begin to make sense of this if I were allowed to assume that −(δ\Gamma/δϕ) is the sum of 1PI irreducible...

Hi everyone, I'm writing a novel in which a character "electrifies" water. He sends electric currents through the water to fend off a monster. So obviously the current must be high in volts and amps. My question is, what would be the easiest way to do this? So far, the best thing I can come...

If it is in inverting or non-inverting configuration, will the input resistance increase the mismatching of the bias currents, or will it only increase the error voltage? Please Explain like your talking to an idiot, I need to write an essay on this, and I don't know what to do! Also how...

Hello, So a topological insulator can induce a magnetic field when an electric charge is near to it (I can give a reference if necessary), but the thing is, the paper interprets the origin of this magnetic field as being the hall currents on the surface of the topological insulator. Now I...

Straight wires carrying DC currents... Dear Forum, when will two straight wires, both carrying a DC current, not feel any mutual magnetic force? What reciprocal orientation do they need to have? It looks to me that they will always feel a magnetic force if they are parallel...

Hello. I have been running some simulations on CMOS inverters. When I change the channel dimensions, I noticed something interesting with the drain current -- the smaller the channel dimensions (say around 3μm x 3μm) the simulated drain current is very close to the predicted theory drain...

Homework Statement An infinitely long cylinder, of radius R, carries a frozen-in magnetisation, parallel to the z-axis, M=ks k-hat, where k is a constant and s is the distance from the axis. There is no free current anywhere. Find the magnetic field B inside and outside the cylinder by two...

Homework Statement A current I flows down a long straight wire of radius a. The wire is made of linear material with susceptibility chi(subscript m), and the current is distributed uniformly. i) what is the magnetic field a distance s from the axis? ii) Find all the bound currents. What...

I'm asked to find an equivalent resistance and the current through each branch of the following circuits. (r is a fixed arbitrary value for all resistors in the circuits) Homework Equations V=IR Sum of I at a node = 0 Sum of V about a closed loop = 0The Attempt at a Solution I've been playing...

Circuits / Switches / Currents --TRUE FALSE QUESTIONS (Pic included) Homework Statement Homework Equations The Attempt at a Solution I really have no idea, on going about solving this as I don't have my book with me and the homework is due in a few hours. I'm sure if brief...

Since the tectonic plates ride on the convection currents in the molten mantle, I was wondering if tidal effects could create currents in the molten mantle. The reason I am asking I found this http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html" where it states: This made me wonder if...

Homework Statement A wire of length 95m and a diameter of 2.4mm has a total resistance 1.59Ohms. The potential difference between the ends of the wire is 103volts. A section of the wire 15.5cm in length is bent into an arc of 60deg. The magnetic field is parallel to the bisector of the arc and...

cheers

Hi; first of all I'd like to say I love these forums and they always help me with anything I don't understand. But I can't find an answer for the question I've got in my mind. So if we have the transformer's kVA capacity, the V1/V2 step down ratio (and therefore the turn ratio) and all of the...

Homework Statement A long horizontal wire carries a current of 48 A. A second wire, made of 2.8 mm diameter copper wire and parallel to the first, is kept in suspension magnetically 15 cm. Determine the magnitude of the current in the lower wire. Homework Equations I know that...

I had a lab to do for Physics, and we used a variable voltage source and an electromagnet with 60 turns of copper wire. What is the equation to use to find the magnetic field strength B using relative permeability of a soft iron core? i cannot find this equation anywhere... plus, what is the...

Homework Statement Two batteries and three resistors are connected as shown in the figure Determine the magnitude of the current that flows through 6V battery when the switch is closed. Homework Equations V = IR, Kirchhoff's rules (junction, loop). The Attempt at a Solution...

1. A man points his rowboat north from A to B, straight across a river of width 100 m. The river flows due east. The man starts across, rowing steadily at 0.75 m/s and reaches the other side of the river at point C, 150 m downstream from his starting point. What is the speed of the river...

what's special about a 0.1 to 0.2 volts current? thanks

I didn't know where to post this, but I figured since it has the word "relativity" in my question I would stick it here. V = IR. In a super conductor R = 0 and I = V/R = V/0 which is infinity. This implies an infinite number of charges per second flowing, and hence that the charges are...

The question involves Kirchoff's Rule. I'm having a hard time trying to calculate the currents in the given circuit. I'm trying to solve question number 3 in the attached image (the image on the bottom left hand corner). I have already measured the currents in lab, but I'm having trouble doing...

Homework Statement Hello PF, first time poster here. I don't normally ask for help on the internet, especially for homework, but I've visited this website several times and I've seen nothing but good as I've looked at everyone else being helped, so I decided it'd be worth a try. :) So here's...

hey, could someone tell me if it is possible to measure the angle of twist of a rigid shaft subjected to a torsional moment at one end by using eddy current testing?

I am currently reading "Quantum Field Theory" by Mandl & Shaw (2nd edition). In section 2.4, they give an equation for obtaining a conserved quantity (which leave the Lagrangian density invariant) : \frac{\delta f^\alpha}{\delta x^\alpha} = 0 (2.36 in Mandl & Shaw) In other textbooks that...

Homework Statement Find currents in every loop of the circuit, find voltage on every element,build vector schelude for currents in the circuit. Homework Equations The Attempt at a Solution R1=35 Ohm R2=40 Ohm R5=30 Ohm R6=20 Ohm L4=25millihenry C4=40microfarad...

Homework Statement Electrical energy supplied by a high voltage power has a total resistance of 4 ohms. At the input to the line the rms voltage is 400kV and the input power is 500MW Calculate : A) the min voltage that the insulators which support the line must withstand without breakdwon...

Homework Statement http://img827.imageshack.us/img827/2602/thecircuit002.jpg This circuit is made out of 3 resistors and an ampmeter A whose internal resistance is Ra = 10 ohms 1) Calculate the flow going through the ampmeter where R1 = 20 ohms, R2 = 30 ohms, R3 = 50 ohms 2) Come...

How would I calculate the magnetic flux density of the magnetic field generated by eddy currents induced in a circular plate? I decided it would be reasonable to approximate this by considering the flux density of a current loop. However, it is my understanding that eddy currents are induced...