Current Definition and 1000 Threads

In this seemingly simple circuit, applying KCL, I get the current in the shorted branch as ## 3E/(2R) - 2E/(2R) = E/(2R) ## but some sources suggest that it is ##5E/ (2R) ## which is right and why?

Very basic question. Consider a 3-terminal device with terminals say A,B,C. Kirchhoff Current Law (KCL) and Kirchhoff Voltage Law (KVL) establish two relationships between the 3 currents entering the terminals and the 3 terminal's voltage pairs respectively. So we have 2 equations in 6...

Hi, having difficulties in this problem. Looking for ideas. For now, I think the combined voltage of source and coil should be bigger or equal to EMF, for the battery to get charged: ##U+L\frac{dI}{dt}\ge EMF## the current going through the coil, I think, would be...

Hello , In the system below there is a mode i am trying to couple. at weak coupling I get a certain surface current responce and in stronger coupling I have different responce as shown below. How can I see from the surface currents where can i improve the coupling in my model?

Theoretical thought experiment, trying to evaluate batteries in parallel, connected with non ideal conductors that have same current draw? Trying to understand the concepts here. If I have three identical cells. Fully charged. Same age. Charged and discharged the same amount of times. Each cell...

The statement is: Find the currents of the circuit after the switch S is closed. I solved it by EDO (ordinary differential equations) and then I tried to solve it by Laplace and they gave different answers.

Is it true that for a charged capacitor with a DC potential across it, the actual surface charge depth is very shallow, just few angstroms or few atomic layers so to speak, because if the plates of a parallel plate capacitor are made from a metal like copper where the free electron number is...

Need some help in understanding the current ratings of wires. I had asked about this in another thread, and learnt that power ratings of wires depend on numerous factors. To simplify things for me, I could successfully dig out the product datasheet from one of the notable companies in my country...

I assume that electric current is made up of moving electric charges. If this hypothesis is correct, then the current that flows through a coil is made up of accelerated charges. I am not interested in evaluating the situation quantitatively. My question is conceptual. Does a coil that conducts...

My wire is 16 AWG (264 cores of 40 AWG) with 0.010 FEP Insulation. I have the insulation and the MJF nylon that it is touching melting! How much current would I need to have to get to these temperatures with this wire? This wire is inclosed inside the MJF nylon case, so figure for no air flow.

Hello, I am trying to create a MHD boat. With my magnet and my generator, which generates a current of 10A, I can create a rapid flow. However, the cable connecting the electrodes to the generator generates a force that prevents my boat from moving forward. I've tried different types of cable...

My first thought was that as the heat current ##I_H## is going to be constant at any cross section of the rod, by the equation of continuity, as the area of cross section is constant throughout the rod. So using: (where ##R_{total}## is the total thermal resistance of the rod) $$I_H =...

How does the current flow in this circuit and what is its actual true path, regardless of any directions in the figure? What does the “5i” above the dependent source mean, and does the current flow according to the dependent source or the independent source? Are the two resistors 2 ohms and 6...

The picture of the question and my try: Would it be possible for someone to double-check my answer for accuracy? I would greatly appreciate any feedback or guidance on this matter.

I just saw a question saying there's an induced current in a dc motor. i always thought dc motors' electromagnetism is separate from the ac generators' electromagnetic induction? if there's really an induced current, how will the overall system work then? wouldn't the rotation be opposed? also...

Hi, PF, this thread is meant to be an introduction to the principles of ##DC## and ##AC##, but I'm very much insecure about the rigurosity of my point of view, so I prefer to post at the lounge. There it goes: fasten seat belts :smile: The textbook ("Pre-university Physics Principles", by the...

Why does current not split into the middle junction? I notice that this is true regardless of the values of the resistors.

Hi Friends! Regard the 2 kW electric kettle and 60 W incandescent bulb - what happens if we plug them in series? It is the problem I often ask my students somewhere at the end of the term to check if they remember basic "laws" about electricity. Recently I started collecting some exercises on a...

My attempt: $$d\vec{B}(r) = \dfrac{\mu_0}{4\pi}\dfrac{Id\vec{l}r\sin{\theta}}{r^2}$$ $$d\vec{B}(r) = \dfrac{\mu_0}{4\pi}\dfrac{Id\vec{l}\sin{\theta}}{r}$$ $$ \sin{\theta} = \dfrac{y}{(x^2+y^2)^{1/2}}$$ $$ d\vec{B}(r) = \dfrac{\mu_0}{4\pi}\dfrac{Id\vec{l}}{r}\dfrac{y}{(x^2+y^2)^{1/2}}$$...

What would happen if we tried forcing a bar magnet into a magnetic field created by a solenoid (look at the picture)? Assume that both the bar magnet and the solenoid are isolated form any other source of a magnetic field. What I am thinking: First of all, if we tried forcing the north side in...

Hello, I need to calculate the expression for a current on two dipoles separated as shown in the attached full task . I need to present a solution,lets take the simplest case. Theta_in=0 I need to find the expression for the currents on the dipoles...

Hey Everyone, I am not an electrical engineer I am a biochemmie and I am here for your help. I have been learning household wiring and troubleshooting electrical wiring problems in my house for the last few months and I am stumped on an HVAC issue and would really appreciate some insights from...

I've been really confused on how electricity and circuits work 1. If eletrons "slow down" inside a resistor (or wire, I'm considering it's resistance to be ≠ 0) because of collisions with the lattice, then wouldn't the electrons pile up? The charges accumulating doesn't seem to be good. 2. Some...

I first thought of imaging techniques, because the setup reminded me of it, but i have only ever seen those of electrostatics. If i for example add a current in the opposite direction and with the opposite heigth of the surface the fields dont cancel out at the surface, i think. What is the best...

I followed the following approach which is also the listed solution: First of all, from Ampere’s circuital law, we get: ∮B⋅dl=μ_0I Here, I is the enclosed circuit in the circular Gaussian surface of radius c and its value will be: I=J⋅πc^2 Here, J is the current flowing per unit cross-sectional...

Problem: An annular disk consists of a sample of material with thickness d, inner radius ##\displaystyle R_{1}##, outer radius ##\displaystyle \ R_{2}##, and electrical conductivity ##\displaystyle \sigma##. Let the radial current ##I_0## flow from the inner periphery to the outer periphery of...

I've done internet searches on this. There doesn't seem to be any agreement. Is the direction of the drift velocity in a wire the same as the (conventional) current? [AI Chatbot reference deleted by the Mentors]

I have a lot of doubts regarding this . Let's say the resistance is ##R## where the net interaction force becomes zero . So , the current flowing should be : $$i=\frac{V_{\circ}}{R}$$ Will charges be induced like in capacitors? If yes then let's say ##\pm q## is induced and the length of the...

$$I=\frac{q}{t}$$ $$=\frac{4Q}{T}$$ $$=4Qf$$ My answer is (a). Is that correct? Thanks

Initially the current is non-zero therefore we have a magnetic field present, and at the end there is no current therefore there is no magnetic field present. When we open the switch, and the current drops to 0, there is a change in the magnetic flux of B, as the field from A has gone. This...

Accelerating electric charge produce EM wave Does constant DC current in curved wire produce EM wave, because el.charge has radial acceleration in curved wire?

Hello, I have derived an expression for ##\vec J## in a particular, unusual physical problem in 2D. The expression is different from ##\vec 0## everwhere in the material except at at least two different points. Can I conclude that the only way for this to occur is that ##\vec J## itself decays...

Hi. Does displacement current create a magnetic field by Biot-Savart? I googled and found contradictory answers. Also, in the presence of an external magnetic field, is it meaningful to calculate a Lorentz force acting on displacement current? What does the force actually act on then?

I know that a voltage difference doesn't necessarily imply current flow, but all the explanations I seem to find of that either say that that happens because the resistance is infinite, or there is nothing connecting the two points in question (the two are basically the same thing, as I...

Quick question, is 5 milliamps at household voltage like 240 dangerous? See many conflicting views on this, official accounts state that on an electric shock chart, 5ma is nowhere near the level needed to cause any damage but some electricians on reddit say with low body resistance even low...

A wire coinciding with the X-axis carries a current I1 in the direction of increasing x. A second wire is parallel to the Z-axis at a distance R, and carries a current I2 in the downward direction as indicated in the figure. The magnetic field at point P (0, 0, R) is: (options and diagram in photo)

In this video at 0:38 man say that unbalance current flow increase magnetic radiation far away, even few streets away from source.. 1. Why radiation increase in these situation? 2. Is every system subject to that phenomenon and when unbalanced current happend? 3. Will emf meter show this...

In this situation I would have two solenoids facing each other, such that both ends are north for example, and when activated they are actively experiencing repulsion, I know that the magnetic field of both would decrease in strength, but would there be any affect on the electrical input of each...

According to the special theory of relativity the electric and magnetic fields observed from a charge distribution should depend on the relative motion of the observer. For example consider a linear arrangement of point charges which are fixed relative to each other. An observer who is...

Image from Wiley Intro Physics Textbook sample problem This was the given problem. In the diagram, one can see that the current flowing into each battery equals the current flowing out of each battery. Is this always the case, and why? If there was only one battery, I guess it could be...

This post is somewhat of a continuation of this other post. I would like to better understand induction and be able to link the electrical equations with Newton's. For reference, this is a paper about the Eddy Current Damper I would like to study first. I think these components are very well...

This is the proposal, except the two middle voltages are 110V, not 12V. Say the max switch-on inrush current of XFMR1 is xA with the secondary open, would the value change significantly in the above arrangement, with the secondary of XFMR2 open?

1. Consider this diagram. Does the bulb light up? The equation I=V/R tells me no, but if there is a potential difference between the two points, surely current will flow and the bulb will light? As there is nowhere for the electrons to go, I assume it will only light for a very short period of...

Suppose the ring is held stationary such that its area vector points upward. The magnet moves downward toward the ring at constant velocity north-pole first. (The starting position is shown in the figure.) Since ##\vec{B}## is downward while ##\vec{A}## is upward, ##\Phi_B=\vec{B}\cdot\vec{A}##...

What is the difference between a current-carrying coil and a solenoid?

(1) https://www.youtube.com/results?search_query=relativity+and+electromagnetism (2) If I understand this correctly, then, well, shouldn't all current-carrying wires exhibit a small amount of positive charge?

I recently heard the narrator of a podcast state that the current of almost all rivers in the world flows from North to South. The narrator said the Nile River is one of very few rivers in the world that flows from South to North. I cannot figure out why almost all rivers in the world have a...

I assumed that the radius is referring to a major R like in the image below. I plugged all the values (except for length) into the equation B = µ*N*I/2πr to get 155.6 A for the current value. I am unsure if this is the correct value or if radius refers to minor r of solenoid, in which case a...

The following circuit is: Going clockwise the current ##I_1## goes through resistor ##R_1## and voltage ##V_11##. Current ##I_2## goes through capacitator ##C_1## and ##R_2##. Current ##I_3## goes through resistors ##R_3## and ##R_4##. Current ##I_4## goes through resistor ##R_5##, but from...

A wire loop accelerates from position 1 to position 5. It enters an area of a homogenous non changing magnetic field B. Rank the induced currents in the loop starting from the biggest. in solutions it says I4>I2>I1=I3=I5=0 but i dont understand why