Current Definition and 1000 Threads

I am curious what happens if you draw DC power to a load, but as it approaches the load you chop the load connection say with a SSR or switch. The power will be traveling near the speed of light, following the wire toward the load. When the load is chopped by a switch just before the pulse...

So I'm having a little trouble getting to the solution to this question so here's my attempt at a solution and I'm not seeing the issue with it 1. I calculated the B-field due to the long wire (approximating the distance from the dipole to be equivalent to that in the centre since r>d) B=...

Does anybody know what the 1/10 meaning is in the current rating description for a fuse holder? 1/10-30A 600V For No. of Fuses For Fuse Current, A Voltage Wire Connection Type For DIN Rail Size, mm Features 1 1/10-30 600V DC/600V AC Screw Terminals 35 Covered Terminals...

I will first calculate the magnetic flux of the coil in motion. $$\frac {d\phi}{dt} = -\frac {dB_{loop}}{dt}A = -\frac{d}{dt}(\frac{\mu_o}{4\pi}\frac {2\pi NR^2I}{(R^2+z^2)^{\frac{3}{2}}})A$$differentiating in terms of ##z##, we get $$\frac {d\phi}{dt} =(\frac{\mu_o}{4\pi}\frac {6\pi^2...

How does changing the core of the solenoid affect the current induced in the loop?

Hi! I've been struggling with this. Original exercise here: Find the value of Iy when R=0. And the value of Vx when R is infinite. For the first part of the question I did this since R=0: I've tried to solve this circuit and I get that Iy and I5 are 0 A, and this can't be possible since Iy...

While I was going through "Introduction to Electrodynamics" by David J. Griffith I see the line "Current is a vector quantity". But we know it doesn't obey the vector algebra (addition ). Then how it can be a vector?... Please help me

The videos from Veritasium explaining permanent static magnets and electromagnets were quite good I thought… But they have me a little confused with regard to the origins of magnetic fields generated by an electric current as opposed to a permanent static magnet from say iron. 1. An...

In a circuit with a set resistance, let's say 1 ohm, the current flowing through the circuit is the same as the supply voltage. Why does an increase in voltage at the supply cause the electrons to flow faster?

Homework Statement Moderators note: link removed. All images should be uploaded to PhysicsForums. Homework Equations V=IR Series in parallel Series in current The Attempt at a Solution I managed to get the current and voltage of R1 and R2. I've been trying to get the next one R3, but haven't...

Homework Statement L = 20mH = 20 x 10-3 H i = 40 mA for t≤0 i = A1e-10,000t + A2e-40,000t A for t≥0 The voltage at t=0 is 28 V. I have to find the equation for the voltage for t>0. Then I have to find the time when power is zero. Homework Equations v(t) = L* di/dt p(t) = L*i* di/dt The...

The Biot-Savart law which describes a magnetic field created by a displacement current: $$\frac{dB}{dV}=\frac{\mu_0\epsilon_0}{4\pi}\frac{\frac{∂E}{∂t}×r}{r^2}$$ What's the relativistically co-variant form of this equation? Is the introduction of speed of light propagation delays enough, or...

We all know a moving charge generates a magnetic field. A moving charge also generates a displacement current ∂E/∂t. Is the magnetic field generated entirely due to the presence of the displacement current, or is there an independent, separate effect which contributes to the magnetic field?

1. Homework Statement The ideal battery in Figure (a) has emf = 7.7 V. Plot 1 in Figure (b) gives the electric potential difference V that can appear across resistor 1 of the circuit versus the current i in that resistor. The scale of the V axis is set by Vs = 18.9 V, and the scale of the i...

I assume this forum to be the appropriate one, since the real problem is about covariance rather than electromagnetism. In electrodynamics in a curved background, the relation ##F^{\mu \nu} = A^{\mu , \nu} - A^{\mu , \nu}## stays in terms of ordinary derivatives. So, in particular ##F_{,\mu...

I will make some assertions and then phrase a question , please correct me if necessary. So the tokamak works like a transformer where the primary is a coil winding while the secondary is a torus which contains plasma which being electrically conductive forms the secondary winding? The toroidal...

I'm working on a Scifi novel, and trying to make it somewhat...scientific! Any advice is appreciated. Here's my question: I'd like to write about a situation where a body of water is purposefully kept under electric charge for years on end. This body of water would vary in size and depth, but...

Homework Statement If the current flow, in a branch of a circuit, is a function of say (√(x + 2)-2)/(x-2) (or any such that give an indeterminate form at a certain value) of an input source current x. What current will be flowing on that part of the circuit, when the function become...

I was reading The Feynman Lectures on physics http://www.feynmanlectures.caltech.edu/I_23.html chapter 23, section 4. In it he derives the equation for current when inductor, resistor and capacitor is connected in series with an alternating voltage source, he derives this equation:-...

Homework Statement Homework Equations - The Attempt at a Solution Here's my work : When I add the DC current source , it shows a red dotted line and won't connect to other elements . Any help would be greatly appreciated !

Homework Statement In perspective to the photoelectric effect I found following question: Electric current is charge flowing per unit of time. If we increase the kinetic energy of the photoelecrons (by increasing the energy of the incident photons), shouldn’t the current increase, because the...

Let's assume a 2:1 transformer which has a 100V Source connected on the primary circuit and has no/negligible resistance, on the secondary circuit a 5 Ohms resistor is connected. Using the 'Impedance Transfer/Reflection' method, the primary circuit would act as if there was a 25 Ohms resistor...

Lets say I am analyzing a simple AC voltage source with a resistor. In the positive voltage peak then I will use V and I say current is flowing clockwise. When I am analyzing the -Vpk iteration then do I make the current counter clockwise too or do i keep it clockwise? Thanks.

Hi all, I'm trying to wrap my head around the physics behind the current that initial flows when a voltage step is applied across a capacitor. Namely, why does a large current initially flow into a parallel plate capacitor, but a large initial current does not flow if the capacitor is replaced...

I read about electric armor (also known as dynamic armor or electric reactive armor) that can protect armored vehicles from shaped charges of anti-tank weapons and I want to know if its feasible today. according to wikipedia: [Moderator: please don't do this without a link. The link is The link...

I am looking for small signal BJT that has very low leakage current when the base is biased at about 0.2V. I have issue of transistors drawing collector current when the base is at about 0.25V that is way less than the normal turn on of 0.6V to 0.7V. I am currently using BC546 or 556, and KSA992...

Ladies & Gents, Instead of applying current to a non-magnet to induce magnetism, is it possible to apply current only to temporarily de-magnetize a magnet (natural or man-made)? This would seem to use up less electricity, especially since the default mode for a desktop application I'm working...

Dear Sirs, Maybe this is general knowledge, but I couldn't find the answer where I looked, so please bear with me. Consider a circuit consisting of a mechanical generator (some spinning magnets and coils) and a wire across the generators output. At some point the wire gets hot and starts a...

Homework Statement The diagram below shows a circuit where; R1 = 5.0 Ω, R2 = 8.0 Ω, R3 = 1.0 Ω, V1 = 16.8 Volts, V2 = 1.5 Volts, and V3 = 39.6 Volts. What is the value of I1? In solving this problem, initially pick the current directions as shown. If the actual current turns out to be in the...

Homework Statement It's best if one looks at the picture of the circuit diagram. What we're given is a current of 0.25 A and two resistances of 20 and 30 ohms. Homework Equations Kirchhoff's Voltage Law, Kirchhoff's Current Law, Ohm's Law The Attempt at a Solution My attempt at a solution...

Alright. So I'm getting two different solutions depending on how I look at this problem, and I know one is correct but I don't know why the other would be incorrect. So, given this general circuit of a constant current source driving an RC circuit in parallel: Now, what they tell me in class...

I'm calculating current through a resistor by measuring a single current pulse, integrating it and multiplying it with its frequency. This would correspond to calculating an arithmetic mean. I also tried calculating RMS of this waveform, using GNU Octave, and was a bit surprised by the...

Where does the LQG approach stand right now? What are its biggest successes and failures? Does it have any known difficulties that might be "fatal"? What major questions (on the fundamental level) are still open in the approach, and is there "momentum" toward solving them? In particular, is it...

Howdy, Pretty elementary question, I think. Looking at Ohm's law, current is I=V/R For a given voltage (let's use 120 for typical U.S.A household) at what resistance will current actually cease to flow (equal zero)? To clarify and expand on that: I am confused about whether a system with an...

hi everyone! i am not into physics, but need it now,i am a programmer workin on an IOT project...so kinda need help. i want to use a capacitor to see what passed between two plates...knowing, it is the change in dielectric after certain intervals...how do i measure the change at the other...

Hello all: I was seeing all the news about rover mission , but catch my eyes that rover was stopped due to a dust storm , maybe it's solar panels is covered with dust and the batteries charging in its minimum for that reason . is that possible best H

The current definition of Gravity is: The force of attraction between bodies as a result of their mass. Gravity affects both the space and time of the area surrounding a mass, diminishing with distance, so is the current accepted definition truly accurate? Do I have the correct definition and if...

Hi. I have two questions about the following video with a 200'000 V Van de Graaff generator: At 5:57 he touches ground, apparently feeling nothing. He explains this with a very low current and proceeds that the current from a 120 V outlet is high and might kill you. But with ##I=U/R## and...

Hello, Basic question: what is the difference between a current and a voltage amplifier? Naively, in principle, I would think that if either quantity is magnified, the other will be also magnified simultaneously. How can we magnify current without magnifying the voltage and vice versa? Thanks...

Hi all, I have been reading Griffiths' book on Electrodynamics and have come across a point (image attached below) where he states that volume current densities are 0 on the surface of the current-carrying objects. He then uses these properties in pretty-important integrals. However, I...

Consider a very simple idealized circuit, with a constant voltage emf, perfectly conducting wires and a resistor all in series. There is a potential drop across the resistor, given by Ohm's law: ##V = -IR##. I have read on the Internet that many people say that the potential drop is caused by a...

Hi all! I was thinking if it is possible to revert the Faraday effect. If I have a magnetic field, it interacts with EM wave (light) by changing its polarisation. Can I got a variable magnetic field interacting with polarised light so that I can get induced current in a coil? I can understand...

Hi. The blue curve shows the idealized behaviour of the detected current vs. the acceleration voltage in a Franck-Hertz experiment: It appears that the underlying behaviour is quadratic, why? I calculated the time for an electron to reach the grid at distance ##d## from the hot cathode to be...

We make an infinitesimal Lorentz transformation of the Lagrangian and require it to be invariant. We then arrive at the following expression. $$\epsilon^{\mu\nu}j_{\mu\nu} = P_{\mu}\epsilon^{\mu\nu}X_{\nu}$$ which can be written as $$\epsilon^{\mu\nu}j_{\mu\nu} =...

Homework Statement The diagram shows a circuit used for the investigation of photoelectric emission. The two electrodes E and F are made of different metals. The work function of electrode E is higher than that of electrode F. Which of the following graphs show the variation the current...

I have to test a Current transformer. I read knee point is a point at which 10% increase in voltage leads to 50% increase in current. As there are different classes of current transformer (cores), how it is decided what/how much will be the knee point voltage of that core.

I know this is not ok but just for a few seconds or minutes and for the purposes of "boiling" the acid a little to make it even, break some sulfate deposits off the plates and recover a young battery that was neglected for a few months, what current would a 12 V / 480 A / 85 Ah lead-acid car...

2019 is the smallest number that can be expressed as sum of 3 squares of prime number in 6 different ways 2019 = $7^2+11^2+43^2$ = $7^2 + 17^2 + 41^2$ = $13^2+13^2 + 41^2$ = $11^2+23^2+37^2$ = $17^2 + 19^2 + 37^2$ =$ 23^2+23^2+31^2$

The photograph above this sentence is a photograph of a simple 2 leg circuit of alternating current with a light switch and a light bulb. I know how alternating current constantly switches direction from line 1 to line 2 and then goes from line 2 to line 1, etc. In the diagram in the above...

Hi. I am practising for my test and since I don't have the correct answers, I don't know if what I'm doing is right. I tried to solve this problem, can you check it and correct if it's wrong? Here's a clearer picture of the circuit. I suspect Uab isn't right, but am not sure. Thanks...