Current Definition and 1000 Threads

  1. D

    Engineering Parallel/Series combination of PV modules

    The solar irradiance incident on the PV modules is 5 kwh/m^2-day.The current each module can provide is 5 A and the voltage due to the separation of charge carriers is 18 V under standard conditions (1 Sun=1000 W/m2) so we would have to connect two modules in series to exceed the voltage of the...
  2. skibidi

    What is the maximum current in a RL circuit using V=IR?

    I found the time constant using L/R and got 0.62s (3.6H/5.8ohms) I found the initial current V/R and got 4.086A (23.7V/5.8ohms) I(f) = 4.086A(1-e^(-0.5s/0.62s)) Then I plugged it into the equation and got 2.26A and it was wrong
  3. T

    I Is the magnetic field from this current rotationally symmetric?

    Imagine a very large disc with current converging to it's center as $$ I=- \frac{k}{r} \hat{r}$$ Obviously ##\theta## is absent in the equation so the magnetic field by this current should look the same no matter which angle one is observing. Then does this mean that the magnetic field is...
  4. S

    I Question: Interpretation of Current and Magnetic Field Using Relativity

    The current in a wire is said to produce a magnetic field and a force on a charge. It is said that the correct way to interpret the effect is because of relativity. So does that mean that that the most basic non-relativistic equations that offer basic calculations of the forces and fields are...
  5. Sibilo

    I Does the Skin Effect cause charge to accumulate on the surface of a conductor?

    good morning gentlemen, I would like to ask you a fairly simple question but which I am unable to resolve. Then considering the "skin effect", which involves an increase in resistance to the passage of current with consequent generation of eddy currents, this leads to an accumulation of charges...
  6. K

    Is grounding necessary when running off of batteries?

    Hi all, playing with fancy e textiles and I wish to run a current through it. I don’t want to use mains, or d cell batteries. Can you point me in the right direction what components I could use and also how to get away with any grounding as it’s just a small area to put a current through...
  7. student_man

    Engineering Current change after inserting thin conductive foil into resistor

    I tried splitting it up into 4 individual resistors, adding them up (each side serially and then both sides with each other as parallel) and then using V=IR but it ended up being the same current as the original. (The answer should end up being (9/8)* the original current)
  8. H

    Ohm's Law confusion -- How to handle an incandescent bulb?

    I know that Ohm's Law gives me the answer of 0.25 A but what I don't understand is how is it ok to use Ohm's Law when I know that the lamp doesn't obey the law? I know that as the current is increased through the lamp, the resistance increases due to temperature rise which, I am told, makes it...
  9. Hak

    Coaxial semi-infinite solenoid and superconducting disc

    I have no idea how to deal with the problem. Do you have any hints, please?
  10. PhysicsTest

    Are the Battery Capacity Calculations for Electric Vehicles Correct?

    Battery Capacity = Current * Time Power = 400 * 750 = 300000 Watts V*I = 300000 I = 300000/300 = 1000 Amps Battery Capacity = 1000 * 1 = 1000AH. Are the calculations correct? Why the battery capacity is defined in Amps?
  11. D

    AC generator, current and ground

    Hi, Let's say we have a basic AC generator, where a single wire is rotated within two magnets: Due to the electromotive force, a voltage is generated so that Va - Vb = 120V. Let's now ground Vb side directly to earth, while leaving Va still open: We can say that Vb = Vc = 0V and Va...
  12. P

    Electrical Help with detecting current/voltage with a coil and a spinning magnet

    Playing around with electricity and magnetism. Well, trying to anyways. Wound some wire up and down the length of a 4" screw several times. Thought when I spun the magnet close to the coil I would get a detectable amount of current on my voltmeter. Anyone know why I'm not reading anything? I...
  13. casparov

    Calculate the Magnetic Vector Potential of a circular loop carrying a current

    Can someone explain what exactly happens at (4) ? I do not clearly follow, except that there is some cosine law going on? I also do not really understand why at (3), r' doesnt have a z hat component, but I can live with that.
  14. A

    Bidirectional current switching with single type transistor

    So here is my dilemma. I have a test setup with multiple coils all lined up in parallel in such a way that one end of each coil is connected together while the other is connected to a switch (mosfet) the switches then connect each coil to ground but that ground can become + based on which coil...
  15. gurbir_s

    I Angular momentum associated with a current carrying circular wire

    How should I calculate the angular momentum carried by a current carrying circular wire? Is it correct to consider the angular momentum of the electrons moving with drift velocity? Like ##L = n m_e v_{drift} r## where ##r## is radius of the loop, and ##n## is total number of electrons moving in...
  16. L

    Discharging a capacitor -- Calculate the current as a function of time

    Hi, I am not sure if I have calculated the task b correctly. I always interpret an open switch as an infinitely large resistor, which is why no current is flowing through this "resistor". So there is no current in the red circle, as it was the case in task part a, but only in the blue circle...
  17. ananonanunes

    Finding Current in Resistors & Charge of Capacitor

    Suppose the switch has been closed for a long time so that the capacitor is fully charged and current is constant. a)Find the current in each resistor and charge Q of the capacitor. b)The switch is now opened at t=0s. Write the equation for the current for the resistor of 15kΩ as a function of...
  18. S

    I Can Conducting Current Through a Bar Magnet Cause Movement?

    Following the Picture below, If I Conduct current through Permanent magnet Bar and hold the battery still. Will the magnet move in any direction ? Thank you.
  19. Jarvis323

    Current and Future AI Threats to Humanity and the Human Response

    There has been an explosion of discussion among experts about the evolving/growing dangers of AI and what to do about it. This debate has gone public, largely due to the recent success of generative AI, and the rapid pace of improvement. As an example, AI models which can generate images based...
  20. M

    Current in a circuit without external resistance

    It shows 0 and it's obvious why. I have another question. Can I say that in this circuit the current is maximum and it equals to ##\frac ε r = 2A##?! Someone asked me this question: Are A and B two ends of the wire? If yes, Why is there current in the wire even though the potential difference...
  21. J

    How does the presence of a cube resistor affect current flow in a circuit?

    I would think that it is 2 A (6/3 because there are three wires the current can go to), but this does not seem to be correct.
  22. P

    I What is the benefit of measuring both direct and reverse current?

    What is it's benefit?
  23. G

    Power dissipated by a resistor on a coaxial cable

    I need help with part c. My solution: Is there an other way to do this other than dimensional analysis? P.S "dr an infinitesimal radius", it ofcourse should be dz.
  24. G

    Surface current on a spherical superconductor

    I need help with part b. My solution: Have I done it right?
  25. Astronuc

    History History of Railroad Safety - Spotlight on current derailments

    The recent spate of train derailments has put the spotlight on derailments and railroad safety in general. Railroads are generally a safe means of transporting cargo, including hazardous chemicals, and in fact railroads are safer than a decade or two ago. Yet, one catastrophic accident...
  26. G

    Using complex numbers to solve for a current in this circuit

    First I solved 4+j3, which I squared 4 and 3 to equal 16 and 9 then I added them to get 25 and then I got the square root of 25 = 5. Then I plugged it back in to the equation. [50/(5)(50)+100] x 150 to get 50/350x 150= 1/7(150)= 21.42. I've attached the correct answer.
  27. J

    Determining Current Direction in a Charging RC Circuit

    After the switch is closed, current flows clockwise from the battery to resistor R1 and down through the switch. I don't understand the reasoning for the following: the current from the capacitor flows counterclockwise and down through the switch to resistor R2. How do I determine the direction...
  28. T

    I Are voltage and current waves in transmission lines an artifice?

    The operation of a transmission line is based on the axial propagation of electromagnetic waves between the two line conductors. However, the study of the transmission lines does not focus on E and B waves but on voltage and current waves. It is considered that there are resistance...
  29. PhysicsTest

    Engineering Is My Understanding of the Current Amplification Circuit Correct?

    I have taken portions of a schematic for amplifying the current I1, this I1 current is the phase current from one of the legs of the inverter. The output vout1 is the amplified voltage, again given to a micro which has internal opamp. Is my circuit understanding correct? When I give I1 = 10...
  30. PhysicsTest

    Engineering Voltage and current calculation of circuit

    I am trying to find voltages and currents of the below circuit, 3.3 -22000*I2 - 2200(I2-I3) = 0 3.3 -24200*I2 + 2200*I3 = 0 -> eq1 -(10 - I3)*1500 - (I2 - I3)*2200 = 0 -15000 + 1500*I3 - 2200*I2 + 2200*I3=0 -15000 - 2200*I2 + 3700*I3=0 -> eq2 Solving equations 1 and 2 i get I2=0.38 Amps...
  31. abdulbadii

    Failed function within SMPS giving weak current

    What is the very common culprit component and what is its function within SMPS having weak current, far weaker than its rating while its voltage is always perfect?
  32. haha0p1

    Using Kirchhoff's law, deduce the value and direction of the current

    3 A+ 2 A = 7 A+ I I = -2A How the current can be in negative direction? If the sign if negative, doesn't it mean that the current will move towards the point P? Also If I am taking the 2A to be positive then Kirchhoff's law isn't satisfied as 5A≠7A
  33. Engineergn

    Snail Fan Motor High Current Issue

    We producing industrial steam boilers. We also produce snail fans for our boilers. The problem is our fan blades are a little bit heavy for our motors until blades get warm. "We can't use more powerfull motors cause of energy saving." We control our fan motors via drivers and our fan blades...
  34. S

    Battery circuit current flow when charging

    I would like to know when a alternator is charging a battery is the current flow a series opposing circuit......?
  35. Evari5te

    Solving Current & Power in 4 & 3 Wire Circuits

    My thoughts were I could use mesh current analysis to derive equations for current hence power in each case in terms of ωC and R, set the equations for real power equal to each other and solve for R. While ωC are known I opted to leave them as letters thinking this might make life easier when...
  36. PhysicsTest

    Optimizing an Op Amp Current Sense Circuit: Are the Calculations Correct?

    TL;DR Summary: Trying to solve the op amp current sense circuit as per the schematic. I want to solve the below current sense op amp circuit, Are the calculations correct? As of now i modified the circuit by removing the capacitors, i will add them once the above circuit calculations are...
  37. Kyuubi

    Speed of Current in a coaxial cable

    I've found the inductance and capacitance per unit length in a long coaxial cable. I even clearly see that if I multiply the two, I can get the speed of light. How do I begin to find the current wave and its speed though?
  38. Kyuubi

    Current on Infinite Periodic LC Circuit

    I wrote down the equation of motion for In(t) and I'm trying to match it with infinite spring mass system equation solution. In the spring mass system, we consider A to be the equilibrium length of the springs, and we can thus write Xn(t) = X(nA,t) and put it back into the equation of motion...
  39. K

    Current through Flat Sheet or plate

    Current flow through a wire is considered (or assumed) to be flown uniform across the cross section of the wire (or is it more near skin? or at core?). However I wonder if that's the case with a sheet or plate or circular disc. e.g. If I apply voltage at two opposite corners of the square or...
  40. M

    Question about the Microscopic Model of Current

    Why do they say uniform conductor? Many thanks!
  41. S

    I Deriving expression for resistance in terms of current density

    Is there a way to obtain equation 9.42 (I is current, j is current density, and sigma is conductivity) in the following image (from Modern Electrodynamics by Andrew Zangwill, the part on electromotive force) besides using V=IR and substituting the line integral of j/conductivity for V? The...
  42. supak111

    Calculate current in a 120 VAC circuit with a series 10uF capacitor

    Hi can someone tell me please how much current is passed though below circuit: 120 AC 60Hz mains power going through a 10uF 500v capacitor in series
  43. B

    I Emission of light from incandescence of metals

    a. We know metals emit EM radiation upon heating or electric current. I'd like to understand more fundamentally how this phenomenon takes place, on the basis of the basis of band structure, and which electrons are involved ? b. Classically, charges emit radiation when accelarating or...
  44. G

    Power generated by this current source

    Figure: My attempt at a solution: 1st kirchoff law: $$J=2I_0+I_0=6\, \textrm{A}$$ $$V_1+8=10\rightarrow \boxed{V_1=2}$$ $$V_1=6-V_S\rightarrow \boxed{V_S=-4\, \textrm{V}}$$ We are looking for ##P## generated in ##J## $$V_J=V_1-2\cdot J=2-2\cdot 6=-10\, \textrm{V}$$...
  45. F

    Engineering Use voltage nodal analysis to solve for the current flowing in this AC circuit

    Hi first time using this forum, I have some homework that I am entirely stuck on, can anyone help me with this question? I understand the placement of nodes, and that I need to convert complex numbers, but apart from that I have no idea what direction that I'm supposed to take in this. I don't...
  46. babaliaris

    How does Earth Ground "absorb" electric current?

    This is a topic that almost no one can actually explain from what I found on the internet. This answer https://physics.stackexchange.com/questions/74625/does-alternating-current-ac-require-a-complete-circuit/74999#74999 is the closest I found so far. The idea is how the grounded neutral...
  47. H

    B Voltage & Current: Explaining the Basics for Beginners

    This is a very basic beginner question but one which confuses me. We are told that voltage = current x resistance but I've also read that we can have a voltage without current. But, if current = zero, then if V = IR, V must be zero. Can someone explain where am I going wrong?
  48. A

    A Current status of Tom Banks' Holographic space time?

    Interested in Banks' HST these days, for discussion,here are some abstract and an email from L.Smolin. A recent conclusive paper as well https://arxiv.org/abs/2201.06988 The formalism of Holographic Space-time (HST) is a translation of the principles of Lorentzian geometry into the language...
  49. A

    A Current status of FR type Thought experiments

    Recently I've seen many fixed FR(or Wigner's friend) thought experiments.For example, https://arxiv.org/pdf/2011.12716.pdf is a zero-cited paper that presents a strenthened version of FR ,and claims to have solved its weaknesses.The author claims that it supports the idea that the "C"(for...
  50. A

    Calculate the probablity density and current density of a wavefunction

    i have use time evolution operator to get the wavefunction at any time "t" as Ψ(x,t) = U(t,t1) * Ψ(x,t1) but i don't know how to calculate next part of the question
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