Current Definition and 1000 Threads

An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In a electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons.The SI unit of electric current is the ampere, or amp, which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit Electric current is measured using a device called an ammeter.Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conductors, they cause Joule heating, which creates light in incandescent light bulbs. Time-varying currents emit electromagnetic waves, which are used in telecommunications to broadcast information.

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  1. JCMacaw

    Meaning of fuse current rating for fuse holder

    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...
  2. Zack K

    Current induced on a coil by a changing magnetic flux in another coil

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  3. diegbarrientos

    Influence of Core Change on Current in Solenoid Loops

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

    Engineering Help me finding the current in here please (Circuit analysis)

    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...
  5. A

    What is Current? I know it is a scalar but I found something weird....

    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
  6. M

    Origins of magnetic fields from permanent static magnets versus current

    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...
  7. M

    Why does an increase in voltage cause faster electron flow?

    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?
  8. P

    Finding the current and voltage for each resistor

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  9. N

    Deriving Voltage from the Inductor Equation

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  10. T

    I Relativistic form of the displacement current using the Biot-Savart Law

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  11. T

    Magnetic Field of a Moving Charge and the Displacement Current

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  12. MedEx

    Finding the Current in a Resistor in a Closed Circuit

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  13. G

    I Electromagnetic Curr. in Curved Spacetime: Questions Answered

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  14. A

    How Does Tokamak Plasma Heating Work and Can Reactive Power Improve Efficiency?

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  15. callie123

    Writing: Input Wanted Electrified Water: Feasibility and Applications

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  16. R

    When current flow reach indeterminate form

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  17. Adesh

    How to solve a complex equation to get the current?

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  18. F

    Implement a DC current source - simulink

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  19. O

    Current produced by photolectrons

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  20. K

    B How a Secondary Resistor affects the Transformer Primary Side?

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  21. Boltzman Oscillation

    In AC analysis do I alternate the current and voltage?

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  22. T

    Why does current initially rush into a capacitor?

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  23. F

    Is Electric armour feasible with current technology?

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  24. Y

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  25. J8675309

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  27. J

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  28. R

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  29. Abdullah Almosalami

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  30. H

    Charge and current, RMS or aritmethic mean?

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  31. M

    A Current Status of Loop Quantum Gravity: Successes, Failures & Open Questions

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  32. E

    At what resistance does current cease to flow

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  33. S

    A change in the dielectric constant changes the current or voltage?

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  34. hagopbul

    B Is the Rover Mission Halted Due to Dust-Covered Solar Panels?

    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
  35. Antony Death

    B Is the current definition of gravity accurate?

    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...
  36. G

    Let current from a Van de Graff generator flow through you

    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...
  37. F

    What Is the Difference Between Current and Voltage Amplifiers?

    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...
  38. W

    Why Are Volume Current Densities Zero on the Surface of Conductors?

    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...
  39. fluidistic

    Charge distribution in a resistor with a current

    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...
  40. R

    Reversing the Faraday effect to get an induced current

    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...
  41. G

    I Franck-Hertz: Overall behaviour of the current

    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...
  42. H

    A Derivation of the Noether current - Lorentz Transformation

    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} =...
  43. S

    Correct graph of current vs voltage (photoelectric emission)

    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...
  44. Manoj Sahu

    Why do Current Transformer cores have different knee point voltages?

    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.
  45. gasar8

    Why Does the Majorana Vector Current Vanish?

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  46. J

    What current would a 12 V lead-acid battery draw from a 24 V charger

    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...
  47. kaliprasad

    MHB Interesting property about 2019( the current year)

    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$
  48. F

    In a circuit, what causes current to go from L1 to L2?

    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...
  49. stipan_relix

    How to find power and voltage using the mesh current method?

    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...
  50. I

    Calculating Short Circuit Current: Tips & Advice

    Good evening to everyone! I'm pretty new in this kind of job, so every help or advice will be helpfull and I will appreciate it. I know that short circuit current from picture in attachment depends on impedance and reactance of Source MV, transformer example (10kV/0.4kV) and cables. So if I...
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