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.

View More On Wikipedia.org
  1. Magnetosphere

    Need help with the magnetic field generated by this current distribution

    Homework Statement A DC current is flowing between two electrodes through a iron disk medium. Positive is attached to the copper shaft of the disc and the negative is attached to the outer brass periphery of the disk. The radius of the disk is 2,54mm (1 inch) and the height of the disk is 1cm...
  2. S

    What happens to the current in a loop when a magnet approaches

    Homework Statement There is a magnet that approaches the loop as in the figure. There is already a counterclockwise current in the loop. What happens to the current in the loop? Is my reasoning correct? Homework Equations The Attempt at a Solution Since the flux is increasing in the loop...
  3. Boltzman Oscillation

    Electrical Engineering: What is the current through this?

    Homework Statement I have a current source of 2mA in parrallel with a resistor of 9.2kOhm and a short. What is the current through the short? Homework Equations The Attempt at a Solution I always thought shorts had an infinite amount of current but maybe I do not quite understand the...
  4. Luxucs

    Faraday's Law with Zero Resistance Current Loop

    Hi there, I was recently helping a friend of mine with a fairly standard electromagnetic induction problem (a basic sketch of the set-up is attached) where we have a current loop with resistance ##R## moving through a magnetic dipole and had to roughly sketch out the current induced in the loop...
  5. jra12222

    Current Division Rule: Solving for Currents

    Hi all, I was working the following example: where I need to find the currents. I tried solving using the traditional V=IR => I=V/R, and then I tried with the current division rule. However with the current division rule the answers don't match. Also according to the answers on the book the...
  6. V

    A few questions concerning voltage, current and resistance

    [ mentor note: post adjusted to conform to homework template and some spellings fixed ] 1. The Problem I have some few questions that connect voltage, current and resistance. Imagine that we have a circuit that consists of a battery (5V), 2 resistors. Now once we close the circuit, battery...
  7. fluidistic

    I Understanding L&L's argument, constant current in a crystal

    I'm trying to go through chapter III of the vol.8 of Landau and Lifshitz series. (Fortunately the book is uploaded to the archive.org, I guess it is in the public domain.) At page 87 ( << Archive.org link deleted by the Mentors because of copyright violation >> ), they speak about the Joule...
  8. Spinnor

    B field of 1/2 infinite solenoid, equivalent current confguration

    I have wondered if there is a symmetric current configuration that gives the magnetic field of a half-infinite solenoid. With some thought I think I came up with such a configuration of current loops that produces the same magnetic field as a half-infinite solenoid Suppose we have a large but...
  9. H

    Current State of Nuclear Fusion Power

    When I was an undergrad doing research in a university lab, the director of the lab also consulted at a Nuclear Fusion company. I remember like it was yesterday him making a statement that commercial Nuclear Fusion was going to be a reality within 10 years. That was 1977. What happened? Lack...
  10. C

    The Current State of Mathematical Rigour

    Sorry if that title doesn't match up well with my question. I think it captures roughly what I'm wondering about. My uncertainty is to do with how much of mathematics is certainly true. Like, if I picked up any undergrad or grad textbook in mathematics, would everything in it be true based on...
  11. Clara Chung

    Bound current of a magnetized object

    Why is the current of the boundary uniform?
  12. Y

    Automotive Motor constants at high current

    Hi, This is a general question: Do the motor constants KV and KT stay constant at high current? Thanks
  13. Shivang kohlii

    Current through source in AC circuit with R & LC in parallel

    Homework Statement In the circuit diagram shown , Xc = 100 ohm , XL = 200 ohm , R = 100 ohm , the effective current through the source is ? Homework Equations Z= √( R^2 + ( XL - Xc)^2) Vrms = Irms/ ZThe Attempt at a Solution I tried to draw the phaser diagram and calculate the relation...
  14. Freddythunder

    Current Surge Capacitor Calculator

    Hello friends... I'll jump right into the deal here.. I pranked a friend by putting a raspberry pi into a yoda head like the one on his desk. There's an intro video: and the prank itself: if you are intrigued. Everything in the head runs off 3 AAA batteries. 1 raspberry pi zero w, 1 small...
  15. Krushnaraj Pandya

    Current through capacitors in parallel

    Homework Statement In the given circuit at t=0 S is closed then at time t, i1/i2 a) is constant b) increases c) decreases d) first increases then decreases Homework Equations V=IR, Q=CV The Attempt at a Solution At t=0, capacitors act like closed switches, so I2=2I1, where I2 and I1 are the...
  16. Abimbola1987

    Joule's first law - kinetic energy of electrical current

    Dear Sirs, If I take this explanation as being true "The heat is generated on the microscale when the conduction electrons transfer energy to the conductor's atoms by way of collisions." So a "current" must have a quantum of kinetic energy going into the conductor (resistive element) and a...
  17. W

    Charging a battery and monitoring the current w/ an instrumentation amp

    Homework Statement Homework Equations CMRR = Av/Acm Acm= Δ/R , Δ = (2 x Tolerance of Resistor).R The Attempt at a Solution I have to admit I am a bit confused by the premise of the problem. My understanding is Vout is used to vary Vcharge in some way, so that Icharge is always 1.3 A. Then...
  18. DJ_Juggernaut

    I Is current in a wire frame-specific?

    There is current flowing in a wire. An observer at rest with respect to current, says there is a magnetic field (B) around wire, due to current, I. [Biot-Savart law]. Now switch to someone moving at the speed of current. The current appears stationary to this someone. Therefore this someone...
  19. Akash47

    Why we use the conventional direction for current flowing?

    I often get confused that why we have to use the ancient idea for the direction of current flowing.I have come to know a very weak reason for it.It is said that when current was first discovered,it was assumed that the current flows from the positive region to the negative region(using the idea...
  20. J

    A typical monthly utility rate / Current and resistance

    Homework Statement A typical monthly utility rate structure might go something like this: $1.60 for the first 16 kWh, 7.05 cents/kWh for the next 34 kWh used, 5.02 cents/kWh for the next 50 kWh, 3.25 cents/kWh for the next 100 kWh, 2.95 cents/kWh for the next 200 kWh, 2.35 cents/kWh for all in...
  21. R

    Powering an LED via Induced Current

    Homework Statement As the title suggests, I have a school project where I’m supposed to design a hand shake flashlight using AWG 34 copper wire, a niobium cylindrical magnet, hard paper (sort of like cardboard), and a red LED. The goal’s to get the red LED to light. My teacher gave some hints...
  22. W

    Ground current for a voltage regulator

    Homework Statement Homework Equations 3. The Attempt at a Solution [/B] Currently working on the question relating to the ground current on the voltage regulator, 7805 (data sheet included below) I am very much unsure what to calculate here I'm assuming the current to ground is the input...
  23. Aishikdesto

    Nature of charge at the junction of a composite wire

    Homework Statement Please help me answer thew question in the image.[/B] Homework Equations Current Density J=conductivity X Electric field[/B] The Attempt at a Solution As the current density depends on the conductivity of the material through which the electrons constitutuing it are...
  24. F

    Eddy Current Brakes: where to with its current?

    I've seen a documentary about the Yukon Route Railroad. Some trains are run by old steam engines (with Diesel). They also equipped their engines with eddy current brakes and said, that the resulting current is conducted into resistors and via thermal energy removed into air. I assume that...
  25. Kevin J

    What is the current flowing in this zero-Ohm path?

    The 2 Ohms on the voltage source is its internal resistance, what is the current flowing through the (0 Ohms) Path?
  26. Kevin J

    How is current induced in superconductors?

    Assume resistor R/heated segment is 5 Ohms, while the path in the right hand side remains 0, thus, total resistance is 0 Ohms, my question is how could current be induced if potential difference is 0(due to zero total resistance) Or is it probably because of the batteries internal resistance?
  27. S

    Lenz's law: Current induced in a split loop by a changing B-field

    Homework Statement We have a circular loop of wire, with AB is another wire which is also the diameter of the circular loop. The direction of magnetic field is perpendicular to the loop, into the plane of paper. The magnetic field strength is decreased at a constant rate, without changing the...
  28. S

    Current through circuit when switch is open

    Homework Statement Seven equal resistors, each of resistance 2Ω are connected with a battery of 3V in a circuit shown. If i1 is the current when the switch S is open and i2 is the current when switch S is closed, find the value of i1/i2. Homework Equations 1)Equivalent resistance formula...
  29. Kevin J

    Why does current choose the short circuit path?

    I've seen answers saying that electricity takes path of least resistance, I know this and there is no need to explain this for me. A forum's answer told me that the electrons initially flow through to the path with resistance and eventually becomes congested (redirecting the remaining electrons...
  30. D

    Did I count this current in a circuit correctly?

    This i a test question and we are not allowed to use a calculator, so I was wondering whether I did everything correctly, since the I1 = - 1/7. I am supposed to find out I3, but stopped at I1, since the result is a bit tricky. 1. Homework Statement R1 = 10 ohm, R2 = 20 ohm, R3 = 40 ohm I3 = ...
  31. J

    Current Flow Through Lamps in Circuits

    Homework Statement [/B] State and explain whether or not current will flow through the lamps in these circuits Homework Equations None The Attempt at a Solution I am confused with figure 6 as my explanation is different from my textbook's answer. My textbook says: "Figure 6 – the lamp is...
  32. Lapse

    Current Through an Inductor at time t

    Homework Statement Homework Equations [/B] V = 1/L di/dt I = Io x (1 - e^(-t/L/R) Tau = L/RThe Attempt at a Solution [/B] Ii = 0mA ; If = 1mA Vi = 1V ; Vf = 0V Tau = 15uH / 1k Ohms = 10ns If my above is correct, then voltage and current equations through inductor should be as follows...
  33. P

    I Why is Displacement Current Excluded from Four-Current?

    To put this in another way, is there some reason from first-principles as to why we have j as the spatial component of the four-current rather than the total current density which includes the displacement current? Has anyone tried to see what the experimental consequences of this would be? Kevin M.
  34. J

    The direction of induced current and magnetic field produced

    Homework Statement The figure below shows a small circular loop of wire in the plane of a long, straight wire that carries a steady current I upward. If the loop is moved from distance x_2 to distance x_1 from the straight wire, what will be the direction of the induced current in the loop and...
  35. Lapse

    Integral for Current through an Inductor -- Not Working

    Homework Statement [/B] Calculate, and plot along with (on the same plot) the voltage seen below, the current flowing in the following circuit using the integral relationship between the voltage across an inductor and the current through the inductor. Verify your hand calculations and plot...
  36. kolleamm

    Why is it said that high current is dangerous? Why not Watts?

    From what I've read, it says that high current is dangerous. So my question is if you had 1v and 10amp, would it be more dangerous than 10v and 1 amp? Shouldn't they be the same? Why don't we say high watts are dangerous?
  37. F

    Why Do Moments Balance in a Faraday Disk but Not the Forces?

    Hi to everybody! Please: can you help with this problem? A conductive disk with a radius a = 20 cm, with negligible moment of inertia, rotates around its horizontal axis. The disc region around the radius is inserted in a magnetic field B = 0.75 T perpendicular to the disk itself. A mass is...
  38. S

    Electric current flowing in a power transmission line

    A cable of resistance 12 Ohm carries electric power from a generator producing 250 kilowatt at 10,000 volts. Calculate the current in the cable. Solution using P=VI I=25A but using P=I^2R 250000=I^2×12 I =500/root 12 Amps What is the reason for the different...
  39. Abdul Quader

    I Probability current density

    In order to check if a quantum particle crosses a barrier or not, isn't calculating ##|\psi(x)|^2## enough in that particular region ? Why do we need to calculate probability current density for that matter?
  40. archaic

    Current Through R1 and R3: Explained

    Hey guys, in the picture below, the current flowing through R1 is the same flowing through R3 right? And hence we have R1 and R3 in series? In this second picture R2 is going to cancel out because apparently that's what happens when you have a branch containing components parallel with a wire...
  41. Lapse

    Engineering Design Circuit to Convert Current to Voltage | LTSpice Also

    Hello, We just finished up midterms and I actually did well--got an A. However, somehow between the midterm (class before last) and last class we jumped to creating a circuit with a diode. I am pretty lost. 1. Homework Statement Homework Equations Voltage / Current = ResistanceThe Attempt...
  42. ErikZorkin

    I Is Chronology Protection Still Relevant in Modern Physics?

    What is currently the common opinion on Chronology Protection manifested by Hawking almost 30 years ago? There does not seem to be any fully accepted no-go result for Thornian time machines. Energy conditions can be violated in QFT, semi-classical results suffer from counter-examples, Novikov's...
  43. AlenKovac

    I All current 'hints' towards Dark matter not being "matter"

    I want to start by saying that I'm in no way trying to say that Dark Matter isn't a real pehonomenon in space. I also have no intention to sway one way or another. However, I feel like most scientiests are swaying towards the 'dark matter' is some kind of WIMP or such. It's much easier to read...
  44. F

    Measuring the current from a micro generator affects its output?

    I am performing an experiment where I have built a scale model of a wind turbine, and am measuring the current it can produce with a micro generator. I am using a standard multi meter and the micro generator is DC. I do not know much about the topic, but whenever I start measuring the current...
  45. M

    Sensing current in a conductor

    If I have 120 vac power cord and I wrap a coil around one of the conductors, will a current/voltage be produced in the coil? If so what are the equations that could be used to characterize this arrangement? I.e., how many coils, what size wire, etc. To produce a certain voltage in the coil?
  46. G

    Transmission line: leakage current differential equation

    Homework Statement I have a coaxial cable with internal conductor of radius r1 and external conductor of radii r2 and r3. The material of the conductors has a conductivity ##\sigma_1##. Between the conductors there is a imperfect dielectric of conductivity ##\sigma_2##. Consider the...
  47. Eclair_de_XII

    Studying My current study habits aren't cutting it for me at the moment

    I had a test today on my linear algebra class, and it's safe to say that I didn't get more than a seventy percent on it. I got the first two problems of the test down, but the last problem asked me to prove something involving linearly independent sequences, how if a vector isn't in the span of...
  48. Jonathan1218

    Does low current make a light dimmer

    If two light bulbs have the same voltage but one with a lower current does it make one dimmer than the other? I’m confused why lights in parallel circuits don’t get dimmer even tho there is less current. Thx for replying
  49. T

    Determining the direction and origin of the Hall current

    A Hall current arises when electric currents transverse to a magnetic field exist. In this figure (found online), the Faraday current appears to be going upwards due to a magnetic field pointing into the page, but is this correct? I'm largely just trying to understand the origin of the Hall...
  50. Sid55

    Buck-boost converter output current limiter

    How can I get around current limiter of this buck-boost converter to achieve a lot higher current output than max rated current output for a very short amount of time ? Does having high continuous current discharge power source at the input help it in any way ? This buck-boost converter offers...
Back
Top