What is Electric current: Definition and 172 Discussions

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. F

    Electric current passing through closed loop

    Homework Statement (sorry for possible notation errors, that might arise during the translation) Why an electric current passing through a closed loop, can be defined only in stationary conditions? Homework Equations The Attempt at a Solution I think that the reason is that, if the...
  2. P

    How is electrical current delivered into houses?

    How is the potential difference done? How do they make electrons move? Do they use electrical field using positive (to atract them) or negative charges (to repel them)? Do they use variables magnetic fields?
  3. Amr Elsayed

    Electric current misconception

    Hello everyone, I have a problem which is a conceptual misunderstanding concerning electric current. I understand that different charges attract and like charges repell, I want to know what really happens inside the wire so a lamp lights immediately when we press on the light button. an...
  4. Karan Punjabi

    Magnetic effect of electric current

    I'm confused that what is the main difference between the magnetic field produced by electric current and the magnetic field produced by a real bar magnet? As per my knowledge the magnetic field of Current does not have any poles. Then how a solenoid and a bar magnet's magnetic field be similar...
  5. Vicol

    Electric Current: How Does the Battery Generate Voltage?

    Hello again :) I've got a serious problem. Generally I know why current flows (free electrons and voltage). But some days ago I was considering about regular battery and electrical circut. Free electrons in wire flow along circut, ok, that's fine and understandable. But how does battery...
  6. H

    Non Ideal Batteries in Electric Current

    Homework Statement A circuit is constructed with five resistors and one real battery as shown above right. We model. The real battery as an ideal emf V = 12 V in series with an internal resistance r as shown above left. The values for the resistors are: R1 = R3 = 57 Ω, R4 = R5 = 75 Ω and R2 =...
  7. heavystray

    Function of Commutator: Reversing Electric Current

    Hi, so i want to ask what's the function of the split between the commutator? my guess is to temporarily separate the opposite electrons flow between the coil and external circuit after the half cycle? so that's why the current is reversed? please i really need someone to explain how the...
  8. Jacekmai

    Electric current propagation through living tissue

    Wave propagation speed or velocity of propagation (VoP) of a transmission medium is ratio at which the wavefront of the signal passes through the medium to the speed of light in vacuum. For example, copper has a wave propagation speed ~0.951. What is a wave propagation speed through a living...
  9. C

    Electric Current in a Capacitor: What is it Called?

    How is the current that pushes electricity through the space between the two plates of the capacitor called?
  10. K

    Electric current function of time

    Homework Statement ##i=20\sin(377t)## is the current function. in the time interval 0-1/120 sec what is the charge that passed Homework Equations $$q=\int_0^t i dt$$ The Attempt at a Solution $$q=\int_0^{1/120} 20\sin(377t) dt=\frac{20}{377}\int_0^{3.14} \sin x dx$$ $$q=-\frac{20}{377}\cos...
  11. N

    Calculate electric current in a resistor

    Homework Statement calculate the electric current in the 20 ohm resistor The Attempt at a Solution I have no idea where to start, but i thought maybe you should calculate the voltage first and then the voltage over the 20 ohm resistor.
  12. P

    Calculating Current in a Series-Parallel Circuit with Resistors

    Homework Statement Two 16 Ohm resistors connected in parallel are then connected in series to a 10 Ohm resistor. The entire setup is connected to a 9 V battery. What is the current through the 10 Ohm resistor? Homework Equations V=IR I1+I2=It 1/Rt= 1/R1 + 1/R2 The Attempt at a Solution So I...
  13. C

    Question about speed of an electric current

    Hello! Supposed I had 2 identical copper wires, I'll call them A and B. I insulate wire A with whatever the standard wire insulation is, and leave wire B alone (uninsulated). I'll now send an identical signal (same voltage and power) through each wire. Will the current be identical at the...
  14. D

    Problem in Magnetic Field and magnetic effect of electric current

    I read in class 10. I am having problem understanding magnetic fields, magnetic flux,magnetic flux density,magnetic field strength,magnetic permeability and strength of magnetic field produced due to a straight and closed loop current carrying conductor at a certain point at a certain distance...
  15. S

    Need electric current modulator

    Could you advise me, which type of device could be purchased in general electronic stores (or at least in specialized ones) and which are capable to modify electric current in wide spectrum? Desirable in small power range. Such as to set a pulse width, harmonic, frequency, pulse duration, power...
  16. L

    Exploring the Potential of Photon-Based Currents

    The photon is the force carrier of the electromagnetic force, I'm not talking about photonics but hasn't the effect of every electric current dc or ac ever been due to photons acting only? In theory couldn't we have an electron-less current due to only photons but still with the same effects?
  17. S

    Get magnetic field if you know electric current

    Homework Statement In other words, I have an equation: ##\nabla \times \vec B =\mu _0 \vec j##, where ##\vec j = (f(x,y),g(x,y),0)##. I need to find ##\vec B##.Homework Equations The Attempt at a Solution I tried to write each component separated, but I don't see how to continue, since all...
  18. kartikwat

    Electric current in household wires

    See, we know that different electrical appliances in our house require different amount current to work .now first if some appliance is working which requires less current then less current will be passing through wires but when we use electrical appliance which uses high current then high...
  19. kartikwat

    Electric current in bulk material

    Why is it that in bulk matter , though molecules are closely packed electrons are no longer attached to individual nuclei It is mentioned in 6th line of 3.3
  20. T

    How to calculate force of electric current on magnet

    Hello, It is my understanding that a moving magnetic can induce an electrical current, and that conversely, and electrical current can move a magnet. I believe that this is the basis by which speakers work (changing electric field causes vibration of the magnet that generates the sound)...
  21. KingCrimson

    What is it that causes electric current to drop after a step up ?

    what is that causes the current in the wire that has a stepped up voltage * in the transformer , the wire with more coils * to have a lower current ?
  22. P

    What is the Electric Current Produced by Solar Wind Protons Near Earth?

    Homework Statement Here is the Task: The solar wind streams off of the sun in all directions at Speeds of about 400 km/s. It contains roughly equal number of electrons and Protons. Near the Earth we find in a cube with a side length of 1 m about 8.7 * 10^6 Protons. The velocity of These...
  23. Entanglement

    Electric Current in an open circuit

    I'm still a beginner at Electricity and electromagnetism, I'm wondering If we connect a wire to a positive terminal ONLY , why won't the electrons flow to the positive terminal of the cell as electrons are negatively charged, I have been days thinking about it and I need a clear convincing...
  24. H

    Gauss law and electric current

    According to the Gauss law, the extra charges gather on the surface of a conductor. When there is a current in a conducting wire, do the charges only move on the surface of the wire or we have current also inside the wire? If we also have current inside the wire how is it compatible with Gauss law?
  25. D

    What carries the energy in an electric current?

    Electric current is often analogized to water under pressure in pipes. When water is moving through a pipe, the energy of the system is the potential energy of whatever is giving the water its pressure -- a column of water, say -- and the kinetic energy of the water molecules as they move...
  26. M

    Why boundary condition in steady electric current?

    when we electric field between two conductors in certain direction the current density should pass in its direction why current density direction change at boundary although the direction of electric field is the same for both conductors
  27. A

    Variation of electric field to produce electric current

    Theoretically , a change in either electric or magnetic field will cause a current to flow , i am already familiar to Faraday's law of electromagnetic induction , so i tried to search about producing a current using a varying electric field, didn't find anything , i found an interseting...
  28. S

    Phys Chem Heating water with electric current

    Homework Statement 86.9g of liquid water at 304K is heated by 1.75A passing through 24.7Ω for 104s what is the final temp Homework Equations its been a while since i did physics so bear with me if i get something mixed up here q=mCs,pΔT q=ItΔψ ψ=pot dif so isn't that just V from...
  29. E

    When two equal electric current flow opposite to each other in a wire

    Let us consider a circuit... There's a 10 V battery... A Rh(resistor with changeable resistance) and another battery is connected in parallel in the circuit... Now current I (due to the 10 V battery) divides into two parts when it reaches the parallel connection... Let's note them by Ir and...
  30. J

    How much current does a 1500W electric appliance draw in a 120V circuit?

    Homework Statement The power rating of an electric appliance is 1500 W. How much current does this appliance draw when it is used in a home electric circuit ( V= 120)? Homework Equations P= VI The Attempt at a Solution P= VI => I= P/V => I= 1500W/120V = 12.5A Is this...
  31. I

    Electric current in the human body

    You mostly hear about electrons as being the vehicle of an electric current because we think of wires and metal. However, if an electric current traveled through the human body, it would be in the form of ions, right? But what happens at the interface between body and wire? I am guessing that...
  32. I

    Electric Current: Finding Energy lost in a capacitor

    Homework Statement E& M Purcell, 3.11 A 100-pF capacitor is charged to 100 volts. After the charging battery is disconnected, the capacitor is connected in parallel to another capacitor. If the final voltage is 30 volts, what is the capacitance of the second capacitor? How much energy...
  33. P

    Equation for Induction of Electric Current in Magnetic Field

    I am looking for something that should be relatively simple to find, but as such, I have not been successful. I know that an electric current can be created by moving through a magnetic field. I have found equations that indicate this can be based on the velocity and the length of said object...
  34. W

    Why electric current is a SI base unit?

    hi, why electric current is a SI base unit - why not couloumb?
  35. S

    Can an Electric Current Travel Instantly Across a 3000000km Long Cable?

    Hi, all. There's a thought flashing through my mind yesterday. Sorry for my lack of knowledge. The thought must be something wrong. Can anyone correct it? Thanks If there is a 3000000km long power cable, and the cable is pulled to 3000000km away from the earth. A power source connected on...
  36. B

    Heat produce by electric current

    I recently finished a lab experiment on heating effect of an electric current(heating water by running current through a resistor). I did two runs of the test first at 2 amp and second at 3 amp. The first run shows a small % error however the second run gave me 26% error. What would explain the...
  37. L

    Semi-Safe Electric Current in Water without explosions?

    Hello, I am currently trying to create a sculpture that involves having a live electric current running through water inside of a sterilite tub. The way I would like to go about doing this is very crude, I would like to take an extension cord, cut the end off of it,and stick the live end...
  38. A

    Direction of electric current in a conductor

    ok so here is the question number 45 and its second part and this is what i did I have a c magnet drawn with the north pole and the bottom opening right. And the magnetic field lines running between the two polls (virtically) And I have a conductor running between the poles...
  39. L

    Could a coaxial cable be used for electric current instead of radio signals?

    http://en.wikipedia.org/wiki/Coaxial_cable http://en.wikipedia.org/wiki/Poynting_vector Could a coaxial cable be used for electric current instead of radio signals? 'For example, the Poynting vector within the dielectric insulator of a coaxial cable is nearly parallel to the wire axis...
  40. A

    Electric current - High voltage power lines buzzing

    Electric current -- High voltage power lines buzzing Question: High voltage power lines string along roads often give off a faint buzzing sound. Use what you know about the motor principle to explain the source buzzing. ok, so i have no idea how to approach this. I've never heard...
  41. M

    What is the magnetic effect on an electric current.

    I was just wondering and I looked and couldn't find anything. I suppose i could experiment it my self but anyway. If I had a wire with an electrical current flowing through, just say 10Amp; and I pass a magnet near the wire, would it slow the current down? Or increase the resistance? I know...
  42. C

    Why do magnetic fields appear when an electric current passes through a wire?

    I've checked Wikipedia for answers but can't find any. I'm learning electromagnetism in school now. I don't know why this happens and so I can't understand the lessons! Can anyone tell me why? Thx :)
  43. J

    Electric Current as a function of time

    Homework Statement 8. An electric current in a conductor varies with time according to the expression I(t) = 100 sin (120*pi*t), where I is in amperes and t is in seconds. What is the total charge passing a given point in the conductor from t = 0 to t = 1/240 s? Homework Equations...
  44. A

    Electric Current: Why Does It Flow at Light Speed?

    why electric current flows at speed of light when we know that current is due to the drift velocity of electron which is only few km/s(i think)?
  45. T

    Electric current is found when Menthos is put in Coca cola

    Few years ago, we have known about the phenomenon that Coca cola is overflow severely when a piece of Menthos candy is put inside. I replicate this experiment, with a multimeter is used to measure the current. With my surprise, the needle vibrates to show that an electric current is...
  46. D

    Trying to apply electric current to plasmas in motion.

    How do you represent a certain mass of plasma (ions and free electrons) traveling inside a containment from point A to point B as "I", electrical current? Trying to make a connection, Doug Ettinger
  47. S

    Voltage across coiled wire with varying electric current

    A varying electric current running through a coiled wire induces an emf across the coil. The voltage measured by a voltmeter across the terminals of the coil: (a) is smaller or larger than the emf, depending on how fast the current changes. (b) is larger than the emf. (c) is equal to the emf...
  48. B

    Electric Current: Positive/Negative Charge Movement in Conductor

    "An electric conductor carrying electric current from left to right is placed in a downward magnetic field. It is observed that there are positive charge on the front of the conductor and negative charge a the back. If the electric current is reverse, flowing from right to left, then the...
  49. S

    Electric current? how many electrons?

    Homework Statement A net charge of 49 mC passes through the cross-sectional area of a wire in 12.0 s (a) What is the current in the wire? _4.1E-3_ A (b) How many electrons pass the cross-sectional area in 1.0 min? ______electrons Homework Equations I=Q/t The Attempt...
  50. S

    Electric current transmitted over great distances.

    Kind of a basic doubt here, but it has been nagging me for a while now. The electric field generated by a power station is a non-conservative one, and it varies as 1/r with respect to the distance of a point from the source.( I am assuming this statement is accurate.) So what I don't get is how...
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