What is Ac current: Definition and 92 Discussions

Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa. In certain applications, like guitar amplifiers, different waveforms are used, such as triangular waves or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. These types of alternating current carry information such as sound (audio) or images (video) sometimes carried by modulation of an AC carrier signal. These currents typically alternate at higher frequencies than those used in power transmission.

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  1. J

    EM field due to a long wire submitted to an AC current

    Hello there, I am having a real stupid moment. In the space XYZ, a long wire is along the Y axis and is submitted to an alternating current I_{0}\sin \omega t. I am trying to establish the equations for the B(t) and E(t) fields along the X axis. I assume that the distance to the cable...
  2. C

    Is AC current analogous to sound waves?

    It is really hard to picture current as a wave. The best explanation I have had so far is that the energy is transferred along the wire as a longitudinal wave of compressions of charge density, just like a sound wave is a longitudinal compression of mass density. so consider an open circuit...
  3. B

    Building an LC Circuit powered by 60Hz AC Current

    Hey guys, So I'm working on this project, and I'm trying to make two coils of different diameters to be tuned to the same resonance frequency. I got the equation ω=1/(LC)^0.5 for the frequency. My thinking was that the frequency of the wall power shouldn't matter because the resonance...
  4. H

    Creating a 1mA AC Current Source with Noninverting Op-Amp Configuration

    Homework Statement Design a circuit based on the noninverting op-amp configuration that functions as a 1mA ac current source. Homework Equations Gain = Vout/Vin = 1 + R2/R1 The Attempt at a Solution I really don't know how to start.
  5. G

    AC Current in unconnected wires

    Hello, My electrician had to disconnect the ground wire from mains distribution box a day ago. And he forgot to attach it back. I did not know it was un-attached. Then in the evening, I touched my computer and got a shock. I used a screw driver type phase tester and checked the ground part of...
  6. D

    B Field Confinement for Toroidal Coils Driven by AC Current

    It is said that toroidal inductors/coils (see http://fa.tu-sofia.bg/te/Brandisky/images/toroidal_coil.jpg ) that are perfectly axially symmetric will completely confine B fields. That is, the B field inside will be nonzero and will circle the toroid, but the B field outside the toroid will be...
  7. C

    Why don't electronics care if it's DC or AC current?

    I understand AC is economic for transportation and easy to produce from converting mechanical energy into electrical energy. However, why don't electronics turn on and off because of this alternating nature of the current? For light bulb, maybe it does turn on and off and our eyes don't have...
  8. K

    Direction of AC current through AC mains

    What would be the direction of the current from the mains till it completes its one full path and the appliance used in the circuit starts working? See attached image.
  9. M

    Calculating Magnetic Field of Solenoid Coil with AC Current

    Hello I want to calculate field of the Solenoid Coil with AC current. For a DC current field is calculated easily from the BiotSavart. What is the process for AC current? Get the L value with RLCMeter in operating frequency? Is there an equation to get the field with...
  10. R

    AC voltage, DC voltage, AC current and DC current

    Hi, I know that existence of AC and DC currents but what exactly the same with AC and DC potential difference. Of-course it was very basic question and i apologize if it annoys any. Please explain the difference only in terms of voltage. Thank you.
  11. C

    AC current, conceptual question, the difference between Iaverage and Irms?

    Homework Statement This is more of a conceptual problem I'm having difficulty getting my head around. What is the difference between Iaverage and Irms for a rectified and non rectified AC circuit? I know Iaverage=(2/π)Imax while Irms=(1/√2)Imax but I don't understand why they are...
  12. M

    Rlc circuit with ac current source

    Homework Statement An AC current source, 1 ∠0° A, with angular frequency 1 rad/s is to be applied to the input terminals of the circuit. Circuit is RLC, the current source is in parallel with a 1F capacitor which is in parallel with a 1H inductor which is in series with a 1Ω resistor. I...
  13. R

    Creating AC current from 6v DC source

    Hello! I'm a long time reader, but this is the first time I've not been able to find the information I've needed already... I have a small electromagnet that needs to have an AC current (it is essential that the electromagnet has a reversing polarity) but the source of power comes from a 6v...
  14. S

    A steel rod and an iron rod is placed inside an ac current soleoid

    What happens? I think nothing should happen since the rods will not get magnetised at all due to the ac current.. Thanks for the help!
  15. S

    Magnet in a AC current solenoid

    when you place a magnet into a solenoid with a ac current it will get demagnetised. So does this mean that the magnetic field will go into the magnet in the opposite direction of the magnet's own magnetic field? and disalign it. meaning will the magnetic field enter the magnet as though it is...
  16. G

    Why does i(t)=dq(t)/dt give the value of AC current only?

    I know the mathematical and geometrical reason, but does there exist a physical interpretation behind this? Thanks :smile:
  17. C

    How would the magnetic field of a solenoid change if it used AC current

    How would the magnetic field of a solenoid change if it used AC current instead of DC current? How would this affect the motion of a charged particle moving from the center to the side of the solenoid? This isn't a homework problem, just something I'm curious about. Hence, there is no "right"...
  18. S

    B field of a wire carrying AC current

    Hi. New to the forums so bear with me. I am trying to calculate the magnetic field at a distance r from a wire carrying a 495Hz signal at 8Vpp and current 0.8mA. Initially I tried ampere's law, but fell into the trap of using the un-modified form (without maxwell's correction). I know that...
  19. timthereaper

    Power Transmission via AC current

    I'm a mechanical engineer and I'm really interested in electrical systems. I understand a fair amount about the basics of E/M and circuits. But no matter how much I read, I can't wrap my head around how AC systems generate power. I do know they work (obviously, right?), but I'm trying to imagine...
  20. S

    Exploring AC Current Flow in Pure Inductors

    if a pure inductor is connected to an AC voltage source! The Back emf in the inductor=Thr instantaneous AC emf! THEN How can the current flow through the inductor if the NET VOLTAGE=0? please explain
  21. F

    Will a Leyden Jar Store AC Current?

    Okay, I was planning on building a Tesla coil for my (high school) physics class. For the high voltage capacitor I was planning on using a Leyden jar, however, after doing some research I only found references to it being used to store an electrostatic charge. Thus, my question is, can a...
  22. PainterGuy

    Understanding AC Current: A Guide for Beginners

    hello everyone, this is diagram from a book:- http://img816.imageshack.us/img816/4671/clipperac.jpg this is same diagram i have modified:- http://img849.imageshack.us/img849/1848/modifiedclipperac.jpg this is truth i don't understand how AC current work. let me tell you what i think of AC...
  23. S

    Force on a conducting ring due to solenoid with AC current

    Homework Statement A long circular solenoid of radius a and N turns per unit length has its axis in the z direction. A small highly conducting ring, or area A, resistance zero but self inductance L, is place with its plane horizontal and its centre on the axis and near the top of the...
  24. S

    How does the voltage on the inductor change over time?

    Homework Statement An alternating current is running through a serially connected inductor(L) and resistor(R). The alternating voltage causing it is: http://upload.wikimedia.org/math/5/a/0/5a0ecaa1432c6cdce653a943b4962a21.png How does the voltage on the inductor change over time? Homework...
  25. J

    Understanding AC Current: A Simplified Explanation for Non-Science Students

    Please remember that I'm not a science or physics student, so please explain as simply as you can. Thanks. In the case of DC current electrons flow from a negative terminal to a positive. A negative terminal is full of electrons and the positive is electron deficient. I'm trying to understand...
  26. M

    Will you get an AC current in this situation?

    Say you have a conductor (a single straight wire) which goes from left to right across your computer screen and moves up and down in periodic motion in a constant magnetic field that goes into your computer screen (see diagram below). (note: you can ignore the computer screen, and you can...
  27. X

    How do I convert a small AC current into DC current?

    I am constructing a small wind generator for a college project. I want the 0.1 V AC output of the generator to charge a battery. To do this, I need to convert the current into DC. I am familiar with things like bridge rectifier circuits, but the smallest diodes I can find have a forward "turn...
  28. W

    Absence of m.field around an AC current carrying wire

    One of my friend says that it is possible that there will be no magnetic filed around an AC current carrying wire but he did,t know about the reason. can anyone give the reason
  29. C

    How does a generator produce AC current?

    I just don't understand how it does, because I never noticed the terminals change positions. I understood how DC generators work, but not AC.
  30. D

    How to check AC current Through multimeter

    Hai Guys... I want to check the AC current by using digtal multimeter.Please give me instruction.
  31. T

    Addition of AC current and compound angle theory

    Homework Statement two alternating currents I1 and I2 flow into a circuit node,the output current I is given by adding I1 and I 2. find I and t, when I1 and I2 are as follows Homework Equations I1=5sin(50t +Pi/3) I2=6cos50t The Attempt at a Solution...
  32. P

    Explaining the Basics of Phase AC Current

    Is there anyone can describle phase ac?
  33. D

    Find the maximum AC current flowing through the generator.

    QUESTION 10*** A generator with output voltage ε(t) = εmax cos (ωt) is connected to the primary of a transformer. A resistor is connected to the transformer secondary. The transformer has an iron core with N1 turns on the primary and N2 turns on the secondary. Assume that the transformer is...
  34. W

    AC current & how electocution happens

    Am I understanding this correctly? If a person is touching the hot wire in their house (AC) and they are grounded ... this completes the circuit. In AC electrons move back and forth a few centimeters, 60 times each second (60Hz). Therefore, if electocution happens, it is a lot of charge...
  35. alexmahone

    How Does Frequency Variation Affect RMS Current in an AC Circuit?

    A coil, a capacitor and an AC source of RMS voltage 24 V are connected in series. By varying the frequency of the source, a maximun RMS current of 6 A is observed. If this coil is connected to a battery of emf 12 V and internal resistance 4 \Omega, the current through it will be (a) 2.4 A (b)...
  36. J

    AC Current Source from a function generator

    First of all, i do not know if this is the ideal forum. If not, mods, please move it. Second of all, I know the title is redudant but whatever. Anyway, I am doing some experimental work that requires us to be able to controll the current, but we want to have it be a sine wave. We had been...
  37. D

    AC current measurement question

    Please excuse my rather dim question but I'm very familiar with homebrewing all manner of DC powered circuits but when it comes to AC..I'm in the dark, sorry. I'm building a firing circuit for oilfield perforating. We will have AC (Generator) so I'm using a variac to slowly build-up voltage...
  38. K

    Calculating AC Current for a 0.197 H Inductor with 166 V Peak Voltage

    Homework Statement A circuit contains only 0.197 H inductor. An AC voltage of peak value 166 V and frequency 60.5 Hz is applied to the circuit. When the voltage is 166 V, what is AC current? Answer in units of A. Homework Equations The Attempt at a Solution we know that...
  39. W

    Average Power in an AC current.

    Homework Statement The average power in an Alternating Current (AC) circuit with effective voltage V and effective current, I, is given by which of the following? (Note: effective and RMS are the same) a. 0.5 x VI b. VI c. 2.0 x VI d. 4.0 x VI e. V2I The Attempt...
  40. I

    Harness AC Current for Breadboard w/ LabPro

    Hello All, I am currently in need of rigging an AC CIrcuit within my household in order to run through a breadboard where I can "play with it" and observe it with Vernier LabPro equiptment. My problem is that I only have a power supply at my disposal. Since a house runs on AC current is there...
  41. I

    Boiling water by high frequency AC current

    I've heard that if you pass a high frequency AC (26kHz?) current through water it boils. Does anyone know if there is any truth to this? Has anyone ever done it?
  42. eberg

    Discovering How to Measure AC Current for a 120V Device | Tips and Tricks

    Hi Everyone, I'm new to the forum, this is a great place to dig around and do some reading. My first question is: I want to read the current draw (amps) of a 120V AC device (standard wall plug). I've worked with DC quite a bit but rarely with AC. Can I just probe the plug spades with a...
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