What is Ac circuits: Definition and 75 Discussions

In circuit complexity, AC is a complexity class hierarchy. Each class, ACi, consists of the languages recognized by Boolean circuits with depth





{\displaystyle O(\log ^{i}n)}
and a polynomial number of unlimited fan-in AND and OR gates.
The name "AC" was chosen by analogy to NC, with the "A" in the name standing for "alternating" and referring both to the alternation between the AND and OR gates in the circuits and to alternating Turing machines.The smallest AC class is AC0, consisting of constant-depth unlimited fan-in circuits.
The total hierarchy of AC classes is defined as







{\displaystyle {\mbox{AC}}=\bigcup _{i\geq 0}{\mbox{AC}}^{i}}

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  1. M

    Engineering Applying Thevenin's theorem to AC circuits

    So I've seen other threads on here with the same problem from a few years ago, and I'm just not getting the same answers. However, I followed along with a similar problem in the textbook and used all the same methods, so can't understand where I've gone wrong, or if I even am wrong. Also not...
  2. Secre

    Engineering How to deal with dc source on ac circuits?

    We are tasked to solve for the steady state voltage v using superposition theorem. I start with solving with voltage source using mesh analysis and got the current flowing through the 3 ohms resistor and get the first value of the voltage which is 3.2cos(6t+126.87). Now my problem is I am...
  3. wcjy

    Circuits - AC circuits / phasor

    Hi, my school has no answer key provided. and would like to check if this is correct. Thanks!
  4. P

    How does smoothing an AC voltage with a capacitor work?

    Specifically for part (i) and (ii), I get the rough idea that when the voltage of the AC source is decreasing, the capacitor can discharge to "cushion" the drop in voltage. However, I have some questions about when this occurs. 1. There is an assumption that the capacitor will be charged to...
  5. P

    Olympiad AC Circuits Problem

    The problem is shown below: (I am only asking about part b) ^Above is the problem. Below is the solution to part b. They have claimed that we can set potential at C = D = u(t), and A=B=0. Why is this claim true? What I realize: By applying Kirchoff's across ACDB, Voltage across C1 = Voltage...
  6. HansBu

    Solving Diff. Eqn & Designing Circuits: An Understanding

    where: 𝑣𝑖𝑛(𝑡)=0.3𝑐𝑜𝑠100𝑡 I have read all over the internet that this differential equation can be solved by isolating the term with the highest degree on one side of the equation. After doing so, I integrated it. However after integrating, I don't know that the next step is. Can anyone help me...
  7. C

    I How do I calculate the expected Gain?

    I am doing an experiment in electronics with AC RLC circuits, But there are a few things about what I need to do that I don't understand. First: While I know in the circuit diagram we include the internal resistance of the Inductor in series, but I don't know why we include it in series rather...
  8. Kevin J

    B Are these AC circuits different? And does grounding change the voltage?

    The first picture is a regular ac circuit, where the voltage alternates between 240V/0V in one of the wire. The second picture is a live/hot & neutral ac circuit. Are these 2 different type of circuits? And if I connect the top circuit to the ground which makes it neutral (just like the pic in...
  9. D

    Loss of energy in DC and loss reduction in AC circuits

    Homework Statement similarities and differences of AC and DC current in simple circuits. Outline using diagrams and a clear desciption the loss of energy in DC circuits and power loss reduction of AC when transmitted. Homework Equations N/A The Attempt at a Solution DC loses energy over long...
  10. harambe

    But is it the same for AC circuits?

    Homework Statement For a series LCR circuit,the voltage across the resistance,capacitance and inductance is 10V each.If the capacitance is short circuited,the voltage across the inductance will be (a)10V (b)10/√2V (c) 10/3v (d)20V Homework Equations Potential difference across...
  11. P

    Resistance and capacitance in LCR circuits

    Homework Statement The output voltage, V_(out) (t) ‡ q(t) /C, effectively measures the charge on the capacitor as a function of time, where q(t) is an exponentially damped simple-harmonic oscillation: a) Given that L = 0.05 mH, the square-wave frequency is 25kHz, and the ringing decays to 40%...
  12. J

    Engineering Troubleshooting AC Circuits: Tips and Solutions for Common Issues

    Hey guys, I'm having trouble solving this particular circuit Thanks in advance. <Moved to Homework, no template completed>
  13. C

    Understanding RLC AC circuits

    I'm having trouble understanding RLC circuits. If I have a resistor, capacitor, and inductor connected in series and I'm GIVEN the current through the resistor, How do I find the currents through each component? Is it the current that was given for the resistor (since they're in series), or do I...
  14. Peter Andrews

    Finding displacement current in an AC capacitor circuit

    Homework Statement A capacitor is made of two parallel plates of area A, separation d. It is being charged by an AC source. Show that the displacement current inside the capacitor is the same as the conduction current. Homework Equations Idisp = ε(dΦE/dt) Q = CV C = Aε/d Xc = 1/(2πƒC) Q(t)...
  15. Y

    Do we get 2x the frequency when doing P=VI for AC Circuits?

    I know that when you get a current from a voltage (like calculating current through resistor), the current and voltage equations have the same frequency. Does this still hold for power P = VI ? So assume V in Euler form, V(t) = Vcos(wt+theta) + jVsin(wt+theta) = V*ej(wt+theta) and in Phasor...
  16. Calpalned

    Engineering Application to AC circuits

    Homework Statement Prove that current ##I = I_0\sin{\omega t}## can be rewritten as ##I = I_0 e^{i\omega t}## Homework Equations Euler's formula ##re^{i\theta} = r(\cos{\theta}+i\sin{\theta})## The Attempt at a Solution If ##r = I_0## and ##\theta = \omega t ## then ##re^{i\theta} =...
  17. Calpalned

    Application to AC circuits.

    Homework Statement Homework Equations ##a + bi## complex notation Rules of resistors given in part b b = imaginary part The Attempt at a Solution For part (a) how do I rewrite I(t) as a + bi? For part (b) I need a formula that equates Z to R. For part (c) do I simply write b (from part...
  18. Y

    Engineering Electrical Engineering - AC Circuits Phasors

    Homework Statement Please see attached image 1 and image 2 Homework EquationsThe Attempt at a Solution Alright so I believe I solved part a correctly. It was very easy. (A) 5 * phasor of 30 degrees However it's been a while since I took circuits 1, so I'm struggling a bit with part (b)...
  19. R

    Engineering Calculating values of impedance in a series/parallel circuit

    Homework Statement Hello everyone, I have recently come under some stress from not being able to get these answers correct. I need to calculate these values: Zeq IT XL2 XL1 VR1 VR2 VL1 VL2 For this series circuit: And these values: Zeq IT XL2 XL1 IR1 IR2 IL1 IL2 For this parallel circuit...
  20. J

    RMS in AC Circuits: Why Use Square for Mean Values?

    Why do we use the square of the graph as opposed to the absolute value of the graph to find the mean values?
  21. 2

    Engineering Question about dc to ac circuits in solar panels?

    Homework Statement It can be shown that a square wave can be represented by a sum of sine waves as given by the formula below v = v0sinωot + v1sinω1t + v2sinω2t + v3sinω3t +... Solar cells have an output that is dc. The pd across a cell depends on the incident radiation and the efficiency of...
  22. H

    Engineering Delta and star transformation of AC circuits

    Homework Statement For the balanced three-phase loads shown in FIGURE 3, ZY = (15 + j15) Ω and ZΔ = (45 + j45) Ω. Determine: Uploaded file C1.png (a) the equivalent single Δ-connected load, (b) the equivalent single Y-connected load obtained from the Δ-Y transformation of (a) above, (c) the...
  23. 159753x

    Calculating voltage division for an AC circuit?

    Homework Statement A series RL circuit is connected to a 110-V ac source. If the voltage across the resistor is 85 V, find the voltage across the inductor. Homework Equations V = IR The Attempt at a Solution How does one go about solving this? My intuition tells me that KVL must be...
  24. G

    Engineering AC Circuit (RL) Homework: Finding the Series R-L Equivalent for Two Loads

    Homework Statement In the circuit shown in Figure Q2(b), two loads A and B are connected to the source. The cable connecting the power supply to the load is modeled as series R and L of values R = 0.1Ω, L = 0.1 mH as shown in the figure. The loads have the following specifications...
  25. D

    AC circuits -- Why we introduce the J operator in analyzing them

    I am just wondering why or how we introduce the J operator in analyzing ac circuits. I want more of a proof for this.
  26. chakr

    Measuring Power Factor in AC Circuits

    How can one measure power factor in AC circuit? http://www.cnktechlabs.com/index_files/cnkdevelopmentkit.htm [Broken]
  27. M

    How do AC circuits function?

    Hey, I don't if this is the right place to ask ( it is not a homework question but just a curious one about what i read in my textbook).. How can AC circuits even work? If the drift speed of an electron in a normal household wiring is something in the micro m/s and it reverse every 1/120 per...
  28. M

    Engineering Solving AC Circuits: Vin, R, L & C Values

    Homework Statement The AC circuit is the following: Vin = 10√2*sinωt V R = 5 Ω L = 5 mH C = 100 µF a) what is Vout when the frequency (f) is 100hZ Homework Equations The Attempt at a Solution After two weeks of spring break in addition to Easter holiday, I'm well...
  29. V

    Thevenin's Theorem: AC Circuits with Different Frequencies

    My textbook has this excerpt: I am not sure why it refers to Example 10.6 as that is unrelated. I don't understand to be honest. How can you calculate the Thevenin equivalent at different frequencies? Let us say that you have two voltage source: v1(t)=10cos(5t) and v2(t)=10cos(2t). So how...
  30. N

    AC circuits - Complex vs Ordinary notation

    When doing calculations on AC circuits, what is in your opinion the best notation? Here they mostly use complex notation. For example: V(t) = Vmaxeiωt. In US textbooks (at the non-EE level), they only use ordinary notation. Example: V(t) = Vmaxcos(ωt). I have a feeling that complex notation is...
  31. P

    AC Circuits - peak to peak voltage

    Let's say you have a sine wave V=2sin(2t) V. For this peak to peak voltage is 4V. Then let's say that everything below V=0 is cut off. Is the peak to peak value for this just from 0 to 2V? Making Vpp=2V?
  32. W

    AC Circuits Terminology: Phase shift vs Phase Angle

    We talked about AC circuits and phase shifts were discussed. Voltage changes "lag behind" current changes so that's how we get phase shifts. It's like a sinusoid so fine. Then we talked about impedance. There's a real and "imaginary" component to impedance, graphed on x-axis and y-axis...
  33. A

    KVL in AC Circuits: Exploring Accuracy

    Hello, Why do we use KVL in Ac circuits ?! or to be more specific is it accurate to use it in Ac circuit , just the same accuracy as using it in Dc ?! Doesn't the current that pass through the circuit itself make it's own variable magnetic field , which crosses the loop of the circle ...
  34. T

    Time constant in RC AC and RL AC Circuits?

    Homework Statement I know that in a RC DC circuit the time constant is R*C. But what about a RC AC circuit, is it the same time constant? Same goes with RL AC circuit, is the time constant R/L? Thanks!
  35. S

    Looking for problems with AC circuits

    Hi! I was wondering if there are any guides with problems and exercises relating AC circuits (capacitors and inductors), circuits with phasors and real, reactive, and apparent powers. I do not need the answers, I just need a selection of exercises to study from there.
  36. Y

    AC Circuits question verification

    Hi there, in this youtube tutorial about AC circuits http://www.youtube.com/watch?v=JiLdrAHBBRc&feature=plcp at about 4:08 It's supposed to be z=√(R^2+(XL-Xc)^2)) but in the example she does Xc-XL, is there a reason for this or is it a mistake in her working??
  37. T

    AC Circuits: Voltage Changes and Neutral Becoming Live?

    I was just reviewing AC circuits and the diagram shows that the voltage changes in AC, it goes up and down and on the diagram is shows the current goes one way then the other. But in AC, does the neutral become live? I thought the red was always the live wire! but according to the diagram...
  38. P

    Energy in AC Circuits: No Frequency Involved

    Given that: E = hν where E = energy of a photon h = Planck's constant = 6.626 x 10-34 J·s ν = frequency Why is it that the energy (electromagnetic waves) in AC electrical circuits does not include frequency as part of the formula? eg. \begin{array}{l} P =...
  39. S

    Nodal Analysis and Power Balance in AC Circuits

    I'm working on an ac circuit, and we were told to use nodal analysis. Furthermore, we are asked to show a power balance between the sources and the power dissipated in the resistors, along with a reactive power balance between the sources and the inductors and capacitors. I have this formula...
  40. C

    Engineering AC Circuits confirmation

    For the circuit given in the power factor is 0.72 lagging and the power dissipated is 375 W. Determine the: (1) apparent power (2) reactive power (3) the magnitude of the current flowing in the circuit (4) the value of the impedance Z and state whether circuit is inductive or...
  41. J

    AC Circuits values problem

    Homework Statement A complex AC voltage is given by the equation v = 3e^j450t : Note the use of bold v to represent the complex voltage. For this voltage waveform, what are the values of -volltage amplitide -frequency -instantaneous voltage -graph it in a argand diagram at t=pi/1800 Homework...
  42. E

    Hey there,I've been learning about AC circuits recently and while

    Hey there, I've been learning about AC circuits recently and while considering and LCR circuit it occurred to me; it's possible for the voltage drop across a capacitor/inductor/both to be greater than the voltage source itself however I can't think of the reason for this, any hints or reasons...
  43. H

    Inductors & AC Circuits (Homework) (RL Circuit)

    Homework Statement What is the inductance in a series RL circuit in which R = 7.0 kΩ if the current increases to one half of its final value in 26 µs? Homework Equations am i correct in assuming that i should be using the time constant equation: Tau=L/R The Attempt at a Solution...
  44. W

    AC Circuits / Alternating Current

    Hi, PF :) I was self-studying AC circuits, and my main goal right now is to understand impedance. However, before that, I was wondering how one would derive the formulas for alternating voltage (and current), namely http://upload.wikimedia.org/math/5/a/0/5a0ecaa1432c6cdce653a943b4962a21.png...
  45. K

    RMS voltage, phase angle, AC circuits

    Homework Statement An AC power supply with a peak volatge output of 200 volts, operating at 60 Hz, is connected to a 53 microFurad capacitor A) what is the difference in phase angle between the applied voltage and the current B) what is the rms current in the circuit C) what is...
  46. C

    Place to learn circuits 2? ac circuits class

    im taking circuit theory 2, which is all about ac circuits, but don't have enough money for a book need a place to learn about how to calculate lead and lag based on the inductance and capacitance, nortons and thevinans and all that stuff but in the context of sinusoidal currents and voltages
  47. R

    Help on AC Circuits: Power Factor = 1.0

    Hey guys I just need some help on something The question is: A motor attached to a 120 V/60 Hz power line draws an 8.50 A current. Its average energy dissipation is 800 W. I got the first 3 parts of this question correct... 1. What is the power factor ans = .784 2. What...
  48. K

    AC circuits, Inductance and phase shift.

    Homework Statement An electric motor draws a 1A (rms) from the 230V (rms) mains. and is found to shift the phase of the 50Hz alternating current by 30% of the period. What is the self inductance of the coils in the motor? Homework Equations The Attempt at a Solution i've started...
  49. M

    AC circuits with complex numbers

    Hello, My prof showed a way of dealing with difficult circuits using complex numbers. But I have no idea what he was on about, and can't find that method in any book. Does someone know what I'm talking about, and can someone point me in the way of some materials for this? Thanks!