What is Ac circuit: Definition and 199 Discussions

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation is performed by the inverter.
The process is known as rectification, since it "straightens" the direction of current. Physically, rectifiers take a number of forms, including vacuum tube diodes, wet chemical cells, mercury-arc valves, stacks of copper and selenium oxide plates, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motors have been used. Early radio receivers, called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detector".
Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, detectors of radio signals serve as rectifiers. In gas heating systems flame rectification is used to detect presence of a flame.
Depending on the type of alternating current supply and the arrangement of the rectifier circuit, the output voltage may require additional smoothing to produce a uniform steady voltage. Many applications of rectifiers, such as power supplies for radio, television and computer equipment, require a steady constant DC voltage (as would be produced by a battery). In these applications the output of the rectifier is smoothed by an electronic filter, which may be a capacitor, choke, or set of capacitors, chokes and resistors, possibly followed by a voltage regulator to produce a steady voltage.
More complex circuitry that performs the opposite function, that is converting DC to AC, is called an inverter.

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  1. Z

    How to find voltage across capacitor in RLC circuit?

    By Faraday's law $$-V(t)+I(t)R+\frac{q(t)}{C}=-L\dot{I}(t)\tag{1}$$ $$\dot{I}+\frac{R}{L}I+\frac{1}{LC}q=\frac{V(t)}{L}\tag{2}$$ Here we can either form a differential equation in ##q(t)## or we can differentiate and form one in ##I(t)##. These equations are...
  2. T

    Power dissipated over 1 cycle of a AC source-free RLC series circuit?

    I tried to start by assuming that we need to integrate something over 1 period (2pi). Therefore, we need i(t)^2 R integrated over something. From there, I recognized that this is an underdamped model since R/2L < 1/sqrt(LC). I believe that i(t) can be represented by i(t) = e^(-at)[A_1 cos(w_d t)...
  3. S

    Engineering Intro to Power Systems: AC RLC circuit voltage calculations

    ##V_{S} = 120V ## ##f = 60Hz## ##L = 20mH## ##R = 10\Omega ## (a) Assume the capacitance is omitted. What is the resistor voltage? ##X_{L} = j\omega L = j2.4\pi## ##V_{R} = Vs\cdot \frac{R}{R+X_{L}} = 76.5067-j57.6847## ##V_{L} = Vs\cdot \frac{X_{L}}{R+X_{L}} = 43.493+j57.6847## (b) What...
  4. S

    Minimum resistance to prevent overheating in AC circuit

    My calculation: ##400=\left(\frac{9.9}{\sqrt{2}}\right)^2 R## and I got R = 8.2 ohm But the answer key used Io (9.9 A) instead of Irms Why? Thanks
  5. Lotto

    B Why can't we calculate capacitive reactance like u/i?

    When I write ##X_C=\frac ui=\frac{U_\mathrm m \sin \omega t}{I_\mathrm m \sin \left(\omega t+\frac{\pi}{2}\right)}##, it should be ##\frac{U_\mathrm m}{I_\mathrm m}##, but it isn't. Why?
  6. F

    Engineering Use voltage nodal analysis to solve for the current flowing in this AC circuit

    Hi first time using this forum, I have some homework that I am entirely stuck on, can anyone help me with this question? I understand the placement of nodes, and that I need to convert complex numbers, but apart from that I have no idea what direction that I'm supposed to take in this. I don't...
  7. bluesteels

    AC circuit power formula question

    im kinda confused on why can't you just use the formula P=I^2R. Can you just use Vrms or Vamp (not sure which one is it) and the value of R which is 105Ω to solve for I Then just plug it in the formula P=I^2R. But when i did that it the wrong answer so is this formula don't work for AC...
  8. V

    Determining inductive reactance from a 3-phase AC circuit

    I am trying to figure something out, but I am in the first step and just trying to get through my "thought experiment". Let's say I have a 480V 60hz 3 phase supply feeding a circuit that comprises of nothing but the conductors themselves (effectively a shorted power supply). Consider the...
  9. Franklie001

    AC circuit analysis involving resistors and inductors

    Summary:: Hi anyone can explain me how to solve this circuit, finding the current I2 and I1? Really don't know where to start Thanks
  10. D

    Engineering Maximal effect in an AC circuit

    Hello again, I have a solution for the question, but as it is my first time solving these types of exercises I am uncertain if I my solution is correct. The first picture represents the exercise with the circuit and the second is the just some rewrites of the circuit, in swedish. Picture 3 and 4...
  11. M

    Engineering AC Circuit Phasors: Find I1, I2, I3

    Summary:: Hi, I tried attempting this problem in alternating current in order to find out the phasors as complex numbers, and I would be more than grateful if someone could peer review it, and confirm my calculations (Please see below both the Figure and the calculations) Please find attached...
  12. D

    Engineering Active and reactive effect in AC circuit

    Hi, I am once again asking for help regarding a AC circuit problem. This time I need to compute reactive and active effect for z=R2+C3 in the below circuit. I have already computed u(t) from before so that solves half of the problem. I am unsure if I have done the calculations correct, not much...
  13. B

    Induced EMF in a small square loop of wire at center of an AC Circuit

    I used the voltage of the power supply and resistance to solve for the current in the larger circuit (20V/5ohms=4 amps). I am not sure if the equation listed above is the correct one I should be using, but I tried it using the following numbers. For omega, I used 2*pi*frequency. N should...
  14. hquang001

    Which Formula Should I Use for Calculating Power in an AC Circuit?

    Should i use P = V.I or P = Vrms.Irms.cosφ ?
  15. bardia sepehrnia

    Engineering Calculating Power Factor in an AC circuit, given voltage and current

    My attempt at solving this question: I realized my attempt is wrong however I just don't know how to proceed in the first step. How can I calculate the phase shift? and find Voltage and Current in phasor form??If I know that, then I can use power factor formula: pf=Pav/V*I
  16. K

    I AC circuit and non-conservative field

    *Please refer to the attached question file
  17. T

    A different angle of Why do you need a line 2 on an AC circuit?

    Preface to thread: I am darn well aware of the fact that on an AC circuit, there has to be a line 2 after the load to bring current back to the power source. This thread is about WHY does there have to be a line 2 after the load to bring current back to the power source. I hope that I don't...
  18. S

    [AC Circuit] How do we convert from the time domain to the phasor domain?

    In this example, We need to covert e2 & e5 to a form with imaginary number . we will obtain e2=j10 & e5=20 Can anyone explain how we got this?
  19. F

    Boundary conditions for a purely inductive load in an AC circuit

    Hi all, Kirchhoff's equation for this simple circuit is equivalent to \dot I=\frac{V}{L} Where V=V_0 \sin(\omega t). Integrating both sides should give I(t) = -\frac{V_0}{L\omega} \cos(\omega t)+c where c is an arbitrary constant (current). Here, most of the derivations I've found simply drop...
  20. A

    Frequency in an AC circuit given capacitance, voltage, and current

    By combining the formula for the reactance of a capacitor with Ohm's Law for a capacitor, I can solve for angular frequency, and divide by 2π to find frequency. The resulting equation is: f = I/(2π VC) Using the given values, I end up with 5.2 kHz, instead of the correct answer of 5.2 MHz. I...
  21. M

    Engineering AC circuit: Find the current through the inductor & capacitor

    Hi! I wonder if it is correct. Can someone confirm (maybe with a software) ? I(L) = I2 I(C) = I2 - I3 -- Thanks.
  22. M

    Calculating Vo in an AC Circuit Using Superposition Theorem

    This is the circuit: I try with KVL: But the given answer is 6.66L33.67 Volts. So, I'm confused, any suggestions ?
  23. W

    Theoretical question about an electromagnet in an AC circuit

    This may be a stupid question, but here is what I am asking. Using a very simple circuit, say 120v AC water heating element rated at 1000 watts meaning 120v AC hot leg on 1 terminal and a neutral on the other terminal. That would give 8.3 amps of current, meaning the resistance would be 14.4...
  24. F

    Use a MATLAB Workspace to get the unknown values in an AC circuit

    The plot of part b is attached below. I got a warning on part a , I don't know where is my mistake . Please check my work . Part A clc; clear all; %parta f=800; t=0:10e-6:0.005; xc=10^(-6); xl=40e-3; for i=1:(0.005)/(10e-6) w=2*f*pi; zeq=xl*j*w+50; is(i)=2*(1600*t(i)*pi)...
  25. F

    Engineering Draw the magnitude and phase angle of a voltage in this AC circuit

    My solution is attached below. I am not sure if my answer is correct or not , I want to confirm it.
  26. L

    How to introduce a phase shift in an AC circuit

    Hello, I am trying to think of a way to introduce a phase shift in an ac circuit. For example, sin(omega*t+theta) to change theta. How can I go about doing this? I do not think introducing a cap or inductor would work, even though it shifts the voltage from the current graphs (phasors). A...
  27. M

    Engineering Nodal analysis of an AC circuit

    Homework Statement Hi I have this question as part of my assignment but cannot get my head around part b, I have worked out part a with an answer of -9.2+17.3i amps which from a previous thread I know is correct, but can't understand why the equations given in the previous thread are different...
  28. 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...
  29. archaic

    AC Circuit and Thevenin's theorem

    Homework Statement I'm asked to find the thevenin equivalent circuit, the load being ##R_1## ##e(t)=E_0\cos{(\omega t)}## ##R_1=1k\Omega \ R_2=R_3=1k\Omega## ##C=220nF \ f = 250Hz \ E_0=10V## Homework EquationsThe Attempt at a Solution ##Z_{th} = Z_{R_2}//(Z_c+Z_{R_3}) =...
  30. P

    Why don't voltages add up numerically in an LCR AC circuit?

    The attempt at a solution (Assuming the components are in series of this order: resistor, inductor, capacitor So I know that the phases are not in sync, that as the voltage oscillates the voltage across each component in the circuit is different. At the peak voltage aka peak current the voltage...
  31. A

    AC circuit, voltage and frequency problem

    Homework Statement According to Equation 20.7, an ac voltage V is given as a function of time t by V = Vo sin 2ft, where Vo is the peak voltage and f is the frequency (in hertz). For a frequency of 64.7 Hz, what is the smallest value of the time at which the voltage equals one-half of the...
  32. Zam0la

    If the AC EMF is 0 at t=0, then how does current pass through a capacitor?

    Hi, I have a problem understanding the ac capacitive circuit, where Vc = Vm * sin(ωt), and, current leads the voltage, so at t = 0, v = 0 which means no emf, no pushing energy for the electrons, I think, then how current is max? what is the energy source that supplied the electrons with the...
  33. OldWorldBlues

    Easy way to calculate losses for re-purposing a transformer?

    Hi everyone! This is my first thread :) I've been working a bit with AC and radio, and would like to make a simple(-ish) circuit in which a 1-volt peak audio signal is stepped up to around 5 volts with a transformer, and is fed into a crystal oscillator to make a crude-but-effective AM...
  34. Valour549

    AC Circuit Analysis- Find Impedance

    Homework Statement 2. The attempt at a solution Am I doing something wrong? I know it's just voltage division with AC phasors and we have to equate the real parts and imaginary parts to find the unknown, but I feel like the question shouldn't be this hard.
  35. D

    Engineering Calculating the effective value and frequency of AC Circuit

    Homework Statement For AC Circuit shown in the picture, ##C=60nF##, ##L=100uH##, ##X_3=-100Ω##, ##Z_2=50Ω## and ##Φ_2=\frac {\pi}{6}##. When the switch is closed the ammeter shows a current ##I_1=0.6A## and the voltmeter shows ##U_l=60V##. The measuring instruments mentioned are ideal...
  36. J

    AC circuit Multiple choice question

    Homework Statement More than one options may be correct . Homework Equations Inductive reactance =ωL Capacitive reactance = 1/ωC The Attempt at a Solution On increasing the frequency , inductive reactance increases whereas capacitive reactance decreases . Thus , option a) is correct ...
  37. T

    Retired Railroader Explains Easiest AC Circuit Theory

    I am retired from a major railroad co. where I worked on electronic weighing equipment. I have an associate of applied science degree from a local university. I have a basic understanding of dc and ac electricity but the explanation I recently read on this forum was the easiest to understand...
  38. I

    Calculating capacitance from an AC circuit

    This question is from my physics book and neither I nor my teacher can find the mistake in my method. (The original question is not in English so I'll do my best translating it) > When a coffee maker is connected to the wall (230 V, 50 Hz) its power consumption is 180 W. The power consumption...
  39. J

    Engineering AC Circuit Power/impedance question

    Homework Statement For the circuit given in FIGURE 1 the power factor is 0.72 lagging and the power dissipated is 375 W. Determine the: (i) apparent power(ii) reactive power (iii) the magnitude of the current flowing in the circuit(iv) the value of the impedance Z and state whether...
  40. J

    Engineering AC Circuit Voltage Waveform Analysis

    Homework Statement An A.C. voltage, V, comprises a fundamental voltage of 100V rms at a frequency of 120 Hz, a 3rd harmonic which is 20% of the fundamental, a 5th harmonic which is 10% of the fundamental and at a phase angle of 1.2 radians lagging. (i) Write down an expression for the...
  41. A

    How can I relate the electric field to potential in a parallel plate capacitor?

    I want to calculate Electric field inside and outside a capacitor(two parallel conductor plates and in between a dielectric) which is fed by an AC voltage source. My problem is I do not know how can I relate the electric field to the potential in a capacitor. I got confused about the derivative...
  42. R

    Calculate the RMS current of an ac circuit

    Homework Statement : [/B] calculate rms value of current i= 3+ 4 sin(ωt+π/3)Homework Equations : [/B] Irms2=(∫0T [I(t)]2dt)/TThe Attempt at a Solution: I tried to integrate but I'm getting a T term.
  43. peroAlex

    Computation of Thevenin Equivalent

    Hello! Recently I was going through some old exams and upon encountering this problem (which seemed pretty easy) I got stuck. Exams at my university are composed of individual tasks, each having three subquestions with four plausible answers respectively. Solution sheet gives results only, so...
  44. Tom Moynihab

    Engineering Voltage and phase between two branches of ac circuit

    【Mod Note: moved from technical forum, so homework template is missing】 In a parallel circuit, one branch contains two equal resistors of resistance ##R_1## connected in series. The other branch contains a resistor of resistance ##R_1## in series with an inductor of variable inductance ##L##...
  45. A

    What is the approach to solving this AC circuit voltage problem using phasors?

    Homework Statement the problem is given in the attachment Homework Equations basic knowledge of ac circuits and phasor diagrams The Attempt at a Solution for point A , i calculated the potential easily. and for point B , i calculated the potential using phasor relationship .. now after doing...
  46. Deniz

    Complex Power Homework: Is My Solution Right?

    Homework Statement y = 27 Homework Equations The Attempt at a Solution - I calculated the total impedance. - Divide it with the voltage to get the current. - Then I use the load impedance to find the voltage load. - And I calculated the complex power for the load. I am not comfortable...
  47. Marcus95

    Width of Resonance in RLC-circuit

    Homework Statement In an undriven RLC-circuit, the characteristic time of the capacitor, ie the time taken for the amplitude of the capacitor voltage ## V_c ## to drop by a factor e, is ## T = 2L/R ##. We now have a RLC-circuit which is driven by a AC voltage of variable frequency ## \omega ##...
  48. I

    RLC Black box at different frequencies

    Supposed there is a black box connect to an AC circuit. Inside the black box, there are either a resistor connected with a capacitor or a resistor connected with a inductor. They can be connected either in series or in parallel. The total impedance and phase shift of the black box at 2 different...
  49. G

    Engineering AC circuit with a switch -- analysis

    Homework Statement Given the circuit of sinusoidal current (attachment1) with given data: \underline{Z_3}=200(3-j4)\Omega,\underline{Z_4}=100(3+j20)\Omega,\underline{Z_5}=100(3+j4)\Omega,\underline{Z}=100(2+j5)\Omega,\underline{I_{g2}}=-10(2-j)mA. After the switch is closed, the increment of...