What is Rc circuit: Definition and 394 Discussions

A resistor–capacitor circuit (RC circuit), or RC filter or RC network, is an electric circuit composed of resistors and capacitors. It may be driven by a voltage or current source and these will produce different responses. A first order RC circuit is composed of one resistor and one capacitor and is the simplest type of RC circuit.
RC circuits can be used to filter a signal by blocking certain frequencies and passing others. The two most common RC filters are the high-pass filters and low-pass filters; band-pass filters and band-stop filters usually require RLC filters, though crude ones can be made with RC filters.

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  1. T

    How to Solve an Increasing RC Circuit with Changing Resistance and Capacitance?

    Hey, Actually I am working on my research project and facing a problem on solving a simple series RC circuit. But the problem is the Resistance and capacitance of the circuit is increasing with the time, and I am working on finding the value of R and C at the steady state as well as the time...
  2. I

    Engineering Determining current in a transient RC circuit

    Homework Statement For the below circuit, the switch was open for a long time. Find the current Ia(t) for t>0. All capacitors are initially uncharged.Homework Equations Complete response of a capacitor: v(t) = Voc + (v(0) - Voc)e^(-t/τ) Combining parallel capacitors: summation Current through a...
  3. D

    Engineering Signal flow graph, describing a RC circuit?

    Signal flow graph, describing a RC circuit? Hi, guys. This is my first post on this forum! I'm trying to understand this example in my textbook. The current and voltage equations are: where G=1/R, Z(s)=1/Cs, and I1(s)=I1 Then the text says the following signal flow graph can be obtained: And...
  4. M

    RC Circuit: Effects of Increasing R on E and V

    Supposing we have an RC circuit (see figure) As we increase R, what will happen to the visualized signal of E and V(capacitor) and V(resistor)? And a general question about measuring the (Tao) [the one that equals to RC] BUT FROM THE OSCILLOSCOPE.. They mentioned it is the time for...
  5. M

    Engineering RC circuit Transfer Function/bode plot

    Homework Statement I have for the attached circuit measured the amplitude and phase response, but the question I have to answer is too theoretically, derive, similar results and then compare the two methods. It is suggested to figure out the transfer function and plot the magnitude and phase...
  6. E

    Designing an Efficient RC Circuit for Linear Ramp Control

    Hello! I'm trying to activate a solenoid with a linear ramp in voltage of 0 - 24VDC in 2 seconds. An RC series circuit helps achieve soft start but in an exponential way (with 63% of supply voltage in 1 time constant). Can I use a single circuit for charging and discharging? (linear ramp down...
  7. L

    Engineering Reducing noise in strain gauge using an RC circuit

    Vibrations of a motor (40Hz) cause noise on the signal of a strain gauge that monitors load on a cantilever that measures periodic load changes at the rate of 1/minute. Design a filter that reduces the signal caused by the vibrations by 90%. I thought about a low pass filter that has a cut...
  8. J

    Why Does the Sign of dq/dt Change in RC Circuit Equations?

    I can't figure out the differential equation made in RC circuits During charging E = iR + q/C ...I understand this During discharging my book says that since E = 0 , iR + q/C = 0 and by using i = dq/dt it solves the equation But using kirchhoffs law i end up with the equation q/C - iR = 0...
  9. L

    Can the Voltage in an RC Circuit be Found by Examining a Picture?

    I have a circuit I need to find a voltage on. Is there a way to figure it out on the provided picture in here? Thanks
  10. D

    RC circuit and Laplace transforms

    Hi everyone, I know this should be obvious, but there's something I am just NOT getting. Imagine a simple series RC circuit with a DC source as shown in the attachment. As can be seen from the picture, I have solved the differential equation in capacitor current in the time domain. In...
  11. QuarkCharmer

    Calculating Resistance in an RC Circuit: A Time Constant Conundrum

    Homework Statement A 5 micro farad capacitor is in series with a resistor, a switch, and a 12VDC ideal battery. The switch is closed at t=0s. The time constant of the circuit is 4.0s. Determine the value of the resistance R? Homework Equations The Attempt at a Solution From another...
  12. P

    Solving Parallel RC Circuit: i(t)=t/3 + 1/2 A

    Parallel RC circuit (Updated) I'm having trouble with a seemingly simple circuit. I have a voltage source (not alternating current) that increases exactly with time. In other words, if you graphed voltage as a function of time, the slope would be 1. The voltage equation is v(t)=t. The capacitor...
  13. C

    Discharging capacitor in RC circuit

    In lab, we built a circuit with a 4.7 micro-F capacitor hooked up to a DC source. In parallel to the capacitor was a 10megaOhm resistance voltmeter. We used the voltmeter to find the voltage drop across the resistor and find the RC constant (supposing unknown C). We would turn on the battery...
  14. P

    RC Circuit , Calculate Time Constant

    Homework Statement Given this diagram: Picture mirror: http://i.minus.com/1331507225/3XjEXOAlTaoJBoBuQFoJiQ/itFBvAiitDZQc.png With S1 switch closed and S2 switch left open, I am trying to find the time constant Homework Equations I know τ = RC for a basic circuit, but how...
  15. H

    Calculate current in one resistor in RC circuit

    Homework Statement The capacitor is initially uncharged when the switch is closed for a long time. Calculate the current through R2. Then find the potential difference across R1, R2, and R3Homework Equations V=IR Iin=IoutThe Attempt at a Solution I first set up current going into top node (I1)...
  16. M

    What is the current through Resistor on RC circuit

    Homework Statement The diagram below depicts an RC-circuit where C = 1.70 μF, R1 = 18.0 Ω, R2 = 10.0 Ω, and V0 = 2.0 V. a.) What is the current through R1 immediately after the switch S is closed? b.) What is the current through R2 after the switch S has been closed for a very long time...
  17. J

    Multiple capacitor RC circuit

    Homework Statement The circuit used in this problem is attached as an image. I made this in gEDA (the circuit is from the homework problem, I just didn't feel like using a scanner to get the image) The 2-microfarad capacitor shown in the circuit attached is fully charged by closing switch...
  18. K

    Solving 2 Loop RC Circuit: Find I1(0)

    Homework Statement A circuit is constructed with four resistors, one capacitor, one battery and a switch as shown. The values for the resistors are: R1 = R2 = 49 Ω, R3 = 64 Ω and R4 = 64 Ω. The capacitance is C = 88 μF and the battery voltage is V = 24 V. The switch has been open for a...
  19. L

    Engineering Solving RC Circuit Voltage: Find Vn

    Homework Statement Find Vn in the attached ckt. Homework Equations The Attempt at a Solution C12 & C2G act as capacitive voltage dividers. But I don't know how to account for R in parallel with C2G.
  20. P

    Calculating Voltage Across a Capacitor in a RC Circuit with Two Resistors

    Homework Statement Given a circuit with two resistors, R and r, and a capacitor of C, and EMF of V0 as shown in the diagram, find the voltage across the capacitor during charging. Prove that this voltage, V is given by V = V0 (r/(R+r)) (1-e-((R+r)t)/(RrC)) Homework Equations N.A...
  21. P

    RC circuit switching at t=0 from A to B

    For the attached rc circuit, at time 0, the switch switches from A to B, how to figure out the voltage wave form at B? When switch switches from A to B, charge has to redistribute between capacitors, but as the voltage across capacitor C2 can't change instantaneously initially there is a...
  22. S

    Engineering First order responce; RC circuit

    Homework Statement Assume there is a voltage source in series with a resistor and a capacitor. Thus, V_S=i(t)R+v_C(t)=CR\frac{dv_C}{dt}+v_C\rightarrow{}dt/(RC)=dv_C/(V_S-v_C) From this point I understand that one has to apply a negative sign to both sides before integrating, but why is it...
  23. C

    Is the Current Zero When a Capacitor is Fully Charged?

    I attached the problem. Is the answer they have for part b wrong? shouldn't the current be 0?
  24. S

    Engineering Understanding RC Circuit Behavior in Excel: Exploring Energy and Current Changes

    Homework Statement Homework Equations v(t) = v0*e^(-t/RC) i(t) = C*(dv/dt) E = .5*C*V^2 P=v*i The Attempt at a Solution I'm having trouble with part e. As far as I can tell, all of my equations are correct, but the total energy delivered is notably less than the initial energy; I was hoping...
  25. W

    RC constant of capacitor in RC circuit as a filter

    We know that for RC circuit as filter or in multiplier we use capacitors having larger RC constant than the period of input signal.but I am confused here: As long as i know the charging and discharging period of a capacitor are equal wether it is fully charged or not...(tell me i am right or...
  26. I

    Engineering Calculating steady-state values in series RC circuit

    Homework Statement Calculate the steady state values of the current, voltages V1 and V2 (defined by a period of time greater than five time constants). (Circuit in ASCII below). + V1 - _________Res (1.2 kΩ)___________ | I => |...
  27. T

    Finding R in a RC circuit given battery, capacitance, and time.

    Homework Statement A 10.0 uF capacitor is charged by a 10-V battery through a resistance R. The capacitor reaches a potential difference of 4.00-V in a time interval of 3.00 s after charging begins. Find R. Homework Equations C = Q/ΔV q = εC(1-e(-t/RC) The Attempt at a Solution...
  28. S

    Three capacitors RC circuit questions

    Homework Statement Three resistors, three capacitors, a battery and two switches are connected in the circuit shown below. The values of all circuit elements are given in the figure. Originally, the switches S1 and S2 are open (as shown) and all of the capacitors are uncharged. At time t =...
  29. C

    Parallel RC circuit with realistic battery

    Here's the problem: Consider the circuit in which a battery with internal resistance r can be connected via a switch to a resistor and capacitor in parallel. Suppose that the capacitor is initially uncharged and then at time t = 0 the switch is closed. After the switch is closed a...
  30. D

    Conceptual RC Circuit questions

    Homework Statement After a long time after the switch is closed. 1) Rank the current of each component. 2) What is the voltage across each component? Homework Equations The Attempt at a Solution 1) The current across B is the same as the capacitor C because the capacitor is...
  31. C

    Behaviour of a RC circuit charging

    Homework Statement A circuit is powered by a 10 V power supply and has a resistor of 500 ohms in series with a capacitor. After 4 seconds, the value of ln(1-(Vc/Vo)) is -2, where Vc is the voltage in the capacitor at a given time and Vo is 10 V. 1) Find the capacitance. 2) Find how long...
  32. I

    Another RC circuit problem, don't understand why my answer is wrong

    Homework Statement In the figure below, R1 = 13.0 kΩ, R2 = 18.0 kΩ, C = 0.600 µF, and the ideal battery has emf = 20.0 V. First, the switch is closed a long time so that the steady state is reached. Then the switch is opened at time t = 0. What is the current in resistor 2 at t = 4.00 ms...
  33. M

    Engineering Thévenin resistance when branch is 0V (RC circuit)

    Homework Statement Prior to t=0, switch is in position A (for long time). Afterward, switch is in position B. We need to derive the equation for vc. Homework Equations v(t)=v(\infty)+[v(0)-v(\infty)]e^\frac{-t}{\tau} \tau=RC The Attempt at a Solution at t=0...
  34. B

    How Long Does It Take for a Capacitor to Reach 80% Charge in an RC Circuit?

    Homework Statement A 4.1e-6 capacitor is connected in series with a 36V battery and a 851 ohlms resistor. At t= 0 the capacitor is uncharged. At what time will the capacitor have 80% of its maximum charge? Homework Equations I = V/R Q = CV I = Q/t The Attempt at a Solution I...
  35. D

    Engineering RC Circuit Transient Response Analysis

    Homework Statement In the circuit shown below the switch has been opened for a very long time and closes at t = 0. Calculate the output voltage VO at: 1: t = 0−; 2: t = 0+; 3: t = t1 = 24 µs; 4: t → ∞. In the circuit shown below the switch has been closed for a very long time and...
  36. K

    Find Complex Outputs of Series RC Circuit

    Homework Statement I need to know the cmoplex current out, the complex voltage out, phase shift of Voltage out relative to the voltage source, and if the filter is high/low pass with the cut off frequency. The circuit is series going 24V AC source at 1000HZ 0deg, to a 47 ohm resistor, to...
  37. B

    Engineering How to calculate time constant in RC circuit

    Hello. Homework Statement Calculate the time response, Vc(t), of the circuit shown in the attached image. Not use Laplace transforms. Homework Equations I know that tau = RC in a typical RC circuit. In general, Vc(t) = {V0 - Vf}*exp(-t/tau) + Vf, where V0 is initial voltage and Vf is final...
  38. C

    2-Capacitor, 2-Resistor Parallel RC Circuit with Switch

    Homework Statement For the attached circuit (which I've drawn rather poorly in GIMP), I need to figure out the charge on each capacitor when the switch has (a) been closed for a long time and (b) been open for a long time. Homework Equations Loop and Junction rules, \DeltaV=IR...
  39. J

    A little different RC circuit problem Help

    Homework Statement First off, thanks for taking a look at my problem guys. I have been given this question as extra credit for a calc-physics II class and at the moment am struggling with pulling the pieces together. At first glance I didn't have to much trouble with it but when I go back to...
  40. 0

    RC Circuit capacitors Question

    Homework Statement All capacitors of the open circuit shown below are discharged when, at time t=0, the switch S1 is closed. At some point later, at time t = t1, the switch S2 is also closed. What is the charge Q2(t2) on the capacitor C2 at time t = t2 > t1...
  41. T

    Calculating Charge and Voltage in an RC Circuit with a Closed Switch

    Homework Statement Switch S has been closed for a long time, and the electric circuit shown in the figure below carries a constant current. Take C1 = 3.00 µF, C2 = 6.00 µF, R1 = 4.00 k, and R2 = 7.00 k. The power delivered to R2 is 2.60 W. Homework Equations (a) Find the charge on...
  42. N

    Time Constant for RC Circuit

    Homework Statement What is the time constant of the circuit shown in the figure? Each resistor has resistance R, and each capacitor has capacitance C. Internal resistance of the battery is negligible. See the attached figure. Homework Equations tau=RC The Attempt at a...
  43. M

    Rc circuit multiple choice don't understand why this is the correct answer

    Homework Statement http://physics.ku.edu.kw/LectureNotes/TheoryCourses/PHYS102/ExamPapers/y0910-2-md2.pdf page 6 number 5 Homework Equations The Attempt at a Solution I don't understand how they got the answers ? i applied the loop and junction rule but they only give me more...
  44. H

    RC Circuit resistance value

    Homework Statement A simple RC Circuit consisting of a 100.0 V-battery in series with a 10.0- uF capacitor and a resistor. Initially, the switch is open and the capacitor is uncharged. Two seconds after the switch is closed, the voltage across the resistor is 37V. Determine the numerical...
  45. D

    Understanding RC Circuit Formulas

    Homework Statement I'm doing a physics lab and have a question about RC circuits. I'm given four formulas: 1a) dQ/dt = -Q/RC 1b) Q = (Qo)e^(-t/RC) 1c) E - RI - Q/C = 0 ---> R(dQ/dt) + Q/C - E = 0 1d) Q(t) = CE[1 - e^(-t/RC)] I am told that 1b is the solution to 1a and 1d is the...
  46. O

    Engineering When is a RC circuit predominantly capacitive or resistive?

    I have a graph of |Z| (magnitude of impedance) vs Frequency, and θºz vs Frequency. These two graphs are of a circuit with one capacitor in series with resistors. I need to find when the RC circuit is predominantly capacitive, and predominantly resistive, using the graphs which are given.
  47. D

    Step response of a RC circuit asking for i(t)

    Homework Statement In attachment Homework Equations i don't understand why it would be asking for the current going through the capcitor, in a dc circuit it should be an open circuit but there will be a voltage over it... after searching through lecture notes and textbook can't find...
  48. B

    Energy of Capacitor in RC Circuit

    Homework Statement The circuit consists of a battery, switch, resistor, and capacitor connected in a loop in series. When the switch is closed at time t=0, a time-dependent current flows out of the battery and charges the capacitor. The capacitor is fully charged at time t=infinity. Show...
  49. M

    RC Circuit, what does it imply when resistance = capacitive reactance (R=Xc)?

    Homework Statement I am trying to complete a lab about RC circuits. I was told to make a graph of both the high-pass and the low-pass filter (frequency vs. Vin/Vout). Then I was asked this question: "Explain why the two lines on your graph should always cross at the frequency where XC =...
  50. W

    Engineering Understanding RC Circuits: Derivative Equations for Voltage and Current

    Hello, I have a question about RC circuit. Given this circuit ---R2--- ---- R1---C1--| |---- ----C2-- which is a resistor followed by a capacitor followed by a resistor in parallel with a capacitor. I have trouble finding the...
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