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. terryds

    Current as a function of time in an RC circuit

    Homework Statement How to determine the current as a function of time that flows in 10 ohm resistor, 100 ohm resistor, and 15 microFarad capacitor? Please help Homework Equations I = V/R I_capacitor = I e^(-t/RC) The Attempt at a Solution I only know the equation V=IR and the capacitor...
  2. terryds

    Solve RC Circuit Problem: R1=10k, R2=15k, C=0.4F, V=20V

    Homework Statement R1 = 10 kohms R2 = 15 kohms C = 0.4F Voltage source = 20 V At first, the switch is closed for a long time so that the capacitor reach its steady-state condition. Then, the switch is opened at t=0. How much does the current flow across R_2 at t= 4ms? Homework Equations I...
  3. Bassa

    Initial Voltage in an RC circuit with a Current Source and no Voltage Source

    Homework Statement [/B] Derive an expression for vc(t) in the circuit of Figure P4.13 and sketch vc(t) to scale versus. I attached a screen shot of the circuit for this problem. time. Homework Equations V = IR V = V0exp(-t/tau) The Attempt at a Solution [/B] I am trying to find the...
  4. terryds

    Calculating Charge and Potential in a Series RC Circuit

    Homework Statement An electric circuit is shown as above. The switch S is closed for a long time and the current flowing is constant. Given that C1 = 3 μF, C2 = 6 μF, R1 = 4 kΩ, R2 = 7 kΩ If the power at R2 resistor is 2,4 W a) Determine the charge at C1 b) When the switch is opened, after...
  5. M

    What is the potential at the top of R2 in this circuit?

    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 = 41 Ω, R3 = 68 Ω and R4 = 154 Ω. The capacitance is C = 49 μF and the battery voltage is V = 12 V. The positive terminal of the battery...
  6. Mausam

    Capacitor question -- charging time for an RC circuit

    Homework Statement Hello everyone , this question has been troubling me for weeks,so if anyone could please help me out.i have attached the pic of the question.The answer given is 2 seconds but i am getting a different answer. Homework Equations first of all i distributed the charge on the two...
  7. C

    RC circuit black box circuit modeling

    Homework Statement I have a red mystery box which contains a 20, 50, 100, and 200,000 ohm resistor (one of each and ONLY one.) There are three terminals on the box you can plug a voltmeter into... testing A-B I got 60k, testing A-C I got 140k, and testing B-C I get 120k ohms. So this is a bit...
  8. M

    Finding Resistance in RC Circuit

    Homework Statement In a simple RC circuit the current as a function of time behaves in the following manner: I(5s) = 8.823 I(10s) = 7.788 I(20) = 6.065 I(30) = 4.724 I(40) = 3.679 I(50) = 2.865 I(60) = 2.231 I(70) = 1.738 I(80) = 1.353 I(90) = 1.054 I(100) = 0.821 I(110) = 0.639 Assuming...
  9. A

    Thevenin resistance in an opamp RC circuit

    Homework Statement In the figure given what is the Thevenin resistance between the nodes of the capacitor?? Homework Equations The Thevenin resistance is the open node resistance between two points. The Attempt at a Solution The way I see it, R2, Rf and R1 are in series and that combination...
  10. H

    Discharging capacitor in RC circuit, confusing path

    Homework Statement The circuit in the figure below has been connected for a long time. Let R1 = 8.20 Ω and R2 = 4.40 Ω. (a) What is the potential difference across the capacitor? (b) If the battery is disconnected from the circuit, over what time interval does the capacitor discharge to...
  11. H

    RC Circuit and current from a discharging capacitor

    Homework Statement In the circuit of the figure below, the switch S has been open for a long time. It is then suddenly closed. Take = 10.0 V, R1 = 56.0 kΩ, R2 = 200 kΩ, and C = 14.5 μF. (a) Determine the time constant before the switch is closed. (b) Determine the time constant after the...
  12. davidhowie34

    How to find magnetic field in a square coil next to an RC circuit

    Homework Statement 1. (35 pts) You have a coop job helping to test a capacitor energy storage system. There is a rather large capacitor with capacitance, C = 2.02F. It is charged to a potential V = 602.V with the polarity of the capacitor as shown. The large, solid line on the right of the R–C...
  13. H

    Generic RC circuit problems?

    Homework Statement In the figure below, suppose the switch has been closed for a time interval sufficiently long for the capacitor to become fully charged. (Assume R1 = 11.0 kΩ, R2 = 22.0 kΩ, R3 = 4.00 kΩ, and C = 11.0 μF.) (a) Find the steady-state current in each resistor. (b) Find the...
  14. H

    Having trouble rearranging this RC circuit

    Homework Statement Switch S shown in the figure below has been closed for a long time, and the electric circuit carries a constant current. Take C1 = 3.00 μF C2 = 6.00 μF, R1 = 4.00 kΩ, and R2 = 7.00 kΩ. The power delivered to R2 is 2.30 W. (a) Find the charge on C1. (b) Now the switch...
  15. R

    RC Circuit with a voltage source

    Homework Statement A voltage source E_0 cos ωt is connected in series with a resistor R and a capacitor C. Write down the differential equation expressing Kirchhoff’s law. Then guess an exponential form for the current, and take the real part of your solution to find the actual current...
  16. RoboNerd

    Figuring out why experimental results are different

    Homework Statement Hello everyone, I am trying to figure out how to approach part c, parts i and ii Homework Equations OK. I know that we have the current equation in milliamps as shown above The Attempt at a Solution My problem is giving one possible explanation for the finding and...
  17. Z

    Engineering Find v(t) and i(t) in the RC circuit

    Homework Statement Homework Equations Voltage Division v2 = vs * (r2/(r2+r1)) KCL - sum of all currents at a given node is 0 V= i * r The Attempt at a Solution [/B] This is my solution...
  18. Blockade

    Need help with voltage across a capacitor in a DC circuit

    In a RC circuit is voltage through a capacitor always consider negative no matter if you're going with or against the current when setting up a voltage equation?
  19. sammyqw

    Engineering DC state RC circuit Find Vc(0)

    Homework Statement Find Vc(0) Homework Equations Nodal Eq , ohms law The Attempt at a Solution Can someone please check my work for Vc(0)? I'll appreciate it.
  20. sammyqw

    Discovering Vc(0) using Nodal Analysis - Check out my Solution!

    Homework Statement Find Vc(0) Homework Equations Nodal analysis The Attempt at a Solution
  21. sammyqw

    Engineering RC Circuit Problem: Hi, Is Capacitor Replaced by Short Circuit?

    Homework Statement 2. Homework Equations [/B] KCL, Node Analysis , Mesh Currents The Attempt at a Solution Hi, in part b when t>0 the capacitor is replaced by an open circuit , however in part c the capacitor is replaced by a short circuit why is that?Aren't inductors the only ones...
  22. M

    Determining the capacitor value for an RC circuit

    hi, i have a question which i was hoping someone could help with,a series circuit featuring a capacitor (C) charging via a 1Mohm (R) resistor and a 12volt dc supply(VS).i know the equation to describe VC is VC=VS(1-e -t/RC)the question is: assuming VC is 2V after a time of 4 seconds, determine...
  23. T

    Engineering Problems with First order RC circuit

    I have problems with question b. I don't know where to start. If the switch is on steady state, the current through capacitor would be 0 and i can't have K. This makes me confused. This is the Total response function of a): V0(t) = K^(-1/2t)
  24. E

    How to graph amplitude vs. frequency for a Low-Pass Filter?

    Homework Statement For my lab class my professor wants us to graph the theoretical amplitude of the output from a low-pass filter vs. frequency. I have the resistance and capacitance that I chose for the RC circuit and a V(in). Is there an equation that I should be able to use to relate these...
  25. T

    RC circuit, finding voltage across a capacitor

    Homework Statement I am trying to find the capacitor voltage in the following picture: Find i(t) in the figure below. Assume dc steady state conditions are valid for t<=0. Homework Equations i=c(dv/dt) KCL The Attempt at a Solution At t<0 I found Vc to be 8 volts which should be correct...
  26. goonking

    Engineering RC circuit with current source

    Homework Statement Homework EquationsThe Attempt at a Solution so when t=0, the capacitor is a closed circuit. The Req of the circuit is (20k)(30k)/(20k+30k)= 12000 ohms. U = I Req = (7.5x10-3A) (12000 ohms) = 90 Volts so there is a voltage drop of 90 volts across the 20k resistor (R1)...
  27. M

    The battery equivalent internal impedance equation

    Homework Statement Hello, long story short: I need to create a model of Li-Ion battery and I'm stuck on calculating the battery equivalent internal impedance. The thing is, I don't know the equation or even how to make one. However, I have a circuit drawing: Homework Equations Values in...
  28. D

    Engineering Diode - RC circuit differential equation

    Homework Statement I'm having difficulty deriving the differential equation, this is what I have so far. In order to solve it, I will be using Matlab, and I'll be using the equation dy/dx ≈ (y(x + dx) - y(x))/dx. Is my derivation correct so far? Homework Equations In picture. The Attempt at a...
  29. S

    Engineering Impedance angle in RL and RC circuits

    Homework Statement This isn't so much of a problem itself but I found it interesting that on the All About Circuits website, two of the questions give a phase angle for impedance as opposite the angle of current. I understand the current is 90 degrees out of phase with voltage in both RL and RC...
  30. F

    Complex RC Circuit - Multiple Resistors

    Homework Statement I have the answer to this question, but I'm trying to understand how to do it. It's a simple circuit: https://onedrive.live.com/redir?resid=6CDEB7909E9460BA!57382&authkey=!ALscxM1v2OtHZIg&v=3&ithint=photo%2cPNG (note: Image inserted in-thread by moderator) The questions...
  31. A

    Engineering Solve 2 Loop RC Circuit: Find Q(topen)

    1. Situation and Variables: A circuit is constructed with four resistors, one capacitor, one battery and a switch as shown. The values for the resistors are: R1 = R2 = 30 Ω, R3 = 66 Ω and R4 = 113 Ω. The capacitance is C = 64 μF and the battery voltage is V = 12 V. The positive terminal of the...
  32. V

    Circuit with three capacitors

    Homework Statement A potential difference of V = 38.0 V is applied across a circuit with capacitances C1 = 4F, C2 = 5F, and C3= 2F, as shown in the figure. What is the magnitude and sign of q3l, the charge on the left plate of C3 (marked by point A)? What is the electric potential difference...
  33. P

    Capacity with 2 R in RC circuit

    Homework Statement Initially we had a circuit with 2 transistor , we draw the equivalent circuit in the dynamic range and low frequency . After that we simplified the Circuit by calculatuig Rin after the capacity . So what we have left is a voltage source (ac) followed by a resistor followed...
  34. N

    How I find value of U on R2 long time after switch is closed

    https://qph.is.quoracdn.net/main-qimg-c22d8aa4be4fc2ed9b2f1c7060982e04?convert_to_webp=true How to find value of U on R2 long time after switch is being closed? Capacitors are charged so there is no current going through? Or? I used kirchof rule so i get Uo+Uc1-U=0 U=Uc1+Uo...
  35. G

    When Is the Potential Across a Capacitor Equal to That Across a Resistor?

    Homework Statement . Switch http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c27/math/math152.gif in Fig. 27-63 is closed at time http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c27/math/math164.gif, to begin charging an initially uncharged...
  36. kostoglotov

    RC Circ, Capacitor charging Q....very lost

    Homework Statement Homework Equations Series: R_{eq} = R_1 + ... + R_n Parallel: R_{eq} = \left(\frac{1}{R_1} + ... + \frac{1}{R_n} \right)^{-1} Charging Capacitor: I = I_0 e^{-t/RC} Charging Capacitor: \Delta V_C = \varepsilon (1- e^{-t/RC}) Charge: Q = C \Delta V_C The Attempt at a...
  37. Y

    Solving an RC circuit using explicit euler

    Homework Statement Hi there. I have a simple RC circuit with a battery voltage of 10 V, R = 1 Ω, C = 1 F and a switch. I want to use the Explicit Euler (forward divided difference) to solve the equation and check for stability, rather than using a ODE. I am finding the equation for when the...
  38. Rath123

    Calculating Time Constant in Parallel Plates: Keeping the Capacitor Constant

    How can a time constant, in parallel plates, be the original value without changing the capacitor?
  39. Rath123

    Is the Time Constant Affected by Changing Plate Distance in an RC Circuit?

    If, by some means, the distance between the parallel plates of the capacitor is reduced to half of what it was before, would the time constant change? If yes, then what would be the new time constant?
  40. K

    Understanding Integrals and the Importance of Constants

    Homework Statement Suppose an RC series circuit has a variable resistor. If the resistance at time t is given by by R = a + bt, where a and b are known positive constants then the charge q(t) on the capacitor satisfies (a+bt) q' + (1/C)q = V where V is some constant. Also q(0) = q_0 Find q(t)...
  41. Y

    Derivation of cutoff frequency for RC circuit?

    How is it derived? The cutoff frequency is Fc = 1/2piRC. R = resistance, C = capacitance. I read somewhere it has to do with Laplace Transforms, but I'm not sure where to go from here. It kind of irks me to just accept this equation without some proof. Thanks!
  42. R

    Electricity and Magnetism RC Circuit Conceptual Questions

    Edit: sorry i realized i posted this in the wrong section. Can some move it to hw? Thank you. Hey i was studying intro E&M recently and i started learning about RC circuits. Up until this point everything, concept wise, has made sense for me. Then I learned how RC circuits work, and the math...
  43. A

    Solve RC Circuit Problem: 45V -> 10V in 4.21ms

    Homework Statement I have an RC circuit with two capacitors connected in parallel. Both capacitors are initially charged to 45.0 V. a.) How long after closing the switch S will the potential across each capacitor be reduced to 10.0V? Knowns: C1= 15.0 microFarads C2= 20.0 microFarads R1= 30.0...
  44. Luke Cohen

    Solve RC Circuit Question: Initial and Long-Time Battery Current

    Homework Statement Switch S, shown in the figure below, is closed after having been open for a long time. 1) What is the initial value of the battery current just after switch S is closed? 2) What is the battery current a long time after switch S is closed? Homework Equations V=IR C=Q/V The...
  45. Q

    Voltage across resistors in RC circuit

    Homework Statement Calculate the voltage, current, and power across the two resistors for every second of run 1 in the RC circuit. The RC Circuit: The settings of the circuit: The Graph. The capacitor is charged until it reaches 5.0 V and then discharged until it reaches 1.0 V. This...
  46. G

    Question for Kirchhoff's current law for RC circuit

    Hello. Maybe this is very basic and important question for circuit analysis. Please see the attached image. KCL (Kirchhoff's Current Law) is applied to red arrow-indicated point and I choose the convention that current flowing out from the point is positive. - side of the capacitor is...
  47. Y

    Writing the correct diff. equations for an RC circuit

    Homework Statement Given the circuit in the picture, I need to: a. write a system of diff. equations that could solve the charges on each cap. and current on each resistor, and write them in a vector/matrix form. b. solve the equations for t>>τ Homework Equations Kirchoff's laws, perhaps...
  48. roms05

    Parallel Plate Capacitor with variable Dielectric (water)

    Hi everyone. I have a problem with my device. It consists of a parallel plate capacitor with plates made of galvanized iron. Each plate's area is 1mx1inch. It's connected to a bleeder resistor and basically, the circuit is just a simple RC circuit. The source I'm using is a constant 5V DC...
  49. H

    Engineering Why is the pulse width in an RC circuit larger than expected?

    Hi, I have a question. So, I've built this simple RC circuit. Of course, the pulse width is then obtained from the oscilloscope. But, according to equation Vo(t) = E(e^(-t/RC)), the value t (pulse width) is larger. Considering the resistor, condenser, Voh, Vil, IC delay, and others, how should I...
  50. E

    AP Physics C E&M RC circuit FRQ

    Homework Statement http://apcentral.collegeboard.com/apc/public/repository/_ap06_frq_physicsc_em_51784.pdf Please please check out Q2 part (d) on this test Homework EquationsThe Attempt at a Solution I understand that before S2 is closed, current through the circuit is zero. As soon as S2 is...
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