Rc Definition and 643 Threads

rc (for "run commands") is the command line interpreter for Version 10 Unix and Plan 9 from Bell Labs operating systems. It resembles the Bourne shell, but its syntax is somewhat simpler. It was created by Tom Duff, who is better known for an unusual C programming language construct ("Duff's device").A port of the original rc to Unix is part of Plan 9 from User Space. A rewrite of rc for Unix-like operating systems by Byron Rakitzis is also available but includes some incompatible changes.
Rc uses C-like control structures instead of the original Bourne shell's ALGOL-like structures, except that it uses an if not construct instead of else, and has a Bourne-like for loop to iterate over lists. In rc, all variables are lists of strings, which eliminates the need for constructs like "$@". Variables are not re-split when expanded. The language is described in Duff's paper.

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  1. I

    RC Circuits, time to charge a capacitor

    Homework Statement Switch S in the figure below is closed at time t = 0, to begin charging an initially uncharged capacitor of capacitance C = 13.0 µF through a resistor of resistance R = 24.0 . At what time is the electric potential across the capacitor equal to that across the resistor...
  2. P

    How Does an RC Circuit Behave During Charging and Discharging?

    Let's say you have a circuit with a resistor, capacitor and voltage source and a switch. I got a few questions. 1. The instant the switch is closed, the voltage drop would all be across the resistor right? 2. After a long time the switch is closed, the current would approach 0 and the...
  3. 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...
  4. P

    Help with RC Circuits: 3 Resistors in Series

    Homework Statement I attached the problem I don't understand why the 3 resistors at the top end up being in series for part b. can someone explain that to me. Homework Equations The Attempt at a Solution
  5. 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...
  6. 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...
  7. 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...
  8. M

    Creating a RC Controlled Motor for Dyno Machine

    Hello all. I have a mini project on hand which is to create a remote controlled motor which in turns control the throttle cable of a dyno machine. I have a plan on hand which is to use an RC motor connected with a pulley. however to control the speed of the motor, i know that a transmitter...
  9. R

    How if the small RC helicopter Hover but the train is moving?

    How if the small RC helicopter Hover at inside center of the train . the train is moving constant velocity. will the helicopter moving backward?
  10. A

    What is the Range of w for Equivalent Series and Parallel RC Circuits?

    Given : a series RC circuit with Rs and Cs and Parallel circuit with Rp and Cp...also given both are equivalent and Q-factor is high. Calculate the range of w for both circuits are equivalent. pls help asap...
  11. 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...
  12. H

    Converting Rotor Frequency to Helicopter Thrust: Finding the Missing Equation

    Homework Statement I am doing an EEI relating to how the ground effect influences an RC helicopter's thrust. Homework Equations Are there any equations for converting the frequency of a helicopter's rotor blades to the power used? or alternatively is there another way to calculate the...
  13. L

    What is the role of RC in opamp feedback loop for Type 2 opamp compensators?

    I am trying to understand Type1, 2 and 3 opamp compensators used in DCDC converters. Type 1 is just an opamp integrator. Type 2 has a C in feedback loop with parallel RC. How does this boost the phase Margin? (page 307 - http://tinyurl.com/3qyt5dc) I understand phase and gain margin when...
  14. 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...
  15. 0

    What is the Charge on Capacitor C2 at Time t2?

    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...
  16. C

    Charging of capacitor through rc and with pulse

    Hi quick question, I have an rc circuit which is to be charged with an input voltage of 3.6 V but what happens if a pulsing current source is connected to the capacitor as well? So I have a rc circuit but also a pulsing current source connected directly to the resistor. I have attached the...
  17. J

    Additivity of Time Constants in Series RC Circuits

    Does anyone know of any instance where the the time constants of two RC circuits in series is additive. It seems that when R1=R2 and tao1~tao2 this holds?
  18. K

    How Can a Capacitor be Charged to the Voltage of the Battery in an RC Circuit?

    Resistor Capacitance Circuits.Say there is a resistor before a capacitor connected in a wired circuit; and there is a battery as the emf source (10V for example). How can the capacitor be charged to approx. the voltage of the battery if the voltage drop across the resistor = the voltage of...
  19. P

    Jump into the Field of Remote Control (RC): How Difficult?

    Since I last posted here, I've experimented with small DC motors, parallel and series circuits, messed with my electronic-building kit, and even did a little Job Shadowing (temporary internship) at a local electrical engineering place for school. I definitely want to make this into a profession...
  20. 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...
  21. N

    How Is the Time Constant Calculated in a Series-Parallel 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...
  22. 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...
  23. H

    What Is the Resistance Value in an RC Circuit with a 37V Drop After 2 Seconds?

    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...
  24. D

    How Do You Prove and Analyze 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...
  25. M

    What is the RC time constant for this problem?

    See attachment for problem. I am stumped on how to find the rc time constant in this problem. Please help me get started. Thanks.
  26. M

    What are the practical applications of RC circuits?

    We are studying RC circuits in my physics class and I'm just curious as to what they are even for? My instructor challenged us to go find 5 uses for RC circuits and I am stumped. I can't even find any on google. Anybody know of any?
  27. 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.
  28. 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...
  29. 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...
  30. 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 =...
  31. 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...
  32. R

    Engineering Solved: RC First Order Circuit Voltage Drop after Switch Opens

    Homework Statement Find the voltage drop across the capacitor just after the switch is opened v(0+) Most variables are in picture attached C = 100mF Homework Equations Vc(t)= Vc(\infty)+[Vc(t+)-Vc(\infty))*e-(t-t1/\tau) The Attempt at a Solution First i assumed that the...
  33. M

    Solve RC Circuit Problems: 2.00μF Capacitor, 1.3 kΩ Resistor

    Homework Statement A 2.00μF capacitor with an initial charge of 5.10μC is discharged through a 1.3 kΩ resistor. a) calculate the current through the resistor 9.00ms after the resistor is connected across the capacitor b) what charge remains on the capacitor after 8.00ms c) what is...
  34. F

    RC circuit problem with time constants

    Homework Statement http://img193.imageshack.us/img193/3696/aasdff.th.png Uploaded with ImageShack.us The Attempt at a Solution (a) No current, so no time constant since C = 0 for it stores no charge (b) Current immediately is driven through so \tau = (R_{1}+R_{2})C (c) I pulled the...
  35. C

    Why is the RC circuit homework statement giving different results than expected?

    Homework Statement The Attempt at a Solution As at t=0 the capacitor behaves as a wire ... so the circuit at t=0 will be like: q at any time for this circuit will be, q \ = \ CE(1-e^{-t/\tau}) + Q_oe^{-t/\tau} differentiating it will give current, i \ = \ \frac{Ee^{-t/\tau}}{R} \ - \...
  36. J

    DC & RC Circuits: Proving Energy Distribution

    In the RC circuit shown, the resistance R, the Capacitance C, and the emf of the battery are all given quantities. The battery does not have internal resistance and the capacitor is fully charged after the switch is closed. Prove analytically that, regardless the values of R and C, exactly 50%...
  37. T

    Rates of Change in a RC Circuit

    Homework Statement A 2.9 MΩ and a 2.8 μF capacitor are connected in series with an ideal battery with an EMF of 3 V. At 2 seconds after the circuit is initially connected to the battery: What is the rate at which energy is being stored on the capacitor? Homework Equations dq/dt = v/r *...
  38. L

    Problem with 'simple' RC circuits

    Hey there! First post, been browsing through the forums for a little and I have found problems like this, but I still am getting the wrong answer when I try and do the things suggested. Circuit is simple, and in series. Vs = 23 V R1 = 87 Ohms C=6.1 microfarads with a switch, of course...
  39. A

    Calculating Current in RC Circuit with Closed Switch

    Homework Statement What is the current through R2 immediately after the switch S is closed? C = 7.95x10^(-6) F , R1 = 27.5 Ohm , R2 = 10.5 Ohm , and Vo = 20.0 V Homework Equations I don't know what to use? The Attempt at a Solution I thought maybe I use two loops, the left and...
  40. D

    AC Power RC series circuit low pass filter, find frequency given gain.

    1. You have a series circuit consisting of a ac power supply, a 600 ohm resistor and a 73 nF capacitor. If the circuit is configured as a low pass filter, what frequency will cause the gain to be 0.25? 2. If the circuit is configured as a high pass filter, what frequency will cause the gain...
  41. U

    Sum of potentials across a resistor in series with parallel RC

    Homework Statement We have built a circuit with an ac source containing a resistor in series with a parallel RC combination, we have measured the voltage across the first resistor and the voltage across the RC combination with a high and a low frequency. 80Hz: V0 = 2,325 V en Vm = 2,780 V...
  42. P

    RC Circuit/Kirchhoff rules question?

    RC Circuit/Kirchhoff rules question?? Regarding the loop rules. I am trying to solve a problem with 2 batteries, 3 resistors and one capacitor. I know the rules regarding the loop and traversing resistors and batteries. My question is, what happens when the direction of current I choose...
  43. P

    RC Circuit: charges on two capacitors

    Homework Statement At t=0m the switch is open and both capacitors are uncharged. What are the charges on each plate (magnitude and sign) of each capacitor long after the switch is closed and capacitors are fully charged? Homework Equations q=C E(1-e^(-t/RC) The Attempt at a Solution...
  44. Q

    Capacitors in RC filtering

    in AC source, C and R in parallel, why does the capacitor discharge when the voltage across the resistor decrease ? [PLAIN]http://upload.wikimedia.org/wikipedia/en/thumb/2/27/RC_Parallel_Filter_%28with_I_Labels%29.svg/250px-RC_Parallel_Filter_%28with_I_Labels%29.svg.png the Vin is a AC...
  45. T

    Find the Time Constant of an RC Circuit

    Homework Statement Two capacitors (c1 = 11 and c2 = 15 μF) are charged in series by a 11 V battery. Find the time constant of the charging circuit. (r = 4 Ω). Homework Equations V=E(1-e^(-t/T)) Where T=Tau=RC, E is the Voltage of the power source, and V is the voltage of the capacitor...
  46. S

    Engineering Help with Step Response of an RC circuit

    Homework Statement Derive the Voltage and Current equations for Step Response of an RC circuit. Homework Equations End products will be Vc(t) = i(s)R + (Vo - i(s)R)e^(-t/RC) and i(t) = (Is - (Vo/R))e^(-t/RC) The Attempt at a Solution Using KCL on a hypotetical RC circuit with a...
  47. N

    Understanding RC Circuit Behavior: Solving the Natural Log Mystery

    Homework Statement This isn't really a homework question- at the end of my last lab, in which we measured the time required to charge and drain a 10micro farad capacitor with a 100k resistor hooked up to a switch and a 9 volt battery our professor asked us what the natural log of voltage...
  48. A

    Two parallel RC circuits in series

    Hi, got a naive question (not in the electronics area) I have got two capacitors in series when being charged with a DC (I presume the resistors have negligible conductances so I assume the time constant of charging would follow that of a series capacitor circuit), like this, ---||--- (C1)...
  49. D

    Design RC Circuit for V vs Time Characteristics

    Homework Statement Design a RC circuit so it has the same V vs time characteristics *See attached diagram* Homework Equations The Attempt at a Solution I really have no idea how to approach this, but I do know, RC circuit: Vc(t)=Vb(1-e^-(t/RC)) RL circuit...
  50. D

    Designing an RC Circuit for RL Equivalent Voltage vs. Time

    Homework Statement Design an RC circuit that has the same Voltage vs. Time characteristics as the RL circuit shown *See attached Diagram* Homework Equations The Attempt at a Solution Not really sure how to approach this, but all i know is the equations: RC circuit...
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