What is Rc: Definition and 643 Discussions

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. T

    Any one me with mini rc helicopters

    Hi I am an electronics undergraduate and i have been trying to implement an idea which looks exactly as the concept of mini rc helicopters. Ok Now Without any delay i will tell my idea. I really really hope anyone would help me out... Now My Idea is to lift a weight of approx 3-4kgs using...
  2. A

    RC circuits and potential difference

    Homework Statement Circuit is at this link: http://www.colorado.edu/physics/phys1120/phys1120_sp08/hws/capa8_figs/gian1946.gif 1. What is the potential at point a with S open (let V=0 at the negative terminal of the source, and assume it's a long time after the circuit was connected to the...
  3. 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...
  4. 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...
  5. 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...
  6. K

    Optimizing Charging RC Circuits: Lowering Time Constant for Faster Charging

    Homework Statement You need to modify a simple charging RC circuit (power supply, resistor, and capacitor in series) to maintain the same maximum current but lower the the time constant and make it charge faster. Which of the following will accomplish it? A) Same R, lower C. B) Same R...
  7. 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...
  8. T

    Parallel resonance concerning RL and Rc

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  9. B

    Engineering Time variant RC and RL circuits

    Ok so I have some topic overview questions. I think I am on the right track but would like to make sure I am thinking about this the correct way. When I say time variant I simply mean there is a simple switch in the circuit. This is link to a were I found my supplemental material and it has...
  10. 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
  11. 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...
  12. 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...
  13. 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...
  14. 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...
  15. E

    Calculating Axial Torque for RC T-Beam to Cause Shear Stress

    Homework Statement For the reinforced concrete T-beam find what axial torque would cause a shear stress of vt = 0.37 N/mm2 to develop, and so make additional torsional reinforcement necessary according to BS 8110. Use the method indicated in Clause 2.4.4 of BS 8110 of distributing the torque...
  16. 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...
  17. M

    How Long Does It Take for a Capacitor to Discharge in an RC Circuit?

    1. Homework Statement The capacitor in an RC circuit with a time constant of 25 ms is charged to 10 V. The capacitor begins to discharge at t = 0 s 2. Homework Equations τ=RC ΔVC=(ΔVC)e^-t/τ 3. The Attempt at a Solution part a) At what time will the charge on the capacitor be...
  18. 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)...
  19. 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...
  20. S

    Voltage and Current in RC circuits

    Homework Statement A circuit includes a spark gap that connects to the ground. The width of the gap is adjusted so that the capacitor discharges to the ground each time the voltage reaches 99% of the maximum. (The circuit is basically a simple series circuit with an 80v power supply...
  21. J

    How Do You Calculate Initial Current in a Multi-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...
  22. 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...
  23. 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.
  24. 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...
  25. R

    Help understanding RC circuits

    Homework Statement In a problem I have a circuit that I have not set up to know what happens as far as voltages across my battery(4v), two equal resistors and a capacitor. Homework Equations The Attempt at a Solution Because i have not seen a circuit like this I am thinking that...
  26. O

    RC Networks and complex numbers

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  27. P

    RC circuit switching at t=0 from A to B

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  28. S

    Max load on rc cart depending on motor torque

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  29. 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...
  30. W

    Engineering Understanding the Role of Capacitors in RC Circuits

    Homework Statement What causes integration of V_{in} within an RC circuit?Homework Equations Z= R + X_C = R - j/(ωC) Z is the impedance of the circuit, j=(-1)^.5, ω is angular frequency, and C is the capacitance. The Attempt at a Solution I think integration is the capacitor's way of...
  31. 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?
  32. S

    RC Filtering Circuits: Terminals, Vin, Vout & Ground Explained

    Heya! I've got a lab practical tomorrow to do with RC circuits, what do the terminals at the top and bottom of a filter circuit diagram mean, I'm assuming Vin and Vout is the voltage in and then 0V/ground, but what do the bottom two terminals correspond to? Cheers
  33. T

    Solving Transient Analysis RC: Find Capacitance for 200V, 20V, 2V

    1. The problem statement: What is the value of capacitance needed in Fig. 1 so that the voltage across the capacitor never exceeds (a) 200 V, (b) 20 V, and (c) 2 V ? This is the Circuit Homework Equations Vc(0-) = 0V Vc(0+) = 150V ic = c v' vc(t) = final + [initial -...
  34. R

    Is a Rack and Pinion Arrangement Suitable for an RC Car Steering Mechanism?

    hello guys..i'm trying to make my first rc car..but m not getting the steering mechanism for it..is the steering mechanism for real cars applicable on it..?:confused::mad::rolleyes:
  35. 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...
  36. 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...
  37. 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 => |...
  38. 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...
  39. A

    Distortion in rc coupled amplifier

    hi, when i was making a rc coupled amplifier but as soon as i connect the input signal the signal gets distorted.can anyone tell me the reason for that and how to avoid the distortion? thanks,
  40. E

    Engineering Solve RC Circuits Homework: Find Vout w/S1+S2 Closed

    Homework Statement S1 switch - always close. S2 switch is closed, until the capacitor voltage reaches 2V. given: R,C,V values. V0 = 0V. Need to find Vout while S1+S2 are closed and until S2 opens.Homework Equations Vc(t) = (Vi - Vf)*(exp -t/TAU) + VfThe Attempt at a Solution I have found the...
  41. J

    Powering RC Hobby Motor with Integy 7.2V Battery

    Hello all, I have a Integy 7.2V 1600mah battery that powers a RC hobby motor. I was wondering if RC batteries supply constant voltage to the motor for a certain amount of time before they start dieing or if the battery voltage continuously decreases as you power the motor until the battery...
  42. B

    Reactive power, RL RC circuits

    Trying to understand the power network and synchronous machines, led me to the fact that I am not sure about the basics. The terms the generator is delivering or consuming reacting power made me halt. So I went back to my old course(which I allegedly passed) where the reactive power is...
  43. R

    Current after (1) time constant in RC circuits

    Homework Statement Maximum current: I max = 4.62 * 10^-4 A Time constant of circuit: T = 3.9 secondsHomework Equations T= RC The Attempt at a Solution I'm trying to find the current after 1 time constant. Seems simple enough, the current changes by 63%. So (Imax)-(Imax * 0.63) or...
  44. 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 =...
  45. 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...
  46. 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...
  47. 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...
  48. W

    Archived Charging and discharging RC circuits

    Homework Statement The RC circuit pictured below begins with capacitor C completely uncharged. I: What is the current at point A immediately after the switch closes? II:What is the current at point A 'at the end of the quaternary period' (I lol'd when he worded it like that) after the switch...
  49. B

    RC Time Constant Question (Easy)

    Homework Statement A 12.8 micro-F capacitor is connected through a 0.890 M-ohm resistor to a constant potential difference of 60.0 v. Homework Equations q=CE(1-e^(-t/(RC)) i=(E/R)-(q/(RC)) The Attempt at a Solution Compute the charge on the capacitor at the following times...
  50. 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...
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