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. 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...
  2. 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...
  3. 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...
  4. E

    Parallel RC Circuits: Charging to 0.75V in Seconds

    Homework Statement A parallel combination of 0.1M Ω resistor and a 10 μF capacitor is connected across a 1.5 V source of negligible resistance. The time (in seconds) required for the capacitor to get charged upto 0.75 V is approximately (A) ∞ (B) ln 2 (C) log 2 (D) Zero Homework Equations...
  5. T

    Confused about solving RC circuits with nodal analysis

    Problem is in the picture below. The problem is already solved, but I am confused as to why C(dv/dt) is positive and not negative, since the current is coming out of the capacitor and towards the point v(t), which is not away from v(t) like the solution shows. But if I solve the problem with...
  6. 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...
  7. Metals

    Propellers on an RC Quadcopter?

    Hey forum, So I plan on creating a remote controlled quadcopter and I have a query regarding its propellers' sizes. I read that small propellers require motors with a high KV (RPM per volt), and large propellers need motors with a lower KV. There seems to be a way of determining how to match...
  8. F

    Solve RC Impulse Response: Voltage @ a RC Circuit

    Hello. I would need some clarifications about the impulse response of a RC circuit. 1. Homework Statement Find the impulse response relative to the vc(t) voltage. NOTE: delta(t) is the exact dirac's delta of infinite amplitude, not an approximated peak. Homework Equations δ(t) = d θ(t) /...
  9. E

    Difference between RC and CR circuits

    What would be the difference in measuring voltage across the resistor in this position and when resistor and capacitors positions are in different order? And why? http://people.sinclair.edu/nickreeder/eet1150/PageArt/RCcircuitSimple.gif
  10. 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...
  11. B

    Understanding RC Planes: Scaling Down & Performance

    This question is slightly related to my other plane, but I didn't want to post in the same thread as I didn't want the other one to get derailed. If I have blueprints for an RC plane, and I scale down everything by a ratio (let's say 1/2), would it still work just as well? Or would it follow...
  12. B

    Impedances of R, L, C, RL, RC, LC and RLC circuits

    Homework Statement In first place, ignore the source in each circuit, ignore if make sense or not. I placed one sorce in each circuit just for the circuit be more visible. In second place, ignore the numerical values of the sources, resistors, capacitors and inductors. Think R, L and C in...
  13. 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...
  14. 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...
  15. davidbenari

    Analyzing RC response with convolution theorem and fft.

    Some textbooks like (Numerical recipes the art of scientific computing) derive the DFT as a Riemann sum of the CTFT. With this in mind it would be natural then to approximate the identity ##y(t)=x*h=\mathcal{F}^{-1}\big\{XH\big\}## with the mathlab code y=ifft(fft(x).*fft(h)) which roughly...
  16. J

    Significance of RC time constant

    In a simple series RC circuit, when t=RC, the voltage across the resistor and capacitor is the same. Why is this physically significant and why do we choose this as the time constant that dictates the cutoff frequency?
  17. 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...
  18. 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?
  19. B

    RLC, RL, RC and LC circuits and ODE

    Look this schematic picture: S means source and can be a current source or a voltage source. C_1, C_2 and C_3 are linear components, can be resistor, capacitor and inductor. In the everycircuit, I tried set up all possible combination and the everycircuit denied some combinations, but...
  20. 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)...
  21. 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!
  22. 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...
  23. 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...
  24. 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...
  25. 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...
  26. 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...
  27. 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...
  28. 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...
  29. 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...
  30. Destroxia

    Solving RC & RL Circuits Homework

    Homework Statement 1.) If the time to achieve ½ the maximum voltage across the capacitor in an RC circuit is 0.45 s, what is the capacitance in the circuit if the resistance is 150 ohms? 2.) For an RL circuit, the voltage across the inductor drops from 4.0 V to a constant 1.5 V as a current...
  31. B

    Question on capacitors in an RC circuit

    Homework Statement All information is given in the picture posted Homework Equations V=IR , Q=CV The Attempt at a Solution What I don't understand is , when the capacitors are initially uncharged , they should just be treated as wires , if this is the case , then the entire circuit is...
  32. A

    RC Circuit with a Switch: Potential and Charge Analysis

    Homework Statement Two resistors and two uncharged capacitors are arranged as shown above. Then a potential difference of V0 = 12 V is applied across the combination as shown. a. What is the potential at point a with S open? (Let V = 0 at the negative terminal of the battery.) b. What is the...
  33. T

    Brake design for a small RC car

    Hi! For a university project I have to design a braking mechanism for a remote controlled car. I have very little experience in designing constructions, so I thought I'd ask here for any advice on the matter. I'm mostly curious about the design pattern, the thought process I should be going...
  34. BarelyOtaku

    Engineering RC circuits, a step skipped in solution

    Homework Statement . [/B] This is problem 7.45 in Fundamental of Electric Circuit 5th edition. 2. Homework Equations First off, I want to go ahead and say that I don't need the solution I already solved it. I went ahead and used Nodal analysis when Vs = 30. I placed a node voltage right...
  35. I

    First order RC: Find Unknown DC Circuit, given current graph

    Homework Statement Homework Equations [/B] Tao = R(th) C The Attempt at a Solution The unknown DC circuit model consists of a V(th) and R(th) Tao = (R(th) + 3000) C , total resistance of circuit is R(th) + 3000 0.004 = (R(th) + 3000) (1x10^-6) R(th) = 1 kOhm The V(th) should oppose the...
  36. A

    Solve RC Transfer Function with R=C=1

    Homework Statement R = C = 1; Homework Equations G(S) = 1/(s+1) The Attempt at a Solution Suppose R = C = 1 then the transfer function from the input voltage to the voltage across the capacitor is 1/ (s+1). So Vc(S) / V(S) = 1/(s+1). Getting back to time-domain: Vc(t) = V(t) * e^-t. What's...
  37. T

    What happens to the charge on the capacitor as time goes to infinity?

    Homework Statement Homework Equations q(t) = Cε(1-e^(-t/RC)) The Attempt at a Solution for part a) the instant the switch is closed there is no charge on the capacitor so I am pretty sure I can ignore it for this part and use keirchoffs rules to find the currents through each resistor...
  38. minimario

    RC Circuit Current Help: Equations and Attempt at Solution

    Homework Statement Homework Equations ##q = Q(1-e^{\frac{-t}{RC}})## The Attempt at a Solution Don't know where to start...
  39. A

    Parallel RC transient response

    Homework Statement An accelerometer is connected via a length of coaxial cable to an amplifier. The arrangement is modeled by: (a) a Norton generator in parallel with a capacitor (CP) representing the piezoelectric crystal within the accelerometer; (b) a lumped capacitor (CC) representing...
  40. T

    How can I use 2D airfoil data for calculations in my RC helicopter project?

    Hi everybody, I am a native of Bhutan and have been always contemplating on building a RC helicopter for myself. In this regard,I have studied helicopter aerodynamics and want to swing into action. The momentum theory seems a bit easy to comprehend and perform calculations there. But I'm unsure...
  41. V

    Time Constant, Maximum Charge, and Current in an RC Circuit

    Homework Statement [/B] With a 12V battery, a 5.00µF capacitor and a 8x105Ω resistor determine the following: a) The time constant of the circuit b) The maximum charge on the capacitor c) The maximum current in the circuit d) The charge on the capacitor as a function of time, q(t) e)...
  42. S

    RC Circuits, how do you solve for V(infinity)?

    Homework Statement Question is attached below Homework Equations v(t) =v(infinity) + [v(t0)-v(infinity)]e^[-(t-t0)] The Attempt at a Solution For t<0, you get the circuit where it is only Rt, R, and C, but in dc circuits, the capacitor is an open circuit, does this mean v(t0) =0? For t>0 the...
  43. F

    Need help analyzing an RC circuit

    Homework Statement The circuit contains an ideal battery, two resistors and a capacitor (C= 250 μF).The switch is closed at time t = 0, and the voltage across the capacitor is recorded as a function of time as shown in the graph. Homework Equations time constant = RCThe Attempt at a...
  44. J

    Determining RC EDF Motor Parameters

    Hello All, I am new to the field of electrical ducted fan (EDF) jets and am currently working on a new aerodynamic design using SolidWorks and Flow Simulation for aerodynamics testing. For my computer model, I can enter data for a fan that I would like to use for the thrust of my models, and my...
  45. Logan Land

    MHB Voltage Across 10, 20uF Capacitors in RC Circuit

    Two capacitors of value 10, 20 microfarads are connected in series. Then charged with a 100 volt battery. If the capacitors is disconnected from the battery, and then connected to a 2500 ohm resistor, what is the voltage across the capacitors after 1 second?
  46. T

    Analyzing Current in RC Circuits: A Scientific Approach

    Homework Statement In the circuit below the switch is initially open and both capacitors initially uncharged. All resistors have the same value R. a.) Find the current through R2 just after the switch is closed. b.) Find the current through R2 a long time after the switch has been closed. c.)...
  47. L

    Optimizing Camera Flash Performance: The Role of RC Circuits

    Homework Statement Consider the following circuit in a camera flash where a light bulb is in series with a charged capacitor: a) Derive, but do not solve, the governing differential equation for the circuit. (Hint: treat the resistor and the light bulb as a single resistance.) b) Assume...
  48. Dr. Ficus

    How can the log in the denominator of the charging equation be simplified?

    Homework Statement Basically, I'm just trying to verify that I can do basic algebraic manipulation correctly. The objective: solve the charging equation of a simple RC circuit for (C), capacitance. Homework Equations v\left(t\right)={v}_{s}\left(1-{e}^{{-t}/{RC}}\right) The Attempt at a...
  49. P

    Full wave rectifier with RC Load

    Hi, I am trying to model a full wave single phase thyristor controlled rectifier feeding a resistor and capacitor in parallel (like a power supply I believe where the capacitor is used for smoothing?) and I would like to calculate the average output dc voltage in a similar fashion as for a...
  50. N

    Engineering Coupled RC circuits with AC current source

    Homework Statement Hi, I already asked a question close to this, but now I have different conditions. This is the circuit C_1 = C_2 \\ R_1= R_2 The current is an AC , and I would like to know the voltage at R_1 and at R_2 I made some progress but I do not really know hot to continue...
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