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. A

    Calculating Charge, Current, and Energy in a Simple RC Circuit

    The values of components in a simple RC circuit in series with a key are: C = 1x10^{-6}F, R=2x10^{6} Ohm and epsilon = 10 V. 10s at the moment after the key is closed, calculate: a) the charge in capacitor b) the current in the resistor c) the rate at which energy is stored in capacitor d)...
  2. O

    A beginning RC circuit that resembles a wheatstone bridge

    Everybody knows what a wheatstone bridge looks like. R1 and R2 are on top and R3 and R4 are on bottom and R5 is in the middle of the angled box shape. let's replace R1 and R2 with 2 different capacitors. Let's also replace R5 with a switch. How would you figure out the potential...
  3. D

    RC Circuit/Current/Resistance Problem. Circuit Gurus come here

    Homework Statement In the circuit of the figure below, script e = 2.0 kV, C = 7.0 µF, R1 = R2 = R3 = 0.61 MΩ. With C completely uncharged, switch S is suddenly closed (at t = 0). (a) At t = 0, what is current i1 in resistor 1? (b) At t = 0, what is current i2 in resistor 2? (c) At t = 0...
  4. W

    Laplace help on a DC transient RC circuit

    Laplace help on a DC transient RC circuit ? PLEASE -------------------------------------------------------------------------------- I HAVE A RC CIRCUIT WHERE R1=100Kohm and R2=1Mohm and C=2.1micro farads with a Vin =10V, In order to calculate the voltage through the capacitor I...
  5. W

    Engineering Laplace help on a DC transient RC circuit ? PLEASE

    I HAVE A RC CIRCUIT WHERE R1=100Kohm and R2=1Mohm and C=2.1micro farads with a Vin =10V, In order to calculate the voltage through the capacitor I deduce the following formula, Vc(s)=V/S {(((R2×1/Cs)/(R2+1/Cs)))/(((R2×1/Cs)/(R2+1/Cs)+R1) )} I then need to produce a laplace transform...
  6. J

    Boost Your RC Car's Performance

    01.http://img2.orkut.com/images/milieu/1/1213787033773/32174292/pt/Zpog0ya.jpg How to post image here Its our rc car driven by 3.2 hpi engine 2 speed transmission system, bell crank steering mechanism , fuel use nitro+mthnol its a two stroke engine two wheel drive question:how to increase...
  7. D

    Understanding Capacitors in RC Cars - Demson

    i dismantled a Remote controlled car for its parts and i saw on the electric motor some small capacitors. thats a diagram i know what a capacitor is but in this instance what is its actual purpose? help me please Cheers Demson
  8. D

    Calculate Voltage on Capacitor Over Time with RC Time Constant

    Hi, I have a simple question: if I have a circuit with a capacitor, how do I calculate the voltage on the capacitor in function of time, I mean I know that tau(τ)=RC and there is the general formula X(t)=X(0)+[X(0)-X(∞)]-t/τ. So here comes my question should I consider the capacitor as the load...
  9. E

    Energy dissipated by a resistor in an RC circuit

    Homework Statement Given a series circuit with a capacitor of capacitance C, a resistor of resistance R, a DC voltage source with a voltage V, and an open switch (by open I mean not connected so no current flows through). At t=0 the switch is closed. How much energy is dissapated by the...
  10. J

    How to build an RC circuit for intermittent light bulb?

    RC Circuit -------------------------------------------------------------------------------- Hi guys, I am trying to built an RC circuit in series to light a bulb intermitently. That is on and off in a time interval. Any ideas?
  11. M

    555 Timer RC Charging Capacitor Conundrum

    Hello. I am currently trying to evaluate just how much power the external RC circuitry of a 555 timer uses over 1 cycle. Whilst the capacitor is charging the current falls exponentially. Naturally the voltage also falls through the resistors but this is couteracted by the rise in voltage of the...
  12. D

    Engineering Calculating Output Voltage of an Amplifier with RC Coupling Network

    Hi I am struggling to answer this question: The input coupling circuit of the amplifier shown in the figure consist of an RC network, with R = 1 kW and C = 5mF fed by a sinusoidal voltage source of r.m.s. amplitude of 200 mV. Assuming that the input impedance of the amplifier is, at all...
  13. I

    How to slow down the charge & discharge process in RC battery

    Homework Statement I am trying hard to figure it out how to slow down the charge and discharge current in the RC circuit. If i put the big resistor, it takes long to charge but there is barely any current you can see and also when it discharges. What I am trying to do is, to slow down the...
  14. U

    Calculating Energy Dissipation in an RC Circuit

    Homework Statement The switch in the figure (Intro 1 figure) has been in position a for a very long time. It is suddenly flipped to position b for 1.25 ms, then back to a. How much energy is dissipated by the resistor? the circuit for a is 50V battery, 125 ohm resistor and 20uF...
  15. M

    Where Can I Find Sinusoidal Problems for RC and RL Circuits?

    from where can i get sinosoidal problems of alternate current rc and rl circuits?
  16. V

    Solve RC Circuit Question: Charge Q1(t2)

    Homework Statement All capacitors of the open circuit in fig. 3 are discharged when, at time t=0, the switch S1 is closed. At some point later, at time t = t1, the switchS2 is also closed. What is the charge Q1(t2) on the capacitor C1 at time t = t2 > t1? http://www.vkgfx.com/misc/fig3.jpg...
  17. F

    Calculating RC & LC Time Constants: Series vs. Parallel

    How does the relative position(series or parallel) of a resistor affect the calculation of the RC and LC time constants. In other words is a RC time constant still R\timesC requardless of whether or not R and C are parallel or if R and C are in series. Same question with LC time constants, is...
  18. R

    Engineering Simple RC Circuit Voltage Division Solution

    Homework Statement I think I am turning retarded. For some reason I can't get the right values for a simple voltage division in the s-domain. Find Vout in terms of Vin http://img11.imageshack.us/img11/6325/tardf.jpg Homework Equations The Attempt at a Solution So I do H(s) = (1/s) / ((1/s) +...
  19. B

    How Does Adding a Series Resistor Affect Current Calculation in an RC Circuit?

    Hi, I'm just a humble biologist (writting up a PhD Thesis in Neuroscience) and I'm trying to get a feel for how my equipment works. The circuit for monitoring the current that flows across a cells membrane (in response to an imposed voltage step) can essentially be seen as a resistor, connected...
  20. S

    RC Circuit Differential Equation

    Homework Statement Find the general solution of L \frac{d^2I}{dt^2} + R \frac{dI}{dt} + \frac{I}{C} = \frac{dV}{dt} given L = 0 and V = V_0 cos(\omega t). Homework Equations The Attempt at a Solution So the equation basically turns into a first-order RC circuit equation R \frac{dI}{dt} +...
  21. E

    RC circuit and discharging a capacitor

    Homework Statement RC circuits and discharging a capacitor ok, say I have the following: R = 4700 ohm C = 39 micro farads they are arranged in series and the battery is replaced using a function generator, which we set to produce a square wave (on/off). With any frequencies set. How can I...
  22. D

    Current Through R1 After Closing Switches in RC Circuit

    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 andS2 are open (as shown) and all of the capacitors are uncharged. At time t = 0...
  23. D

    Understanding RC and RL circuits

    Hi everyone. I am having trouble understanding RC AND RL circuits. Specifically the charging and discharging of circuits. The current and charge that goes through the inductor or capacitor at various time(At time=0 or some time after the switch is closed or a long time after the switch is...
  24. C

    RC Circuit - Charge on Capacitor

    Homework Statement In the figure below the battery has an emf of 20 V and an internal resistance of 1. Assume there is a steady current flowing in the circuit. http://img48.imageshack.us/img48/9211/44724253.gif Find the charge on the 4 μF capacitor. Answer in units of μC. Homework Equations...
  25. D

    Launching an RC car off a ramp on a flat roof. Are these computations correct?

    Hi gang, I've been reading for a while and now need some help of my own. Thanks in advance. I'm currently planning a project where I'm going to demonstrate a launch of an RC car off the flat roof of a building. The height of the roof is 25'. I figure the RC car will go 25mph, and the ramp...
  26. P

    Calculating RC Time Constant: R1 or R1 & R2?

    Homework Statement A circuit with a battery that is in parallel with a resistor R1 followed series by a capacitor, which is in parallel with a resistor R2 Homework Equations Time constant = RC The Attempt at a Solution I do not know if it is correct to calculate RC with 1/Req =...
  27. S

    How Do RC Circuits Behave with Capacitors and Resistors?

    Homework Statement http://img301.imageshack.us/img301/9426/55126286.jpg The cirucit shown has been connecteed for a long time. the battery ahs an internal resistance of 1 ohm. 1) Determine the terminal voltage of teh battery 2) Determine the current in the 4 ohm resistor 3) What is...
  28. P

    Solving for Time Elapsed in an RC Circuit

    Homework Statement For the following questions, consider a charging RC circuit, and let the time constant be represented by τ. How many time constants have elapsed when the capacitor has 80.0% of its final charge? Homework Equations I have no clue! i just need a nudge. The Attempt...
  29. C

    RC Circuit and finding Maximum Voltage

    Homework Statement Use the value: E = 200 V, Horizontal resistor R1 = 1136 capital omega, Vertical resistor R2 = 568 capital omega, and Capacitor C = 5.37 mu or micro F, (a) the initial current through the battery just after the switch is closed: (b) the steady state...
  30. P

    Capacitor question( what do prioritize to maximize current in a RC circuit)

    Hello, my last post may have seemed a little too long or complicated apparently, so I'll try to simplify and adjust my questions this time. THE SITUATION: I want to build a circuit comprised of capacitors and a small resistor of 1 Ohm.I link all my capacitors in parallel and I temporarily...
  31. M

    Engineering RC circuit with dc current source

    Homework Statement Solve for the current in each branch of the following circuit as a function of time & derive and expression for the time dependence of teh emf of the constant current source in the circuit below. Homework Equations Zc = Xc = 1/(wC) = t/(2pi*C) The Attempt at a...
  32. X

    What is the total capacitance for the RC circuit lab problem with given data?

    Homework Statement I did the RC circuit lab I measure the actual resistance of 1000Ω Function Generator Resistance: 50 Ω Function Generator Frequency: 1.4Hz resistor used was 41uF in C1 Resistor used was 22uf for c2 So i have to find c1, c2 and use c1,c2 to calc. the total...
  33. D

    Capacitance of circuit & RC time constant

    1. The problem statement http://s685.photobucket.com/albums/vv212/dewdr0p714/?action=view&current=5circuittakehometest1.jpg 1) Determine the equivalent capacitance of the circuit 2) How many RC time constants are needed for the charge on the capacitors to reach 75% of their final...
  34. I

    What Percent of Final Charge Does a Capacitor Reach After 4.5 Time Constants?

    Homework Statement Consider an RC circuit in which a capacitor is being charged by a battery connected in a circuit. Initially the capacitor is uncharged. Then the switch is closed. After a time equal to 4.5 time constants, what percent of the final charge is present on the capacitor...
  35. S

    Inverse laplace of high pass RC filter

    Homework Statement I'm trying to work out the time domain response of a first order high pass RC filter, eg. http://en.wikipedia.org/wiki/File:High_pass_filter.svg I've got two solutions, one using laplace and one using differential equations, but they are different. One equation must be...
  36. N

    Please Explain when an RC Circuit Opens - Effect on a Light bulb

    Homework Statement Initially the switch is closed in the circuit shown and the light bulb is shining brightly. What happens when the switch is opened? (diagram in attached link) 1. The bulb goes out immediately. 2. The bulb gets gradually brighter. 3. The bulb gets gradually dimmer...
  37. J

    3-Step Process of a Simple RC Circuit with Battery and an Open Switch

    The following 3 step process refers to a simple RC circuit with a battery and an initially open switch: 1- the switch is closed, allowing the capacitor to charge; 2- after the capacitor has charged, a slab of dielectric material is inserted between the plates of the capacitor and time...
  38. S

    Drooped down wingtip or the drooped up wingtip better for an RC plane?

    Hi, Can someone pls help me out in telling me whether the drooped down wingtip or the drooped up wingtip is better for an RC plane? I have read that the drooped down wingtip is better but none of the planes in production(commercial airliners) use it. They use the drooped up wingtip! Also, is...
  39. J

    RC Circuit: Time Dependency on Capacitance & Resistance

    Why is time in a series RC circuit linearly dependent on capacitance as charging/discharging time is increased? (same with resistance) I thought RC circuits were exponential.
  40. J

    Engineering First Order Transient: RC Circuit

    Homework Statement http://i.thespiffylife.com/files/1/trans1.jpg i have to find Vc(t) Homework Equations I know that Vc(0+) = Vc(0) = Vc(0-) and Vc = Vs*e^(-t/RC) The Attempt at a Solution What I'm unsure on is what the equivalent resistance of the circuit would be so I could find the...
  41. S

    Archived How Is Energy Distributed in a Series RC Circuit?

    A 0.25mu F capacitor is charged to 50 V. It is then connected in series with a 25ohm resistor and a 100ohm resistor and allowed to discharge completely.How much energy is dissipated by the 25ohm resistor? I know that Q=CV and U=.5CV^2=.5 * Q^2/C Now U is the energy released over both...
  42. S

    Understanding Imax and Qmax in RC Circuits: A Quick Guide

    In the equation I= Imax * e^(-t/RC) When do you use E/R for Imax and when do you use Qmax / RC ?? I have seen them used interchangeably in discharging problems and in charging problems. Are there any guidelines to use one for one type of problem and the other for another type? To me...
  43. J

    Calculating Power Factor for an RC Circuit with Given R, C, and Frequency

    Find the power factor for an RC circuit connected to a 70Hz generator with an rms voltage of 125V. The values of R and C in this circuit are 105ohms and 82.4microfarads, respectively. The equation I think you use is P=IVcos\oslash and also z= square root of R^2+(1/wc)^2 and cos0 = R/Z...
  44. A

    Current Flowing Through RC Circuit (Charging)

    Hey, everyone. Just a quick question here. If I have the following circuit, with it's switch initially opened, what will happen to the current through resistors 1 and 2, after I close the switch? http://img249.imageshack.us/img249/7716/showmeplkh6.gif 1) When the switch is first closed...
  45. djeitnstine

    What are the best wing designs for maximum efficiency in RC planes?

    Hey all I'm at Embry-Riddle now. I'm in a club called SAE Aero. We are desiging an RC plane that should be as light as possible and lift as much weight as possible - the aim 55 lbs. We have to build it from scratch. However right now we are in the design stage. I was wondering if there was...
  46. P

    ANSI RC, LC etc. seems to deal with shifts

    I have a clearance question. I’m in need of understanding the clearances and tolerances associated with the sliding parts in a sliding bolt fire arm. The moles are really going to hate this. After some time goggling, reading, and with a year of mechanical drafting, I estimated that ANSI RC 8...
  47. W

    Measuring Moment of Inertia of RC Helicopter

    Hi guys. I am trying to measure the moment of inertia of a remote controlled helicopter about its 3 principle axes at the centre of gravity. In all of the literature I have read relating to this project, everyone just glosses over this part. What I need to figure out is an experimental...
  48. T

    Simple RC and RL Transfer Functions

    [Solved] Simple RC and RL Transfer Functions Homework Statement Given the transfer function: TF= (200)/(1 + j0.001w) a. Determine the cuttoff frequency in radians per second and in hertz Homework Equations There are a couple other equations like this in the book, but I just...
  49. T

    Understanding RC Circuits with Multiple Capacitors and Resistors: Homework Help

    Homework Statement (a) What is the potential of point a with respect to point b in Fig. 26.61 (V = 16.0 V, R1 = 7.00 , R2 = 4.00 ) when switch S is open? (b) Which point, a or b, is at the higher potential? (c) What is the final potential of point b with respect to ground when switch S...
  50. I

    Build a RC bandpass filter to pass only 60Hz

    I'm wanting to build a RC bandpass filter to pass only 60Hz. But I do not know what capacitors and resistors to use. Can anyone tell me what capacitor and resistors I should use?
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