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

    Engineering Calculating voltage and current of RC Circuit

    Homework Statement Attached. Homework Equations The Attempt at a Solution Attached. I am looking at the circuit at t<0. I need to calculate v(0) but I'm not sure how to apply nodal analysis when you have a capacitor in the circuit. Do capacitors follow ohm's law?
  2. T

    Understanding Oscilloscopes: How Can We Use Them to Measure RC Circuits?

    The biggest problem is that I have no knowledge about the math for oscilliscopes. This is a post lab but all we actually did was push a few buttons to record measurements, we did not go into any detail about the methods, just what an oscilliscope was supposed to measure. Homework Statement...
  3. S

    Confused about Kirchhoff's Laws for RC Circuits - Discharging

    Hi. When trying to derive the equation for voltage across a discharging capacitor in series with a resistor using Kirchhoff's laws, I got stuck. My attempt was that the voltage gain across the capacitor should equal the voltage drop across the resistor, therefore q(t)/C = i(t)*R, or q(t) -...
  4. H

    What is the voltage across the capacitor?

    Homework Statement The figure shows the circuit of a flashing lamp.There is a current through the lamp (see the photo) only when the potential difference across it reaches the breakdown voltage VL; the capacitance DIScharges completely through the lamp. (a)A lamp has breakdown voltage...
  5. T

    Inverter propagation delay using the RC delay model

    Hi~ Actually I am fine with calculating the delay but I haven't got the concept clearly enough. Both nmos and pmos have their equivalent RC models. I understand how the RC model of nmos works when its on or off but I don't get how the pmos turns out this way. When its off, the upper part...
  6. E

    Engineering Transfer function for RC and RL circuits

    Homework Statement I just want to understand, how to calculate transfer function. Here is simple example: Homework Equations The Attempt at a Solution But in this circuit I don't understand how to do it. I have to find T and k as it is in preview. Which is the element for...
  7. H

    RC circuit question: In vs. Out phase angle

    In an RC circuit, the phase angle between the input and output voltages (not current and voltage) seems to be proportional to the amplitude of the output voltage. That is, as the phase angle between input and output goes to plus or minus 90 degrees, the output voltage goes to 0. Why is that?
  8. M

    Engineering Analyzing an RC Circuit: Solving for Time Constants and Resistance

    Homework Statement Ok guys, so this is a slightly long question, but bear with me because I think I figured out most of it. I just need help towards the end. So I have a circuit with a current source in parallel with a capacitor and also in parallel with a resistor (see attached image). This...
  9. O

    Electronics: Plot Vout of RC circuit

    Homework Statement http://imgur.com/OowiMCR As noted in the image: In the circuit below, R1=R2=10kΩ, and C=0.1μF. Plot Vout(t) if the input, Vin, is a step function of height V0 at t=0 Homework Equations Vcap=V0-Ce-t/RC The Attempt at a Solution I was hoping someone could...
  10. L

    RC Circuits, capacitor charges and voltages

    These are 2 stand alone problems, however the answers disagree with one another and I am trying to reconcile their differences. Any insight would be appreciated! :) The answer is C. The answer provided with this question is that "there is no dependence on resistance of any kind". However the...
  11. B

    What is the voltage drop across the resistor in a discharging RC circuit?

    Homework Statement Determine the voltage drop across the resistor when the capacitor has been discharging for 10μs. Capacitance=400 pico farad and is charged to 10v through a 50kΩ resistor. Homework Equations Vr= V*e -t/CR The Attempt at a Solution Vr = V-Vc at the instant of 10μs...
  12. B

    How Does Current Behave in a Discharging RC Circuit?

    Homework Statement Determine the current flowing when the capacitor has been discharging for 5μs Capacitance=400 pico farads which is charged to 10v through a 50kΩ resistor. Homework Equations Vc = ve-t/CR The Attempt at a Solution So Vc =Ve -t/CR -t/CR =...
  13. B

    RC circuit with Schmitt trigger - Derivation

    In lectures I covered how a Schmitt trigger can be used in an RC circuit to determine the capacitance of the capacitor (Where the Schmitt trigger switches at 0.3V+ and 0.6V+). The equation given was that C = 1.2 R \ T (time period) Does anyone know how to derive this or where it comes from...
  14. N

    ODE for 2 RC circuits in series

    Dear all, I have problem to find the differential equation for my circuit shown in the attached picture. For input I have a current source, and the output is the voltage U (the voltage between the first and the ground node). I need the ODE to find the mathematical response of the system...
  15. W

    RC Op Amp phase shifter transfer function/how to get

    Hello, I am trying to figure out the transfer function for an RC phase shifter: http://imgur.com/2dnRYn7 (Picture of circuit) I am not sure how to calculate the output and specifically the phase of the output of this circuit. I understand that I need to consider one of the 'golden rules'...
  16. J

    Engineering RC Circuit Analysis: Find di/dt & Show Current=0 After 1 Time Constant

    Homework Statement Use current equation and find di/dt expression, hence show if initial gradient were maintained the current would be 0 after 1 time constant. Homework Equations I calculated RC to be 0.5s i=0.02e^-t/0.5 The Attempt at a Solution I solved di/dt to be...
  17. F

    Building a RC circuit to pick up radio waves

    Homework Statement Homework Equations w = 1 / sqrt(LC) The Attempt at a Solution hi there, I 1. I decided to choose, 93.3 MHz so 93.3 x 10^6 Hz is my freq. 2. I googled how a band pass filter diagram should look like and I found this, is the only way to create a low...
  18. JJBladester

    Trouble with a Passive RC Twin-T Notch Filter

    Homework Statement I'm trying to understand how Twin-T notch filters work. I get that they are made of two passive RC filters, one low-pass and one high-pass in parallel. The trouble I'm having is how to determine the corner frequencies (where Vout = 0.707Vin). The gain of the corner...
  19. T

    RC Circuit defibrillator Question

    Homework Statement A 140μF defibrillator capacitor is charged to 1500 V. When fired through a patient's chest, it loses 95% of its charge in 40 ms. What is the resistance of the patient's chest? Homework Equations The Attempt at a Solution According to "Mastering Physics," the solution that...
  20. PsychonautQQ

    Bode Plots in RL and RC circuits

    Hey PF! I have a test tomorrow and some of the material is on the basics of RL and RC circuits set up as high pass or low pass filters. Does a High pass filter bode plot look the same whether it's RC and RL? Same with a low pass? Can anybody to an online resource of what bode plots look like...
  21. C

    RC Circuits charging/discharging

    Homework Statement Plot I_r vs. time and Q_c vs. time starting from when the switch is moved from its lower position to its upper position. Label both axes with numbers and units. Show three time constants. Assume that the capacitor is initially uncharged. After the circuit reaches its...
  22. N

    RC Circuit Filtering Halp?

    I bought a biophysics book the other day, and immediately began reading it. Sadly, I'm only 12 pages in now, because I seem to have run up against a wall in my understanding. You see, I don't understand a step being taken in the math, and am not sure what I should learn to understand it better...
  23. L

    RC circuit question(Charging A Capacitor)

    Homework Statement C1= 2.0 μF C2= 5.0 μF the resistor has a resistance of 0.10 MΩ The circuit shows the charging of a capacitor a) At t=0 the switch is closed. What is the initial measuring on the ammeter? b) After the current has decayed to zero what are the voltages at points A,B and C...
  24. O

    Understanding RC Circuits and Voltage Distribution

    Homework Statement Given V R C for the figure, determine a. The voltage of a with respect to b when the switch is open? b. Which point a or b is at a the higher voltage? c. What is the final voltage of point b with respect to ground when the switch is closed? d. Wow much...
  25. E

    Engineering RC circuit differential equations

    Homework Statement Task is to write differential equation for this circuit. Homework Equations The Attempt at a Solution I'll try to solve the task, but now I want to know, is it possible to use voltage source instead of current source. For example, I can calculate ekvivalent...
  26. P

    Engineering Transient Response RC series circuit

    Hi, I have been given a question which involves analysis of a series RC circuit. The system in question has a 4Ω resistor in series with a 1000μF Capacitor (the capacitor is to be considered as completely uncharged before t=0). There is a 12V supply in the circuit. At t=0, a switch is...
  27. U

    Maximum Length for Coaxial Cable in a 100 ns Noise Transfer Scenario

    Homework Statement Signals from sources of different kinds are often very weak and very quick. To minimize the noise risk they're often led through coaxial cables. How long can one [coaxial cable] be if it has the capacitance 80pF / m and resistance 0.04 Ohm/m and you want to transfer noise...
  28. D

    RC DC Series and Parallel Circuit

    Hi! Homework Statement Homework Equations V = IR Kirchhoff Current and Voltage Law. The Attempt at a Solution I am facing difficulty with this RC circuit. I tried looking up solutions but all I could find were either exclusively series or parallel. My first guess was to take Total Current...
  29. Z

    Engineering Finding the Transfer Function of an RC Circuit in the Laplace domain

    Hi, Basically I have circuit with an input Vi (s) across a capacitor C which is in parallel with a resistor R1. And these 2 components are in series with another resistor R2 (please see attached drawing). The question states: Show that the transfer function of the circuit is: Vo/Vi...
  30. E

    Energy Dissipation in an RC Circuit: Finding the Total Thermal Energy

    Homework Statement A capacitor C=8.00*10^-8F which has an initial charge q=1.4*10^-6C starts to discharge through a resistor R=3.00*10^6Ω at time t=0. Determine the total energy W dissipated as thermal energy in the resistor. Hint: use energy conservation. The Attempt at a Solution I...
  31. F

    Series-Parallel RC Circuit Analysis

    I'm having a hard time understanding and solving problems in moderately complex RC circuits... Please Help. You don't have to solve right up to the numerical value, that is not my priority, Rather If you could just explain how to begin and process through the question, It would be best...
  32. F

    Series-Parallel RC Circuit Analysis

    I'm having a hard time understanding and solving problems in moderately complex RC circuits... Please Help. You don't have to solve right up to the numerical value, that is not my priority, Rather If you could just explain how to begin and process through the question, It would be best...
  33. R

    First Order RC Circuit Analysis: Homework Equations and Attempted Solution

    Homework Statement Homework Equations vc(t) = vc(∞) + [vc(0+) - vc(∞)]*e-t/τ (Voltage in a driven RC circuit) τ = RC (time constant for an RC circuit) The Attempt at a Solution I'm pretty shaky with these sorts of problems and am quite unconfident of my work here. Step...
  34. S

    RC Circuits: Graph Homework - Determine Flash Frequency & Voltage Sketch

    Homework Statement A simple type of blinking light circuit can be constructed using a neon lamp. The circuit has a 4.0uF capacitor in parallel with a neon lamp. When the voltage is low in the RC portion of the circuit, the lamp does not conduct electricity. Therefore, it is effectively not...
  35. D

    RC Differentiator: What is Physically Happening?

    Hi guys, I have a quick question I think. Let's consider an RC differentiator driven by a 0-5V square wave which is initially at 0V. When the input voltage suddenly makes the transition to 5V one side of the capacitor will jump to 5V. I've read that the other side (side with the resisitor)...
  36. I

    Using Kirchhoff's rule in RC circuit while charging

    Hello I have a conceptual question about using Kirchhoff's voltage rule to derive expression of the charge in the RC series circuit when it is being charged by certain EMF. Usually most books start by writing the equation \mathscr{E}-iR-\frac{q}{C}=0 But when the charging is going on...
  37. D

    Lancaster Enjin Scaling for RC

    Building a RC Lancaster 1/10 Scale Planning on putting in 4 x 4stroke glow fuel enjins on it Expected weight is 10-20 kg - but have no real idea yet Any sugestions? Real Lanc is as follows - from Wikipedia of coarse Wingspan: 102*ft 0 in (31.09*m) Height: 20*ft 6 in (6.25*m) Wing...
  38. P

    Can the Impedance of Series RC and Parallel RL Circuits be Equal with Same R?

    Homework Statement Can a series RC circuit and a parallel RL circuit have the same impedance if the R is the same in both? What would the values of R, L and C have to be if they can? Why/why not, physically speaking? Homework Equations Zr=R Zc=1/iwC ZL=iwLThe Attempt at a Solution I know in...
  39. P

    Power in the components of an RC circuit as a Function of time

    Homework Statement A simple RC circuit with an EMF source ε, Resistor R and capacitor C are in series. When the switch is closed find the rate of energy stored in the capacitor, the power dissipated in the resistor, and the power supplied by the emf as functions of time. Homework Equations...
  40. P

    Multi-loop RC circuit, 2 batteries, 7 resistors, 1 capacitor

    Homework Statement For the multi-loop circuit as shown, assuming the capacitor is initially uncharged, find the currents in each of the resistors at t=0 after the switches are closed. So I believe there are 8 unknowns really because of the 8th branch with the capacitor. If you look at the...
  41. M

    Solve Charging RC Circuit: Find Capacitor Charge at t1

    Homework Statement Switch is initially opened with the capacitor uncharged. At t=0 the switch is clsoed. At time=t1 later, the potential difference between A and B is 2.00volts Find the charge on the capacitor at time t1. R=10,000ohms C=2.4nF Vb=12volts VA->B-=2.00volts Homework...
  42. K

    What is the Capacitance of a Charging RC Circuit with Known Time and Resistance?

    Homework Statement "A capacitor is being charged from a battery and through a resistor of 20kΩ. It is observed that the voltage on the capacitor rises from 10% of its final value to 90%, in 15 seconds. Calculate the capacitor's capacitance. t = 15s R = 20kΩ Vi = 10% of max Vf = 90% of max...
  43. M

    Time it takes for a RC circuit to fully charge

    Homework Statement How much time does an RC circuit require to become fully charged assuming that the capacitor was initially uncharged. resistance = R capacitance = C Voltage = V Homework Equations Q=CV(1-e^(-t/RC)The Attempt at a Solution so T = -ln(Q/(CV) - 1)RC but Q = 0 since it's...
  44. H

    Finding the Resistance in an RC Circuit

    Homework Statement A 10-µF capacitor is charged by a 10-V battery through a resistance R. The capacitor reaches a potential difference of 4 V in a period of 3 s after the charging began. Find the value of R.Homework Equations c=q/v q=CE(1-e^-t/RC) i=(E/R)e^(-t/RC)The Attempt at a Solution I...
  45. D

    Engineering Solving for voltage and current on an RC circuit

    Homework Statement Uploaded problem 5 Homework Equations i1=(R2/(R1+R2)) i2=(R1/(R1+R2)) The Attempt at a Solution Are my answers for problem 5 ok?
  46. M

    Understanding Voltage in Parallel RC Circuits

    Hello, I know that if two resistors are in parallel or two capacitors, they have the same voltage. However, is it the case that a resistor and capacitor in parallel also have equal voltage?
  47. B

    Electric Potential in RC Circuits

    Hello, At the moment, I am writing the theory portion of my lab report. In the RC circuit, will the electric potential across the capacitor be at the same electric potential as the battery? Or will it depend on the voltage drop across the intermediate resistor?
  48. G

    Electric Circuit Question - RC Circuit

    Homework Statement http://img163.imageshack.us/img163/6339/rccircuit.png Homework Equations The Attempt at a Solution I'm trying to find the node voltage. I was going to try and solve the problem knowing that the net charge is zero. Q = CV I'm having problems the voltage...
  49. T

    Finding charge of a capacitor in RC circuit

    Thanks, solved!
  50. P

    RC Time Constant in Piezoelectrics

    Hello, This is my first post so I hope I do everything correctly. I am required to calculate the RC time constant in piezoelectrics. I am trying to do this with data that I already have, Resistivity (not resistance) and Permittivity, and I no longer have the dimensions of the sample that I...
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