What is Rl circuit: Definition and 139 Discussions

A resistor–inductor circuit (RL circuit), or RL filter or RL network, is an electric circuit composed of resistors and inductors driven by a voltage or current source. A first-order RL circuit is composed of one resistor and one inductor and is the simplest type of RL circuit.
A first order RL circuit is one of the simplest analogue infinite impulse response electronic filters. It consists of a resistor and an inductor, either in series driven by a voltage source or in parallel driven by a current source.

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  1. G

    Engineering AC Circuit (RL) Homework: Finding the Series R-L Equivalent for Two Loads

    Homework Statement In the circuit shown in Figure Q2(b), two loads A and B are connected to the source. The cable connecting the power supply to the load is modeled as series R and L of values R = 0.1Ω, L = 0.1 mH as shown in the figure. The loads have the following specifications...
  2. J

    Series R-L Circuit - Charge/Discharge described properly?

    Hi Rather than ask how it works iv'e studied this a bit (via conflicting sources) and hoping that another member could have a quick scan over and pick out any bits where I've got it wrong? I know its a lot to read, but iv'e tried to keep it as short as possible, so if you could help i'd be...
  3. I

    Engineering Finding Resistance in an RL Circuit for Time Constant Calculation

    Homework Statement Homework Equations τ = L/R The Attempt at a Solution So I already know the initial current and final current (-4mA and -1mA, respectively), my question is how I would find the resistance value to use to solve for the time constant. After the switch has been closed for a...
  4. R

    Engineering Energy Dissipation by Inductor (RL circuit)

    Homework Statement Homework Equations The voltage across an inductor is V(T) = L i' Basic current division and voltage division . Step function where u(T) : when t is smaller than 0 : u(t) = 0 t >0 : u(t) = 1 The Attempt at a Solution The voltage source has...
  5. I

    Engineering RL Circuit Charging: The Effects of Closing the Switch on Inductor Charge

    What happens when the switch closes? Does the inductor continue to charge? If yes, how can this be so when the inductor is already fully charged (the question says the switch was open for a long time, so I assumed it has been fully charged)?
  6. dwn

    Engineering Solve Driven RL Circuit: Understand KCL & Initial Current

    Homework Statement Image Homework Equations KCL DRIVEN RL CIRCUIT The Attempt at a Solution I got the right answer after trying a different tactic, but I don't understand why it is done this way. My first approach: KCL: 100/45 + 60/2 = iL for t < 0 32.22 -...
  7. dwn

    Engineering RL Circuit with current source

    Homework Statement Image Homework Equations Current divider The Attempt at a Solution The only thing I see is that I solve for R1 and R2 for t < 0. Other than that I'm confused and not even sure I'm right about solving t<0.
  8. P

    Power dissipated in an RL circuit

    Homework Statement a) A circuit contains two elements, but it is not known if they are L, R or C. The current in this circuit when connected to a 2.16×102 V, 60.0 Hz source is 6.10 A and lags the voltage by 3.60×10^1 degrees. What are the two elements? c) What is the power dissipated in...
  9. R

    Find resistance, inductance, and the time constant for an RL circuit.

    Homework Statement A 5.0V battery is attached to an RL circuit. The current is given by the formula: I = V0/R(1-e-t/τ), where I0 is the steady-state current, and τ is the time constant for the circuit. Using the data table provided, determine τ, R, and L for this circuit. I(mA) | t(μs)...
  10. V

    Engineering Finding the step response of RL circuit

    Homework Statement Homework Equations The Attempt at a Solution I understand everything except how they got i(∞). It seems like they used current division on 3A. But where are they applying current division and where did they get 3A? Also, in the last step, they magically added u(t). Where...
  11. V

    Engineering Finding Voltage in Series RL Circuit

    Homework Statement Homework Equations The Attempt at a Solution This assigned question is an odd one since it doesn't seem to have anything to do with phasors which is the chapter I am currently studying. I have this solution: I don't understand where they got that...
  12. D

    Engineering Solving RL Circuit Differential Equation: Initial Conditions

    Homework Statement Consider the RL circuit shown in the figure. Assume that the current ##i(t)## has reached a steady state with the switch at position ##A##. At time ##t = 0##, the switch is moved from position ##A## to position ##B##. http://imgur.com/dRIOrp0 If I use the image button...
  13. T

    Engineering Current in RL Circuit: Solving for Time-Dependent Current

    Homework Statement The circuit is in steady state before the switch is closed at t=0 I need to find how the current changes with time after the switch is closed. The Attempt at a Solution I read that at steady state inductor behaves like a short circuit, so does this mean when the switch...
  14. C

    Engineering Transient response of RL Circuit

    Homework Statement Find the expression of the current "i" by terms of time. The answer is 3e^(20t) Amps Homework Equations i(t)=I_final+(I_initial-I_final)*e^(-t/τ) The Attempt at a Solution I have found the initial current as 3 amps. However, after the switch had been changed for too long...
  15. G

    Differential Difficulties in an RL Circuit Problem

    Homework Statement An inductor with L = 50 mH is in series with a resistor of R = 180 ohms. At t = 0, a potential difference of 45 V is suddenly applied across the series circuit. At what rate is the current increasing after 1.2 milliseconds? Homework Equations V = IR + Emf Emf =...
  16. dwn

    What Is the Rate of Change of Current in an RL Circuit?

    Question 1 Homework Statement For a circuit show on Fig B1, what is the rate of change of the current in the inductor when the total current in the circuit is 0.50 A? (L = 10 mH, R(1) = 10 ohm, R(2) = 20 ohm, V = 12 V). In the figure the resistors of the circuit are in series. Ans: 200...
  17. E

    Engineering Two commutation processes for RL circuit

    Homework Statement I have to calculate first commutation process (t=0) and second commutation process (t1 = 2*τ) Both swithes are closing in the given time moment. Homework Equations Form of second commutation process: The Attempt at a Solution I have already calculated...
  18. E

    Engineering Two commutation processes for RL circuit.

    Homework Statement I have to calculate first commutation process (t=0) and second commutation process (t = 2*τ) Both swithes are closing in the given time moment as I wrote before. Homework Equations The Attempt at a Solution I'll do this task step by step, that's why here...
  19. N

    How can I control the current in an RL circuit using state space modeling?

    Hi.. This is sundaram, I'm trying to learn state space modeling, I'm trying to model the simple RL series circuit, to control/read the current flowing through inductor. I could find the way to monitor the voltage across inductor. as below x'=(u - Rx)*(1/L) y=(u - Rx) where: x => i...
  20. LADransfield

    DC Transient RL Circuit - Current Decay

    If I have a circuit with R = 1Ω L = 300μH V = 20V i0 = 5A I know that I can use the equation at the bottom of page 13 to calculate the current rise given any starting current and input voltage: i(t) = (V/R)[1-e-t/τ] + i0e-t/τ This is fine, and stops increasing at 20A as expected...
  21. E

    Engineering RL circuit differential equations

    Homework Statement Task is to write differential equation for this circuit. E, R1, R2, R3, L are constants. Homework Equations Ul = L di/dt The Attempt at a Solution I guess, we have to use current method for each contour. 1st contour equation: E = U1 + U2 + Ul =...
  22. N

    Calculating Total Current in a Parallel RL Circuit

    Homework Statement There's a DC supplying a current V over resistance R and inductor L in parallel. The circuit looks like this except it's DC http://sub.allaboutcircuits.com/images/02262.png I need to find the total current. The Attempt at a Solution I know that the current through the...
  23. M

    RL Circuit Analysis: Comparing Resistor and Coil Voltages

    Homework Statement At the moment t = 0, a 24.0-V battery is connected to a 5.00-mH coil and a 6.00-V resistor. (a) Immediately thereafter, how does the potential difference across the resistor compare to the emf across the coil? (b) Answer the same question about the circuit several seconds...
  24. skate_nerd

    RL circuit inductive reactance problem

    Homework Statement There's a coil, resistance R=7Ω, and inductance L=1mH, and its powered by a generator with variable frequency and Vmax=10V. At what frequency is inductive reactance equal to resistance? (when z=R√2) Homework Equations z=R√2, z=√(R2+(ωL)2) The Attempt at a...
  25. S

    Why does current decay in an RL circuit?

    I fully understand mathematically using differential equations and also using conservation of energy why current should decay in an RL circuit. However , I cannot comprehend how this phenomenon can be explained purely based on induced voltages and currents. An intuitive understanding basically...
  26. J

    Engineering Calculating when voltage across resistor = voltage across inductor in an RL circuit

    Homework Statement A step input of 100V is applied to a resistor of 50Ω in series with an inductor of 10H at time t=0. Calculate the time at which the voltage across the resistor equals the voltage across the inductor Homework Equations Im not sure which equation to use, i know τ=L/R...
  27. B

    The current in a series RL circuit

    Homework Statement The current in a series RL circuit increases to 20% of its final value in 3.4μs. If L = 2.0mH, what is the resistance R? Homework Equations I=I_0(1-e^(-t/(L/R))) <----Im not sure if this equation is right? The Attempt at a Solution I'm unsure how to start...
  28. H

    Engineering What is the power factor of an RL circuit with given parameters?

    Homework Statement See attachment. Homework Equations V(t) = Vmcos(\omegat + \theta) P(t) = VmImcos(\omegat + \phi)cos\omegat PR(t) = \frac{V^{2}(t)}{R} PF = \frac{P}{VeffIeff} S = VeffIeff Pavg = Ieff2(Re(Zeq) The Attempt at a Solution (a) Ieff = 5 A f = 50 Hz or \omega \approx 314 rad/s...
  29. B

    Engineering Is it possible to solve for VL in this parallel RL circuit?

    Homework Statement I have the following parallel RC circuit. At time T = 0, the switch will close and the circuit will be connected. We assume that prior to T = 0, the circuit was at a steady-state. I want to calculate VL(t) -- but I am being told that this is not possible for this...
  30. A

    Solve RL Circuit Equation: Kirchhoff's Rule Explained

    Suppose a circuit with resistor R and inductor L with no source. I am trying to find kirchhoffs equation for this circuit - I am getting iR -Ldi/dt = 0 as my equation which is apparently wrong. I just cannot understand how do I make equations for such circuits.
  31. S

    RL circuit time constant question

    Hi, Was hoping someone could help me. I have the following RL circuit: 20V input 8.2kohm resistor and 50mH Inductor in series. Determine time constant: I answered with: T = L/R 50mH / 8.2kohm = 6.09 uS Is this correct? The question I am stuck on is: Determine the...
  32. R

    Engineering Solving Impulse Response of RL Circuit

    Hi all, I'm taking a fourth year time-series analysis course for Physics students. Homework Statement Let us consider a simple physical system consisting of a resistor (with resistance R) and an inductor (with inductance L) in series. We apply an input voltage a(t) across the pair in...
  33. R

    Solving a Simple RL Circuit: Find My Fault!

    Homework Statement The Attempt at a Solution V-R_1I_1-LdI_L/dt=0, V-R_1I_1-R_2I_2=0, I_1=I_L+I_2 My result is I_L=(V/R_1)(1-exp[-tR_1R_2/(R_1+R_2)L]) Where is my fault? Any help is appreciated!
  34. Y

    Calculating inductance using a RL circuit and a frequency generator

    any help would be much appreciated i am trying to calculate the inductance and impedance of a unknown air cored inductor. over a set frequency range (1600hz - 2700hz in 100hz increments) using a series RL circuit tools scope multimeter frequence generator Amplifier 1ohm 100W metal...
  35. G

    Engineering Solve Part (a) Simple RL Circuit Problem

    I'm stuck at part (a) of this question: http://i.imgur.com/9IqKu.png It seems that the source is DC voltage, and since the inductor acts as a short circuit in DC, Vo is basically 1000V? So the sketch is basically a straight line? Is there something I'm missing here?
  36. G

    Engineering How Long Does It Take for Current to Reach Maximum in an RL Circuit?

    Hello I have the following calculations to do. An inductor of 10H and 25 ohm resistance is connected in series with a 75 ohm resistor and Vs=240 V DC. 1. the time for current to develop maximum current. so what I did is that: Max current is I= V/R= 240/(25+75)= 2.4 A And time constant T= 0.1 s...
  37. S

    What Happens to Current Direction in an RL Circuit When the Switch is Opened?

    Homework Statement A circuit made with a battery, a switch, an inductor. and three resistors is shown in the figure. To begin with, switch S has been open for a long time. Then at time t = 0 the switch is closed. http://i.imgur.com/ws5UD.png After being closed for a long time, the...
  38. S

    How Does Energy Increase in an RL Circuit with Time-Varying Current?

    Homework Statement An inductor initially has 3 A of current passing through it at time t = 0. The current through the inductor increases at a constant rate until 5 A of current is flowing through it 1s later at t = 1 s. The voltage across the inductor is 4 μV while the current is increasing...
  39. S

    RL circuit with three resistors

    Homework Statement http://i.imgur.com/22jq3.png Three identical resistors are connected to a battery, an inductor, and a switch as shown in the figure. (The values of all circuit elements are given below the figure.) The switch has been open for a very long time, and then it is closed...
  40. M

    Solve RL Circuit Problem: V, I, P, w, w(0)

    Homework Statement [PLAIN]http://img14.imageshack.us/img14/4355/screenshot20110807at249.png Homework Equations v(t) = Vmax * e^(-Rt/L) i(t) = imax * e^(-Rt/L) P = V^2/R w = integral of power w/ respect to time w(0) = .5Li^2(0) = energy stored in inductor The Attempt at a...
  41. S

    Calculating Phase Angle & Voltage in Series RL Circuit

    An inductor “L” is connected in series with a Resistor “R”. This circuit is connected to a sinusoidal voltage “V”, and a current of 1A flows. If the circuit resistor has a value of 1W, and the magnitude of the reactance of the inductor “L” is 1W at the supply frequency, state: (i) The...
  42. F

    Engineering Finding ZL for a series-parallel RL circuit

    Im starting to give up on this one, every time i try to figure it out i get an answer that is miles off. Im looking to find ZL, can someone show me how this is done? I think my problem is with the dependent voltage. http://img31.imageshack.us/i/unledak.png/
  43. S

    Complex impendance in RL circuit

    Homework Statement I have to show that the impendance of a parallel RL circuit would be the same in measure as the impendance of a non-parallel RL circuit (sry, don't know how to express this in English). I have to show this so that the inductivity stays the same in both cases but the...
  44. M

    Engineering Current through an Inductor in an RL circuit

    Homework Statement Find i0(t) see attached pictureHomework Equations io(t) = iinfinite + (i0- - iinfinite)e-Rt/L The Attempt at a Solution I first re-drew the diagram for when the switch has NOT been closed, which is esssentially the same thing without the 37.5 V Source and the adjacent 10...
  45. H

    Inductors & AC Circuits (Homework) (RL Circuit)

    Homework Statement What is the inductance in a series RL circuit in which R = 7.0 kΩ if the current increases to one half of its final value in 26 µs? Homework Equations am i correct in assuming that i should be using the time constant equation: Tau=L/R The Attempt at a Solution...
  46. C

    Engineering Help solving First Order RL circuit

    http://img713.imageshack.us/i/39642770.jpg At time t = 0_ The circuit looks like the voltage source in series with R1 and R2 with the inductor acting like a short circuit. iL (0_) = 60V/50Ω = 1.2A At t = 0+ The circuit looks like http://img839.imageshack.us/i/52735488.jpg...
  47. B

    Engineering RL Circuit - Problem finding Unknown Inductor

    Here is the circuit: http://img840.imageshack.us/f/60205514.png/ I need to find: I Z VL - Voltage on Inductor XL L I have I and Z but I can not figure out VL, XL, and L. This is what I have for I and Z: ----------------------------------------------- a.)...
  48. H

    How Does Switching Impact Current Flow in an RL Circuit?

    1.http://s1191.photobucket.com/albums/z462/havoc0040/?action=view&current=21prob42.jpg The switch in the figure is open for a very long time and then closed at t = 0. What is the current through R1 immediately after the switch is closed? ( Use V = 3.5 V, R1 = 848 , R2 = 548 , L = 7.2 mH )...
  49. E

    Engineering Total Impedance of RL Circuit in Parallel with Resistor

    Homework Statement find total impedance of a circuit with R1 and L in parallel with R2. circuit looks like this (but with R2 instead of C): http://wpcontent.answcdn.com/wikipedia/en/thumb/7/75/RL_series_C_parallel.svg/160px-RL_series_C_parallel.svg.png Homework Equations formula for two...
  50. P

    Engineering Solving Current in RL Circuit: Find i(t=6s)

    Homework Statement The voltage v(t) shown in the circuit attached ("Circuit 8.3") is 10 V for the time 0<t<2 (s), -10 V for the time 2<t<5 (s), and 0 all other times. If iL(0) = 0, what is i(t=6s)? Homework Equations i(t) = i(t=infinity) + (i(to)-i(t=infinity))*exp(-(t-to)/\tau) {1}...
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