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. M

    Current and Time in RL Circuit

    Homework Statement An emf of 10V is connected to the RL circuit (R = 10 Ohms, L = 1.0 H) shown below for long, long time (the switch is in position 1). Then, at t = 0 the switch is thrown into position 2. Find the current in the circuit at t = 0.2 s. When will the current drop to 0.001 A...
  2. I

    RL Circuit Differential equation

    Homework Statement Basically, I am deriving the following equation: I=I_0(1-e^{-\frac{R}{L}t}) Homework Equations 1) L\frac{dI(t)}{dt}+I(t)R=V 2) \frac{V}{R}=I_0 The Attempt at a Solution In relevant equation 1), R was divided both sides, and by using 2), I turned it into...
  3. W

    RL Circuit: Kirchoff's Law is Wrong - Faraday's Law is Correct

    Hi Guys, This is going to be a bit controversial but that's ok. In an RL circuit, both with and without a battery, Kirchoff's law is invoked in virtually every elementary textbook in the United States and perhaps in the world. It is a mistake! The voltage drop across an inductor is...
  4. S

    How Do You Calculate Time-Dependent Current in an RL Circuit?

    Using Kirchhoff's rules for the instantaneous currents and voltages in the two-loop circuit, find the current in the inductor as a function of time. I used Kirchhoff's rule on the left loop consisting of the battery and the right loop which consist of the inductor and gotten the following...
  5. N

    Calculating Resistance and Input Voltage in an RL Circuit with AC Generator

    Homework Statement A resistance R and a 1.4 H inductance are in series across a 60 Hz AC voltage. The voltage across the resistor is 30V and the voltage across the inductor is 40V. (a). What is the resistance R ? (b). What is the AC input voltage ? Homework Equations \xi=I*Z The Attempt at...
  6. M

    Analysis of an RL Circuit: Voltage, Current and Time Dependence

    I am trying to analyse an RL circuit, particulartly the dependence of current in 2 resistors with time, in an RL circuit. This is what I think but I would really love some people to tell me if I am getting it wrong or if there is anything they want to add to it. ***Just after the the switched...
  7. M

    Engineering Need help on solving a RL circuit with switch

    Homework Statement Homework Equations Find v(t) for t < 0 and t > 0 in the circuit. The Attempt at a Solution I tried to find the i through the inductor for both t=0- and t=infinity, but I did not get the same result as the answer given in the txtbook which is 96e-4t V. According...
  8. N

    Calculating Inductance in an RL Circuit

    Homework Statement An RL circuit has a 9.0 V battery and a 5.5 ohm resistor. When the switch is closed, the current in the circuit is observed to increase from 0 to 0.30 A in 0.17 s. A) What is the inductance? B) How long after the switch is closed does the current have the value 0.47 A...
  9. K

    Solve RL Circuit Homework: KVL, Voltage, Current, Time

    Homework Statement The switch has been closed for a long time. a) Current flowing through inductor. Voltage across it. IS any current flowing through the resistor. b) The switch opens at t = 0s. Find an equation for the inductor voltage as a function of time for t > 0. How long does it take...
  10. M

    Engineering First-order RL Circuit analysis

    Homework Statement Homework Equations I am not really sure which equations would be relevant since my question seems to be more so concepts instead of numbers, so forgive me please :( I am familiar with how to do just about all of this problem, I am simply baffled as to how I handle the...
  11. E

    Why is the Time Constant Used in Solving Inductance Problems?

    This is not a homework problem, but practice. I have the answer. I need to know why. Homework Statement Homework Equations i=\frac{E}{R}(1-e^{\frac{-t}{\tau}}) "charging" an Inductor The Attempt at a Solution I have solved part a) correctly...
  12. X

    What Determines Maximum Voltage in an RL Circuit with AC Power?

    I know this is a simple question but I can't quite figure out how to do this in a combined circuit: Find the maximum voltage across a resistor R and inductor L with an AC power source of V0sin(wt). (Note: the resistor is in series with the inductor) I'm trying to figure out the total max...
  13. X

    RL Circuit Discharge and RCL Circuit

    In the RL Circuit Discharge and RCL Circuit, if you had only measured the resistance of your resistor and not taken into account the resistances in the inductor and function generator, how would this affect the calculated inducted from the half life measurement?
  14. X

    Finding the Inductor in an RL Circuit

    Homework Statement I'm trying to find the inductor RL Circuit: Resistor (22Ω), Inductor , Function Generator Resistance (Ω): 24.7 Ω 50 RL Circuit Half-Life: 64.00µs RLC Circuit, Resonance: Resistor (1000Ω), Inductor , Function Generator...
  15. Q

    Engineering Help with home work question, RL circuit

    vf= 4(u(t)-u(t-1.8))v I have to find i(t), for the attached circuit. I already evaluated it for t<0. But i a having problems in the rage 0<t<1.8. I am at the point where i have to find the forced response, so o let t tend to infinity (t->infinity). And so the Inductor acts like a short...
  16. S

    Differential EQ of this RL Circuit

    Hi, I have the above the circuit and I've ended up with the following differential equation. I've tried solving it by separating the variables, but am not sure if its the right answer. IR + L(di/dt) + IR = x(t) x(t) = 5V. But since IR = y(t) and di/dt = 1/R dy/dt. y(t) is the...
  17. A

    Engineering High Pass Filter RL circuit: Time/Frequency Response

    Homework Statement For circuit B on page 2, find: a) the time domain response v0 for a unit step input b) input/output transfer function T(s) = v0/v_in c) plot v0 vs. time d) plot sinusoidal steady state vs. frequency: the magnitude in dB and phase in degrees of T(s) Homework...
  18. I

    Partial RL Circuit: Solving for Current in Inductor with Kirchhoff's Rules

    Homework Statement A current pulse is fed to the partial circuit shown in Figure P32.25. The current begins at zero, then becomes Imax = 7.0 A between t = 0 and t = 200 µs, and then is zero once again. Determine the current in the inductor as a function of time. Let L = 1.0 mH and R = 100 ...
  19. W

    Engineering Understanding a Simple RL Circuit | GRE Physics Problem Explanation

    Homework Statement The problem is from an old GRE that I can't wrap my head around. http://grephysics.net/ans/8677/94 Homework Equations V = -L(dI/dt) I = V/R The Attempt at a Solution Okay, so I have the solution, I just don't understand their reasoning. A change in current...
  20. S

    Engineering Finding i(t) (Source Free RL Circuit)

    1. http://img529.imageshack.us/img529/6205/87421877rv5.jpg [/URL]3. First I found i(0) the equation for a source free RL circuit is i(t) = i(0)e^(-t)/T T = L/ReqSince the inductor will be shorted when t<0, i(0) must be 5mA. Now to find Req I added series and parallel appropriately to find...
  21. G

    How Do You Calculate Different Parameters in an RL Circuit?

    An RL circuit in which L = 9.00 H and R = 5.00 is connected to a 24.0 V battery at t = 0. (a) What energy is stored in the inductor when the current is 0.500 A? (b) At what rate is energy being stored in the inductor when I = 1.00 A? (c) What power is being delivered to the circuit by the...
  22. G

    How do you calculate inductance in an RL circuit?

    [SOLVED] Inductance RL Circuit Calculate the inductance in an RL circuit in which R = 0.300 and the current increases to one fourth its final value in 1.40 s. I tried doing this with V=IR, (I know, the easy way didn't work). I also tried I= V/R(1-e^(Rt/L)) but I don't know what V would...
  23. M

    Engineering Understanding Basic Applications of RL Circuits

    Can someone explain to me 2 basic applications of RL circuits? What are they used for and some examples, please. I'm quite confused. It doesn't take much.:blushing:
  24. A

    Engineering Solve RL Circuit Power Problem:V source 140V, 33A load, X=5R, Vload 115V, 3kW

    An AC source of 140V feeds 33A to a load, though a cable represented by an unknown resistance R in series with an unknown inductive reactance X. The manufacturer of that cable says, in the catalog, that X=5R. The voltage at the load is 115V. The power supplied by the source is measured...
  25. K

    Simple RL Circuit: Verifying Current Flow After Switch Opened

    I posted this is the homework section, but it looks like EE homework problems are getting more attention here. I'm pretty sure I've got this right, but I would like to make sure before I hand this is. V=10V DC source I1 = 1H inductor I2 = 2H inductor R = Resistor S= a switch that has...
  26. K

    Engineering Solve Simple RL Circuit: Find and Sketch y(t)

    Homework Statement The switch is closed for a long time and opened instantaneously at t=0. Find and sketch the current y(t). I haven’t had a class where I needed to do DC transient circuit analysis for over a year, so this simple thing is giving me some problems. The way I see it...
  27. A

    Engineering 1 V source, 1 I source, RL circuit, find power

    Homework Statement Hey guys, this is a question from one of the past exams. I've got my exams coming up and I was looking at this question, and I couldn't figure out how to start. I initially used KVL, but I then got two unknowns, the Voltage of the current source and the current of the...
  28. S

    Struggling with Solving an RL Circuit Differential Equation?

    Hi guys, I'm currently deriving all the equations provided by the my physics professor on the RL, RC and LCR circuits. My trouble is not the physics but the mathematics. For example in the RL circuit the differential equation that needs to be solved is the following: L\frac{dI}{dt} +IR =...
  29. C

    Finding Initial Current and Natural Response in an RL Circuit

    Can anyone please help me slove this example circuit i found. im having a hard time finding the initial current through the inductor and duno how to deal with the dependent source and inductor after the switch is opened.
  30. P

    Calculating Time for Inductor Voltage to Drop to 13 V in RL Circuit

    One application of an RL circuit is the generation of time varying high-voltage from a low-voltage source as shown in the figure. 1257 ohms 14 ohms 2 H (switch) b...
  31. M

    RL circuit fun am I drawing this circuit correct at different times?

    Hello eveeryone! exam time monday! Just doing some last checks to make sure I'm understanding this correctly. Here is the directions and circuit: THe circuit shown below has beeen in the form shown for a very long time. THe switchopens at t =0. FInd iR at t equal to (a)0-, (b) 0+, (c)...
  32. M

    Driven RL circuit, why at infinity is this the current 2, and yet at 0+, its 0?

    Hello everyone I'm confused...i was just doing RL and RC circuits without a driven source, they made sense after doing them a few 100 times. Now I'm at Driven RL circuits. My professor said: iL(infinity) = 2mA iL(0+) = 0. From my understanding, i thought at infinity, the switch has been...
  33. M

    Source free RL circuit confusion When this switch closes, does the current end?

    Hello everyone. I'm getting confused on what my professor did. Everything else makes sense to me but this one part. THe directions say: Aftering having been closed for a long time, the switch in the circuit is opened at t= 0. (a) find IL(t) for t>0, (b) Evaluate IL(10ms). I got both parts...
  34. P

    How Do You Calculate the Time Constant of an RL Circuit?

    Can anyone tell me what formula I would use to find the time constant for a circuit that reaches 85% of its final value 1.86 seconds after the switch is closed.
  35. G

    MATLAB Solving a RL Circuit Using MATLAB ode45

    I have analysed a RL circuit with freewheelind diode, switch and additional source. I have used ode solver which is called ode45 in matlab. This expression is [t, i]=ode45('inducwithE', tspan, i0'). There is three stages in that circuit and every last 'i' (current-this is the state variable)...
  36. N

    Parallel RL Circuit: Get Help with AC Supply & Differential Equation

    Hi there, Can someone help me with parallel RL circuit across ac supply?wats the differential equation ... Thanx for all help. ng
  37. A

    Maximizing Power Efficiency: Solving for Power Factor in RL Circuit

    Suppose you manage a factory that uses many electric motors. The motors create a large inductive load to the electric power line, as well as a resistive load. The electric company builds an extra-heavy distribution line to supply you with a component of current that is 90 degrees out of phase...
  38. K

    Back emf and battery emf in RL Circuit

    hello all!:smile: I have a question about electromagnetism. The question is "Can the back emf ever be greater than the battery emf in RL circuit?" can someone explain this one for me please?
  39. D

    RL Circuit with Two Loops: Solving for Current and Switch Equation

    I have a homework problem with an RL circuit. There are two loops in the circuit. One has the emf and two resistors and a switch and the other has two resistors and an inductor. The resistors, the inductor and the emf are all given values and I'm given that the switch is closed at time = 0...
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