What is Rlc circuits: Definition and 50 Discussions

An RLC circuit is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel. The name of the circuit is derived from the letters that are used to denote the constituent components of this circuit, where the sequence of the components may vary from RLC.
The circuit forms a harmonic oscillator for current, and resonates in a similar way as an LC circuit. Introducing the resistor increases the decay of these oscillations, which is also known as damping. The resistor also reduces the peak resonant frequency. In ordinary conditions, some resistance is unavoidable even if a resistor is not specifically included as a component; an ideal, pure LC circuit exists only in the domain of superconductivity, a physical effect demonstrated to this point only at temperatures far below and/or pressures far above what are found naturally anywhere on the Earth's surface.
RLC circuits have many applications as oscillator circuits. Radio receivers and television sets use them for tuning to select a narrow frequency range from ambient radio waves. In this role, the circuit is often referred to as a tuned circuit. An RLC circuit can be used as a band-pass filter, band-stop filter, low-pass filter or high-pass filter. The tuning application, for instance, is an example of band-pass filtering. The RLC filter is described as a second-order circuit, meaning that any voltage or current in the circuit can be described by a second-order differential equation in circuit analysis.
The three circuit elements, R, L and C, can be combined in a number of different topologies. All three elements in series or all three elements in parallel are the simplest in concept and the most straightforward to analyse. There are, however, other arrangements, some with practical importance in real circuits. One issue often encountered is the need to take into account inductor resistance. Inductors are typically constructed from coils of wire, the resistance of which is not usually desirable, but it often has a significant effect on the circuit.

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  1. Butterfly41398

    Series RLC Circuits: Resonant Frequency of 60° at 40 Hz

    Summary:: About resonant frequencies A series RLC circuit with R = 250 ohms and L = 0.6 H results in a leading phase angle of 60° at a frequency of 40 Hz. At what frequency will the circuit resonate? Answer is 81.2 Hz but i got a different answer. May someone please correct me.
  2. H

    Understanding RLC Circuits: Series vs Parallel

    I'm a bit confused with RLC circuit. If in series, IL = IL, max * cos(wt) If in parallel, IL = - IL, max * cos(wt) Are these correct?
  3. E

    Impedances for RLC circuits in the limit of zero frequency

    If a voltage source is sinusoidal, then we can introduce a phasor map and come up with equations like$$V_0 e^{i \omega t} = I(R + i\omega L + \frac{1}{\omega C} i)$$where ##I## would also differ from ##V## by a complex phase. But if you set ##\omega = 0##, which would appear to correspond to...
  4. paulmdrdo

    Series RLC and Parallel RLC circuits

    Summary: Series RLC and Parallel RLC circuits How can the voltage across a capacitor or inductor in a series RLC circuit be greater than the applied AC source voltage? The formula suggest that either can be larger than the source voltage but I still find it counter intuitive. Also for...
  5. T

    Can a radio frequency be lowered by a passive circuit?

    Is it possible to design an unpowered antenna, (possibly some kind of RLC circuit) which will receive a radio wave at a particular frequency and then re-emit it at a lower frequency?
  6. W

    RLC Circuits - Q Factor and Amplitude

    Homework Statement Imagine you have two RLC circuits you are trying to scan for resonances. They have identical resonant frequencies, but circuit 1 has a very high Q-factor (Q1 >> 1), and circuit 2 has a very low Q-factor (Q2 < 1). Let's assume you are already on resonance and looking at V(out)...
  7. e0ne199

    Engineering Problem with series RLC circuit and dependent source

    Homework Statement here is my problem : Homework Equations like usual, the problem is related with RLC circuits and transients The Attempt at a Solution [/B] from here, the solution is obviously wrong because from the solution, its alpha should be -300 and not -0.4...and from the...
  8. J

    Trouble Understanding RLC Circuits: Detailed Explanation for 250W Power Release

    I'm having real trouble understanding some concepts in RLC circuits. If I have a circuit like this. The effective voltage is 120 V. What is the required frequency for resistor to release power of 250 W? I want to really understand this on a deeper level so please make the explanation...
  9. A

    RLC Circuits Problem: Find Frequency, Decay Time & Current

    Homework Statement A certain circuit has a resistance of 30 Ω, inductance of 5.0 mH, and capacitance of 0.375 µF. At time t=0, the capacitor is charged with 4.0 µC on the top plate (and -4.0 µC on the bottom), and the switch is then thrown so that the capacitor can discharge through the...
  10. Hassan Raafat

    Calculating Half Power Frequencies in RLC Circuits

    at electric circuits , at RLC circuits , in case resonance :why do we calculate the frequencies w1 & w2 at half power frequencies ?
  11. 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...
  12. R

    AC Homework: 10 Ohms Resistor, 12 uF Capacitor, 28 mH Inductor

    Homework Statement A 10 ohms resistor, a 12 microFarad capacitor and a 28 mH inductor are connected in series with a 170 V generator. A.) At what frequency is the rms current maximum? B.) What is the maximum value of the rms current? Homework Equations A.) Fo = 1 / 2pi sqrtLC b.) Irms = Vrms...
  13. B. Vane

    RCL Circuit: 2 Resistors, 1 Capacitor, 2 Inductors

    Homework Statement NOTE: Image uploaded with thread shows problem in clearest possible form. V = (45v)sin(80[pi] t) Resistors 1 and 2 = 50 Ohms Inductor 1 = 20 mH Inductor 2 = 2.5 mH Capacitor = 50 uF a) Find the power dissipated by each resistor. b) At what frequency will both resistors...
  14. B

    Differentiator/Integrator circuits: Op-amp vs RLC circuits

    It is possible to use a capacitor/inductor in an op-amp to allow it to perform the mathematical function of differentiating or integrating an input signal. It is also possible to do this without an op-amp, using simply resistors, inductors and/or capacitors. So what are the advantages of using...
  15. J

    Setting up an LRC series circuit with coupled coils

    Homework Statement I have been trying to set up an LRC series circuit where in place of an inductor we have a pair of coupled coils. My aim is to determine the resonant frequency in the circuit when the voltage across the resistor or the current in the circuit is at a maximum. I am using a...
  16. dwn

    Engineering What is the critical damping equation for this series RLC circuit with R = 1.5?

    Homework Statement Image Homework Equations Critical damping : e-αt(At + B) R = 1.5 The Attempt at a Solution I'd like to post this before anything else to make sure that I've analyzed the circuit correctly. t < 0: vc(0) = 9V , iL(0) = 9/4 = 2.25A i = e-t/3(At + B) i(0) = B = 2.25A...
  17. E

    Parallel RLC Circuits - Help please

    Homework Statement I'm working through this question, but on the final part I've hit a brick wall so I'd be grateful for any help please. The tuned circuit has a Q-factor of 1000 and is designed to resonate at 1MHz. At resonance, the supply current I is measured at 15μA for supply...
  18. S

    Capacitively coupled RLC circuits

    Homework Statement Given a set of two capacitively coupled RLC circuits where each has a capacitor C and they share a coupling capacitor C^{'}. I'm trying to find nice organized material that will explain the various relevant coefficients\concepts like QF, bandwidth etc. in relation to the...
  19. N

    Is there always a phase shift between current and voltage in an RLC circuit?

    Hey. Say you have an RLC circuit with an AC supply. Then I=ei(ωt-α). My question is: will α always exist, ie will the current always be phase-shifted compared to the voltage, as long as the impedance has an imaginary component or if the circuit is not at resonance? Does Z = |Z|*eiα, where α =...
  20. M

    What is the Frequency for In-Phase Current and Voltage in RLC Circuit?

    Homework Statement This was a part question and I got everything else but one part (#4!): 1) A 60-Hz generator with an RMS potential of 240 V is connected in series with a 3350 Ohm resistor and a 1.5 microFarad capacitor. What is the RMS current in the circuit? IRMS = 6.34 * 10-2 A...
  21. V

    Converting input in rlc circuits

    I was wondering how to convert E=70.7sinwt..<-- (just an example) to something like 50∠0 degrees?
  22. T

    What is bandwidth in the context of RLC circuits?

    Homework Statement I noticed that bandwidth is the difference between the frequencies that gives half power: But sometimes it is the difference between when the frequency is 0 and the frequency that gives half power: So the definition in my lecture slides states that bandwidth is the...
  23. R

    Multiple inductor or capacitor RLC circuits

    So I know that the equation for the natural frequency of an RLC circuit is: ω0=(LC)-1/2 I'm just wondering how this would change for a circuit with more than one inductor or capacitor. Say for instance an inductor in parallel with a capacitor, both connected in series to another inductor...
  24. R

    Multi inductor or capacitor RLC circuits

    So I know that the equation for the natural frequency of an RLC circuit is: ω0=(LC)-1/2 I'm just wondering how this would change for a circuit with more than one inductor or capacitor. Say for instance an inductor in parallel with a capacitor, both connected in series to another inductor...
  25. C

    Engineering Answer RLC Circuit Q Factor 70, 5V Supply at 2.5kHz

    A series RLC circuit is connected to a 5 V supply, the frequency of the supply is adjusted to give a maximum current of 11.9 mA at 2.5 kHz. The Q factor is 70. Determine the component values of the circuit. R= 5/.0119=420.2 Ohm Q = (1/R)*(sqrt L/C) 70 = (1/420.2)*(sqrt L/C) 70/(1/420.2)=...
  26. K

    Differential Equations RLC Circuits

    Homework Statement A series RLC circuit has an electromotive force given by E=200e^(-100t) V, a resistor of 80 ohms, an inductor of 0.2 H, and capacitor of 5x10^-6 F. If the initial current and charge on the capacitor are zero, find the current at any time t>0. Homework Equations ...
  27. K

    Understanding RLC Circuits: Calculating Current in a Series Circuit

    A series RLC circuit has an electromotive force given by E=200e^(-100t) V, a resistor of 80 ohms, an inductor of 0.2 H, and capacitor of 5x10^-6 F. If the initial current and charge on the capacitor are zero, find the current at any time t>0. How on Earth do i start this?!
  28. J

    Engineering Homework regarding getting the differential equations of the RLC circuits

    Homework Statement here is the circuit >>> http://www.4shared.com/photo/F3ewfm_3/22_online.html the whole question is here >>> http://www.4shared.com/document/Qwxgzq78/Circuits_for_Modeling.html whats assigned to me is #22. anyways, what we need to get here is the differential equations...
  29. S

    Questions about RLC circuits and OP amps

    Hi guys I really need some help to finish this on time, 1. A circuit with V volts and a 2 ohm resistor and a 2mH inductor and a 500uF capacitor in series. There is a graph of current through circuit over time, starting at 0 current icnreases to 20 amps in 1 mS stays there for 1 ms then goes...
  30. T

    Calculating Resonance Frequency and Amplitude in RLC Circuits

    Homework Statement I did an experiment using an RLC circuit (in series) and an oscilloscope to determine the resonance frequency and amplitude (in volts) of my components (R total = 2300ohm, L = 0.081H, C = 1.5E-8F). I plotted all the data I collected (V vs. f) and got a nice response curve...
  31. B

    How Does Phase Angle Affect Current in an Undriven RLC Circuit?

    Homework Statement I am given a RLC circuit in series with a fully charged C. There is no applied voltage at this part of the problem. Using kirchhoff I arrive at a second order diff.eq which leads me to the (correct) solution for the charge in the capacitor: q(t) = Q0exp(-t/T)cos(wt + Ø)...
  32. E

    Understanding Characteristics of RLC Circuits

    speaking of R-L-C series and parallel circuits, can anyone tell me what is the physical meaning of characteristic frequency, damping ratio, overdamped, underdamped, critically damped circuits?
  33. O

    RLC Circuit Problem: Finding Currents and Voltages Using Mesh Analysis

    Hello everybody, So I've been on this problem for nearly 4 hours now and am still blank at what i need to do as this book only has 2 RLC circuit examples that are not helping. --R1-----R2-- | | | Vs L C | | | ------------- (well...this diagram didn't...
  34. F

    RLC Circuits - Resonant Frequency, Power

    Homework Statement An AC circuit consists of an alternative emf of 1 V connected to a resistor of 500 Ohms, an inductance of 0.4 mH, and two capacitors connected in parallel of 50 pF each, We want to find the resonance frequency of this circuit, the maximum power dissipated by the...
  35. E

    RLC Circuit Resonance Frequency for WRUF Broadcast

    Homework Statement a) WRUF broadcasts at 103.7 MHz, what is the wavelength associated? b) If you were to use an RLC circuit to tune to this radio station, what resonance frequency would you tune to? Homework Equations f(resonance)= 1/(2\pi\sqrt{LC}) The Attempt at a Solution a)...
  36. G

    Engineering RLC Circuits: Determine i(0+), v(0+), i(∞), and v(∞)

    http://image.cramster.com/answer-board/image/501adeb46c35e1d66d704eb5d3c30ced.jpg 1) Determine: a. The value of i(0+) b. The value of v(0+) c. The value of i( ∞) d. The value of v( ∞) 2) For t > 0, determine: a...
  37. R

    Solving RLC Circuits: Using Thevenin, Norton, etc.

    hey everybody!...sorry for the stupid question...Can you use Thevenin, Norton, superposition and Node analisys in RLC circuits?...if so...could you pass some examples circuits?...Thanks!
  38. B

    Archived Series RLC Circuits: Calculate VL, VC, VR & Phase Angle Phi

    Homework Statement A series RLC circuit has a 0.19 mF capacitor, a 16 mH inductor, and a 10.0 resistor, and is connected to an ac source with amplitude 9.0 V and frequency 60 Hz. (a) Calculate the voltage amplitudes VL, VC, VR, and the phase angle phi . VL = V VC = V VR = V...
  39. A

    Solve Series RLC Circuit: Kirchhoff's Loop Rule

    Given a series RLC Circuit driven by a generator, Kirchhoff's Loop Rule gives: V_{peak} cos \omega t - L\frac{di}{dt} - IR - \frac{Q}{C} = 0 - OR - V_{peak} cos \omega t = L\frac{d^{2}Q}{dt^{2}} + \frac{dQ}{dt}R + \frac{Q}{C} I have never done second order differential equations, so...
  40. K

    RLC Circuits: Current from Emf at Very Large/Small Freq.

    Homework Statement What is the current supplied by the emf when the frequency is very large and very small? ------------------------- | | | ------------------------ | | | |...
  41. P

    Energy of fields caused by RLC circuits

    I am looking for simple animations of RLC circuits, energy of RLC circuits and vaves they cause; if anyone have them please send to pasvvords@yahoo.com
  42. Cyrus

    Homework on RC, RL and RLC circuits

    In light of all the threads started in here about people who BMC about flunking tests, I will post the opposite. I had my thermo test today. It was hard in my opinion. But I think I got a 12/12 on it :cool:. I studied 4 days for, I better get a 12! I need to lower the entropy in my life...
  43. F

    Solving RLC Circuits: Lamp Glowing & Tuning a 100MHz Circuit

    Hi I have two probles to tackle on RLC circuits The first states that if a circuit consists of a lamp (R), variable inductance and fixed capacitor, why does the lamp glow for certain values of L. Also, you have a tuner at 100mhz, the resistance in the circuit is 15 ohms and inductance...
  44. D

    Exploring RLC Circuits: Lamp Brightness & Inductive Reactance

    :cry: hi i got 2 questions here fairly confusing was wondering if i can get some help thanks 1. consider a series RLC circuit in which R is an incandescent Lamp C is some fixed capacitor and L is a variable inductance. The source is 240 V ac. explain why the lamp glows brightly for some...
  45. J

    Engineering Calculating Frequency in RLC Circuits with Gradual Decay

    Oscillation frequency I'm not sure what to do for this question. I have found a few things of relevancy but I'm making the problem more complex than it really is? A leyden jar of capacitance C=10^-9 farads is short circuited with a copper wire of self-inductance L=3 x 10^-7 and resistance...
  46. S

    Phasor Diagrams of Series Parallel RLC circuits

    Hi Guys! well! can anybody tell me the correct way of drawing phasor diagrams of Series-Parallel RLC circuits. I know how to draw for Series RLC and Parallel RLC but don't know WHEN it comes to SERIES-PARALLEL combined. Plz help me. Plus can u recommend me any website from where i can...
  47. D

    Solving RLC Circuit with 2 500pF Capacitors and 80mH Inductor

    Hey ive got a problem with a series rlc circuit it has 2 500pF capacitors and 1 80mh Inductor and one 2.0K ohm resistor circuit has a freqency of 55 KHZ trying to calculate total impedance I am getting the wrong answer im getting: Xc= 1.93 kohms Xl = 27.6 kohms xl-xc = 25.7...
  48. A

    Question about RLC circuits

    A person is working near the secondary of a transformer, as shown in the figure below. The primary voltage is 120 V at 60.0 Hz. The capacitance C, which is the stray capacitance between the hand and the secondary winding, is 10.0 pF. Assuming that the person has a body resistance to ground R...
  49. F

    What Happens to Voltage in a Parallel LRC Circuit with a DC Source?

    quick question about RLC circuits... Okay guys and gals... I know this is a rather dumb question, but I don't have a lot of reference material where I am at currently (I am in Kuwait as part of Operation Iraqi Fredom)...so if someone could give me an answer I would appreciate it... I...