What is Lc circuit: Definition and 104 Discussions
An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuit's resonant frequency.
LC circuits are used either for generating signals at a particular frequency, or picking out a signal at a particular frequency from a more complex signal; this function is called a bandpass filter. They are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers.
An LC circuit is an idealized model since it assumes there is no dissipation of energy due to resistance. Any practical implementation of an LC circuit will always include loss resulting from small but non-zero resistance within the components and connecting wires. The purpose of an LC circuit is usually to oscillate with minimal damping, so the resistance is made as low as possible. While no practical circuit is without losses, it is nonetheless instructive to study this ideal form of the circuit to gain understanding and physical intuition. For a circuit model incorporating resistance, see RLC circuit.
In a simple LC circuit,
How do i set up the differential equation?
Following Walter Lewin's teaching that
0) Use Maxwell-Faraday Equation instead of Kirchhoff Rule
1) if E field and dl are in the same direction, then I write a positive term.
2) There is no electric field in an...
Hello Everyone,
I am making an LRC circuit by having a Coil attached to a Capacitor attached to a Light-bulb which is attached to the Coil. Provided that the radio signal (of 2000 Mhz) I'm trying to "collect" is strong enough and the coil/capacitor is properly tuned I should see the...
Hi all,
I am currently building up a lightning detector based on this website: http://www.techlib.com/electronics/lightningnew.htm
as the diagrams shows, the resonance tank included a 10mH inductor and a 10pF capacitor.
As I want to calculate the resonant frequency (using the formula f =...
Homework Statement
A circuit is constructed with a resistor, two inductors, one capacitor, one battery and a switch as shown. The value of the resistance is R1 = 481 Ω. The values for the inductances are: L1 = 281 mH and L2 = 163 mH. The capacitance is C = 85 μF and the battery voltage is V...
Homework Statement
The figure opposite shows a free oscillator composed of an LC circuit. Derive an expression for the resonance frequency. Show all of your working.
Homework Equations
d2x/dt2 + ω2x = 0
The Attempt at a Solution
First I tried using Kirchoffs Voltage Law to set...
Hey guys,
So I'm working on this project, and I'm trying to make two coils of different diameters to be tuned to the same resonance frequency. I got the equation ω=1/(LC)^0.5 for the frequency. My thinking was that the frequency of the wall power shouldn't matter because the resonance...
Homework Statement
I have a series LC circuit that consists of a 1V DC voltage supply, an inductor and a capacitor. The inductance of the inductor is 2mH and the capacitance of the capacitor is 1μF. I performed a transient analysis using a simulation software and I observed the trace of the...
Hello all,
I am trying to make an FM transmitter that operates at only 1 frequency. I need the frequency tolerance to be very high, so I'd like to choose a crystal instead of an LC circuit.
This is the circuit I'm building: http://cappels.org/dproj/FMdist/fmdis.htm
If I were to replace...
So I was learning about the LC circuit and I know that an inductor would oppose the change in current through it, so if I connect a charged capacitor with an inductor, the charges on the capacitor would want to flow to the other side and neutralize the two plates like it does when the two plates...
Homework Statement
. In the following transient circuit, assume at t<0, the circuit is at steady state.
Find v0(t) for t>0
http://sphotos-b.xx.fbcdn.net/hphotos-ash3/c0.0.354.354/p403x403/546839_509413575744829_42997155_n.jpg
Homework Equations
The Attempt at a Solution
The...
1. Homework Statement
Calculate capacitance of LC Circuit where:
Inductor - 30H
Capacitance voltage fully charged goes to zero in 20 seconds
2. Homework Equations
Main Eq: V=V. *cost(ωt) where V is final Voltage, V. = Voltage initial, ω = resonant angular frequency
ω = 1/√(LC)...
Homework Statement
Calculate capacitance of LC Circuit where:
Inductor - 30H
Capacitance voltage fully charged goes to zero in 20 seconds
Homework Equations
Main Eq: V=V. *cost(ωt) where V is final Voltage, V. = Voltage initial, ω = resonant angular frequency
ω = 1/√(LC) = 2∏f
f. =...
I'm reading University Physics 13e by Young and Freedman and we're given this equation:
-L(di/dt)-q/C=0
So we know that i, current, is, i=dq/dt. So the first equation can be read, after some simplification, as
q''+(1/LC)q=0
where q prime means the derivative of q (charge) with...
Homework Statement
An oscillating LC circuit is designed to operate with a maximum current of 31 mA. The inductance is fixed at 42 mH, and the frequency is changed by means of a variable capacitor C. (a) If the highest voltage that the capacitor can handle is 50 V, can the circuit be operated...
I'm trying to make a wireless energy experiment by using LC circuits as resonators. But within this circuit you can either make the inductor and capacitor in series or in parallel. What do the different combinations do to the circuit? Is there one that is ideal for some circumstances?
Hello guys
This is my first post and i am glad to be a member of this forum. There is something bugging me for a lot of time. I have a problem understanding why the current of an LC oscilator circuit is maximized when the capacitor is fully discharged. Of course when it is explained from the...
Alright, I have an LC circuit.
Using conservation of energy, I get \frac{dI}{dt}= \frac{-q}{CL} which gives \frac{d^2q}{dt^2}= \frac{-q}{CL}, therefore, q=q_o sin(\omega t +\phi), where \omega= \frac{1}{\sqrt {LC}}, giving q=q_o cos(\omega t) which implies I= -q_o \omega sin(\omega t).
Now...
Homework Statement
A constant voltage at a frequency of 1MHz is maintained across a circuit consisting of an inductor in series with a variable capacitor. When the capacitor is reduced from 300pF to 284pF, the current is 0.707 of its maximum value. Find
(i) the inductance and the resistance...
I recently read that a 1/4 wave resonator is equivalent to a series lc circuit but with a much higher q.
In a typical resonant LC series circuit voltage magnifications exists, does the same thing occur in a 1/4 resonator since it is equivalent to a series LC circuit?
Thanks in advance!
LC circut: Charge on a capacitor at a given time
Homework Statement
I don’t have a pic but a simple loop circuit is constructes with 2 capacitors c1 and c2 in series, after the capacitors in an inductor also in series, and the wire continues back into c1. The values for the capacitors...
In an oscillating LC circuit, L=25 mH and C=7.8 x10^-6 F. At time t=0 the current is 9.2 mA, the charge on the capacitor is 3.8 x 10^-6 C, and the capacitor is charging. What is the total energy in the circuit?
I know I just need to do Ub+Ue=U, but here is my question. Are L and C constant...
Homework Statement
An LC circuit is shown in the figure below. the 33 pF capacitor is initially charged by the 6V battery when S is at position a. Then S is thrown to position b so that the capacitor is shorted across the 15 mH Inductor.
Homework Equations
w= 1/sqrt(LC)
XL = wL...
A series LC circuit at resonance has a higher total voltage than the applied voltage due to voltage magnification.
If a diode were inserted between L and C it would prevent the back and forth oscillation of energy, But would it prevent voltage magnification if the circuit were driven at...
I am trying to figure out what the voltage across each component will be. In the cirucit above resonance occurs between inductor L1 (5 Henries) and Capacitor C1 (10nF) The other inductor (L2) is 10 Henries and the circuit's resistance is 1,000 Ohms.
Here's my attempt at figuring the voltage...
Homework Statement
An LC circuit constructed of a 1 microF capacitor and a 1 microH inductor
is set in oscillation so that the charge on the capacitor is 1.0 microC at t = 0
and 2.0 microC at t = 1.57 x 10^-6 s. What is the charge on the capacitor at
t = 1.0 s?
Homework Equations
Q(t) =...
Homework Statement
There's an LC circuit that's made of an 31 mH inductor and a planar capacitator. The surface of the plate is 20cm^2 and the distance between the plates is 1 cm. What is the electrical permittivity of the insulator between the plates , if the peak current is 0,2mA and the...
Homework Statement
Since I don't have a pic.. I will explain my problem. I have a circuit with 3 terminals x , y and z.
Between x - z I have a resistance , say R,
Between z - y I have an inductor L and then a capacitor C in series.
I apply a square wave input between x and y. Homework...
I wonder if LC curcit radiates energy? Probalby not because according
to equations energy is not lost during its vibration. But I heard it was used
in very simpe radio receivers. Is it true.
I have been thinking about a scenario in which I might have a series LC circuit, but where one plate on the parallel-plate capacitor is attached to a spring. How would I model such a scenario, and how would I determine the ideal resonant frequency of the entire system?
I have attempted two...
Homework Statement
An LC circuit with an inductor of 4 microH is used as tuner for an FM radio. The capacitance required to tune into a radio stations of 100 MHz is most nearly what?
Homework Equations
w= 2pif = 1/sqrt LC
The Attempt at a Solution
I plugged in 4 microH into...
Homework Statement
In an oscillating LC circuit, L = 2.93 mH and C = 3.21 μF. At t = 0 the charge on the capacitor is zero and the current is 2.14 A. What is the maximum charge (in C) that will appear on the capacitor?
Homework Equations
I know that for an LC Circuit, the charge q at...
A circuit has a battery(V), Capacitor(C) and Inductor(L) connected in series. At t < 0, the switch is open and the capacitor has an initial charge of -800uC and Io = 0.0Amps.. When the switch is closed at t = 0, I want to know what happens here. I only understand an LC circuit where there is...
Homework Statement
A circuit consists of a capacitor and an inductor. The resistance in the circuit is small and can be neglected. Initially, at t = 0 s, the voltage across the capacitor is at its maximum of VC = 10 V, the charge stored in the capacitor is 1 mC. It is observed that the...
"At resonance frequency, the circuit impedance is maximum. It is resistive and its value is given L/Cr..."
The book doesn't explain how impedance equals L/Cr, so I'm confused here. How is it derived?
"At resonance frequency, the circuit impedance is maximum. It is resistive and its value is given L/Cr..."
The book doesn't explain how impedance equals L/Cr, so I'm confused here. How is it derived? (Can you please show all the steps?)
Thanking in advance...
Homework Statement
The 300 μF capacitor is initially charged to 100 V, the 1200 μF capacitor is uncharged, and the switches are both open. So the picture is two capapcitor in either side of the circuit. There is a inductor 5.3 H in the middle wire that divide the switches in eaither side of...
What size capacitor would you install in a series-tuned LC circuit with a resonant frequency of 2 KHz the circuit will include a 2 mH inductor?
This is my question and here is what I got. Just want to know if it is right.
2.52 i do not know how to put the formula in here.
can anyone show me...
I thought these were weird similarities between macroscopic electronic circuits and (Bohr) hydrogen model. What do you guys think?
.
hydrogen self-capacitance (energy level "capacitance")
C = 4*pi*eo*br = 5.88798e-21 Farads
eo = vacuum permitivity
br = Bohr Radius
m = electron mass
e =...
At t = 0, Q0 = 18 C and I = 0 in an LC circuit.
(a) At the first moment when the energy is shared equally by the inductor and the capacitor, what is the charge on the capacitor?
Homework Statement
A radio receiver contains an LC circuit whose natural frequency of oscillation can be adjusted, or tuned, to match the frequency of the incoming radio waves. The adjustment is made by means of a variable capacitor. Suppose that the inductance of the circuit is 11.00 μH. What...
I understand how an LC circuit oscillates and radio waves are a result. I also understand that any light from the electromagnetic spectrum has an electrical and magnetic component. Where does the magnetic component come into play in an LC circuit. Thanks.
A series LC circuit contains a 100 mH inductor, a 36.0 mF capacitor and a 12 V battery. The period of the electromagnetic oscillations in the circuit is
1. 0.0227 s.
2. 1750 s.
3. 105 s.
4. 2.26 s.
5. 0.376 s.
f= 1/ 2*π *√L *C
L =100mH
C= 36uF
so,,f = 2.65...
[SOLVED] Finding current in LC circuit
Homework Statement
A 18.0 \mu {\rm F} capacitor is placed across a 22.5 {\rm V} battery for a few seconds and is then connected across a 12.0 \rm mH inductor that has no appreciable resistance.
After connecting the capacitor and inductor together, find...
Homework Statement
An LC circuit starts at t=0 with its 2000 microF capacitor at its peak voltage of
14V. At t=35 ms the voltage has dropped to 8.5 V.
a) What will be the peak current?
b) At what time will the peak current occur?
c) What must be the value of the inductor in the circuit?The...
Hello guys. I have a simple question regarding an LC circuit.
Imagine a voltage source V_0, a capacitor C and an inductor L, all hooked up in series. I know that the equation governing the behvior of the system is
V_0=\frac{1}{C}q(t)+L\ddot{q}(t),
and hence
q(t)=A\cos \omega t +...
Homework Statement
I need to design a series-tuned LC circuit with a resonant frequency of 2 kHz and and a 2 mH inductor. I need to know what size capacitor I would need?
Homework Equations
2 kHz * 1000 = 2000 Hertz
2 mH / 1000 = 0.002 Henry
The Attempt at a Solution
Homework Statement
An AC source is connected to an LRC circuit (Inductor is connected to Capacitor in series, and then it is connected to register in series). Energy is stored in the capacitor and inductor and is dissipated in the resistor. At what time is the energy dissipated at the maximum...
Hi,
I was just wondering if someone could point in the right direction to find formulas to calculate the natural resonant frequency of an LC oscillator circuit that uses and air core coil rather than a metal one.
Thanks :-)
A fixed inductance 0.66 \mu H is used in series with a variable capacitor in the tuning section of a radio. What capacitance tunes the circuit into the signal from a station broadcasting at 8.11 MHz? Answer in units of pF.
I used the equation \omega = 1/ \sqrt LC
Solving for C gave me...