How does series resonant circuit work?

[mujee]

hi guys
i am a basic level student of electronics. currently we are studying electric circuits.
yesterday we were taught series resonant circuit in which an ac voltage source, a capacitor and an inductor are connected in series. we were told when the capacitive and inductive reactances become equal , the circuit comes into resonance state

i want to know how does this circuit actually work. my point is when ac voltage source is actuated, the capacitor will start charging but inductor will resist it, so how come current gonna move through this series circuit

please answer in detail as it takes me time to grasp the concept if things are said concisely

 

[kevpat]

Re: resonant circuit

Simple answer is that the AC impedances of the two elements cancel each other out at a specific frequency so a large current will flow at that frequency. Instead of going into a detailed analysis here I have added a couple of links one has a nice little flash application where you can play about with circuit values of the L and C elements and see how it effects the resonance frequency.


h**p://hyperphysics.phy-astr.gsu.edu/hbase/electric/serres.html#c2

h**p://www.allaboutcircuits.com/vol_2/chpt_6/index.html

 

[Sal]

resonant circuit

Hi

It seems alternating current is driving you crazy. You may need a lot of reading. I found this great tutorial which can be used as an start point, **broken link removed**

you may find many other in the web

Sal

 

[mujee]

Re: resonant circuit

no its not ac thats driving me nuts
actually i dont need mathematical explanation of this circuit i.e when impedences become equal they cancel each other out as they are in opposing direction

what i want to know is the actual working of this circuit...i want to know what happens during the positive cycle of sinusoid and what happens during the negative cycle. its very intriguing as both are connected in series...if one is able is conduct at a point the other is more bent on blocking it at that instant

i have searched alot on internet for this, but everywhere it has that same phasor explanation...

is there anyone who could help

 

[IBO]

Re: resonant circuit

resonance occurs due to simultaneous exchange of electric and magnetic field,
between L and C.

Are u looking for a physical approach

 

[mujee]

Re: resonant circuit

yeah IBO
it would be great if u could help me with that

u know its been more than a week that i am stuck with it...couldnt read further
i cant just memorize things. unless i get the whole picture , i cant move further

your help would be greatly appreciated

 

[mujee]

Re: resonant circuit

no reply

i thought IBO would come with an answer that would solve my problem

 

[Kral]

Re: resonant circuit

mujee,
In a series circuit, the currents in all elements are equal (forgive me for stating the obvious). The fundamental relationship among voltage, inductance and time is: V(L) = Ldi/dt. This means that the voltage across the inductor leads the current by 90deg. (The derivative of the sin is the cosine). The fundamental relationship among voltage, capacitance and time is: I = C dv/dt. Solving for V, and ignoring the constant of integration, v=(1/C)∫Idt. This means that the voltage lags the current by 90deg. (The integral of the sine is the negative of the cosine).
.
We now have two voltages that are exactly out of phase with each other. At some frequency (f), the inductive reactance Xl= 2pif will exactly equal the capacitive reactance Xc=1/(2piC). At this frequency, not only will the two voltages be exactly out of phase (This is true at all frequencies), but they will be equal in magnitude (The reactance are equal, and the currents are equal), so the current goes to infinity, the individual voltage magntudes go to infinity, and the net impedance across the capacitor-inductor combination is zero. This, of course is an impossible situation in the real world, However, if we insert a resistance into the series circuit, the the net impedance will simply be the resistance of the resistor, but the circuit will still be in resonance. The current will equal the applied voltage divided by the resistance of the resistor.
Regards,
Kral

 

[Electronica]

resonant circuit

resonance because of electric and magnetic field, of
L and C.

Added after 7 seconds:

resonance because of electric and magnetic field, of
L and C.