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Series LC and Parallel LC circuits

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Dan Yoder

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Hi All,
I am new here and would like to have someone explain to me why the resonant series LC circuit has a current increase and the resonant parallel LC circuit has a decrease or dip. I think I understand that the parallel circuit has no or very little resistance and the series has the Xc and Xl subtracted from each other. In a parallel resonant tank circuit the resonant freq goes to the diode and all the rest go to ground.
Thanks Dan
 
Dan Yoder,
In a series resonant circuit, the L is accepting energy while the C is dispensing the same amount of energy. Then the L and C reverse roles. This allows the back voltage of the capacitor to stay low and the current of the inductor to stay high at the same time. Thus it is equivalent to no total circuit reactance, and the current is limited only by the resistance in the circuit. A series resonant has only one resonant frequency.

In the parallel resonant circuit, the L and C swap equal energy at with each other, and do not let any current to exist outside the LC loop. A parallel resonant circuit has three defined frequencies. They are equal reactance, zero phase between the voltage and current, and max impedance. I believe the equal reactance of L and C is the only correct definition. If the Q of the circuit is not low, the three frequencies are close together. It is also possible to make a parallel circuit resonant at all frequencies.

See the following for more info. https://www.electro-tech-online.com/threads/rlc-parallel-resonance-circuit.114932/page-2#post-942573

Ratch
 
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