Contents
What happens in a LC circuit?
An LC circuit, oscillating at its natural resonant frequency, can store electrical energy. A capacitor stores energy in the electric field (E) between its plates, depending on the voltage across it, and an inductor stores energy in its magnetic field (B), depending on the current through it.
What is the maximum current in LC circuit?
The current is a maximum when the charge on the capacitor is zero. Current and charge are exactly 90 degrees out of phase in an ideal LC circuit (no resistance), so when the current is maximum the charge must be identically zero.
Why is the Q factor low in a resonant circuit?
Voltage is at a peak at resonance since voltage is proportional to impedance (E=IZ). Parallel resonant circuit: Impedance peaks at resonance. A low Q due to a high resistance in series with the inductor produces a low peak on a broad response curve for a parallel resonant circuit.
How to make quality factor ( Q ) measurements on L-C circuits?
Transmission methods are traditionally used for making quality factor (Q) mea- surements on L-C circuits. This implies that a signal source and an RF voltmeter or spectrum analyzer must be available for such measurements. These are not always available however.
How is the bandwidth of a low resistance circuit measured?
A low resistance, high Q circuit has a narrow bandwidth, as compared to a high resistance, low Q circuit. Bandwidth in terms of Q and resonant frequency: Bandwidth is measured between the 0.707 current amplitude points. The 0.707 current points correspond to the half power points since P = I 2R, (0.707) 2 = (0.5).
What is the formula for Q stored / dissipated?
Q = P stored/P dissipated = I 2X/I 2R Q = X/R where: X = Capacitive or Inductive reactance at resonance R = Series resistance. This formula is applicable to series resonant circuits, and also parallel resonant circuits if the resistance is in series with the inductor.