Question

Under what conditions is the impedance in an LRCcircuit a minimum?

Answer 1

Under what condition is the impedance in an LRC circuit is minimum

Answer: - Impedance of an LRC circuit is given by,

Z = √R² + (XL – XC) 2

Where,

R – Resistance

XL – Inductive reactance = ωl = (L – inductance, ω – angular frequency)

XC – Capacitive reactance = 1/ωc = (capacitance)

The values of XL and XC vary with the frequency. And at resonance both are equal. Thus at resonance XL = XC and the impedance has minimum.

At resonance in series LRC circuit two reactance becomes equal and cancel each other so in resonant series LRC circuit, the opposition to the flow of current is due to only resistance, At resonance the total impedance of series circuit is equal to resistance Z = R impedance has only real part but no imaginary part and this impedance at resonant frequency is called dynamic impedance. And this dynamic impedance is always less than in series LRC circuit.

In LRC circuit current I = V/Z but at resonant current, I = V/R, therefore the current at resonant frequency is maximum as resonance in impedance of circuit is resistance only and is minimum.