The impedance of a series L-C-R circuit at resonance is: 

Concept:

• Resonance: It is a phenomenon in which a vibrating system or external force drives another system to oscillate with greater amplitude at specific frequencies.
  • Example: Playground swing, which acts as a pendulum.
• Average power: It is the average amount of work done or energy converted per unit of time.
• SI unit: watt (W)
• Impedance: It is the measure of the total opposition provided by the circuit or a part of a circuit presents to electric current.
  • Impedance includes both resistance and reactance

The impedance of the series RLC circuit is given by,

Where XC = Capacitive reactance, XL = Inductive reactance, Z = Total circuit impedance

At Resonance XC = XL

Z = R