AC2 Fundamentals Unit 2 – Series Resonance
At resonance, the reactances are equal, so they cancel one another (XL - XC). The total circuit
impedance of a series RLC circuit at resonance is simply the circuit resistance (R1).
This response curve shows that as frequency increases, the circuit impedance (Z) decreases until
it reaches a minimum point (R), then it increases again.
This response curve shows that as frequency increases, the circuit current (IT) increases until it
reaches a maximum point (IRESON), then it decreases again.
RLC series circuits are widely used in radio, TV, and communications equipment for tuning and
filtering because they allow a large peak current at the resonant frequency and provide a high
opposition to current flow at all other frequencies. This ability to select a desired frequency while
rejecting other frequencies is known as selectivity.