Basic AC Reactive Components RESONANCERESONANCEIn the chapters on inductance and capacitance we have learned thatboth conditions are reactive and can provide opposition to current flow,but for opposite reasons. Therefore, it is important to find the pointwhere inductance and capacitance cancel one another to achieveefficient operation of AC circuits.EO 1.15 DEFINE resonance.EO 1.16 Given the values of capacitance (C) and inductance (L),CALCULATE the resonant frequency.EO 1.17 Given a series R-C-L circuit at resonance, DESCRIBEthe net reactance of the circuit.EO 1.18 Given a parallel R-C-L circuit at resonance, DESCRIBEthe circuit output relative to current (I).ResonantFrequencyResonanceoccurs in an AC circuit when inductive reactance and capacitive reactance are equalto one another: X_{L} = X_{C.} When this occurs, the total reactance, X = X_{L} - X_{C} becomes zero andthe impendence is totally resistive. Because inductive reactance and capacitive reactance are bothdependent on frequency, it is possible to bring a circuit to resonance by adjusting the frequencyof the applied voltage. Resonant frequency (f_{Res}) is the frequency at which resonance occurs, orwhere X_{L} = X_{C}. Equation (8-14) is the mathematical representation for resonant frequency.(8-14)f_{Res}12p LCwheref_{Res}= resonant frequency (Hz)L = inductance (H)C = capacitance (f)SeriesResonanceIn a series R-C-L circuit, as in Figure 9, at resonance the net reactance of the circuit is zero, andthe impedance is equal to the circuit resistance; therefore, the current output of a series resonantcircuit is at a maximum value for that circuit and is determined by the value of the resistance.(Z=R)IV_{T}Z_{T}V_{T}RRev. 0 Page 19 ES-08

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