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In a parallel resonant circuit, the input impedance of the circuit is ________.
maximum
zero
infinite
minimum
maximum
In a parallel resonant circuit (tank circuit), the circuit reaches resonance when the inductive reactance equals the capacitive reactance. At this frequency, the circuit exhibits maximum impedance, resulting in minimum line current for a given supply voltage.
In a parallel resonant circuit (tank circuit), the circuit reaches resonance when the inductive reactance equals the capacitive reactance. At this frequency, the circuit exhibits maximum impedance, resulting in minimum line current for a given supply voltage.
frтАЛ=2╧АLCтАЛ1тАЛ тАФ Resonant frequency formula
ZmaxтАЛ=CRLтАЛ тАФ Dynamic impedance at resonance
Y=G2+(╧ЙCтИТ╧ЙL1тАЛ)2тАЛ тАФ Admittance of parallel RLC circuit
At resonance, the reactive components XLтАЛ and XCтАЛ cancel each other out. Since the current through the inductor ILтАЛ and the current through the capacitor ICтАЛ are equal in magnitude but 180┬░ out of phase, they neutralize, leaving only the resistive component. Because the admittance Y=G2+(BCтАЛтИТBLтАЛ)2тАЛ is minimized at resonance (BCтАЛ=BLтАЛ), the impedance Z=Y1тАЛ reaches its theoretical maximum.
At parallel resonance, the power factor of the circuit is unity.
The line current is in phase with the applied voltage.
The circuit acts as a pure resistor at resonant frequency.
The magnitude of current flowing through the individual L and C branches can be much higher than the supply current.
Used in radio frequency tuning circuits
Effective at selecting specific frequencies while rejecting others
Sensitive to component tolerances
Requires high-quality inductors to achieve sharp resonance
Band-pass filters
Oscillator circuits
Radio frequency (RF) amplifiers
| Feature | Parallel Circuit | Series Circuit |
|---|---|---|
Impedance at Resonance | Maximum | Minimum |
In a series resonant circuit, impedance is minimum (equal to R).
Option B (zero) is impossible for a practical resonant circuit as it would imply a short circuit.
Option C (infinite) is only true for an ideal parallel circuit with zero resistance (R=0).
A is correct тАФ In a parallel resonant circuit, the impedance reaches its maximum value at the resonant frequency.
Remember the mnemonic: 'Parallel is Maximum Z, Series is Minimum Z' to avoid confusion during rapid-fire MCQ exams.
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