Question

Which of the following statements is incorrect?

1.  During parallel resonance impedance at resonance is minimum
2.  During parallel resonance current is magnified
3. During series resonance current at resonance is maximum
4. During series as well as parallel resonance, the power factor is unity

Answer 1

Correct Answer - Option 1 :  During parallel resonance impedance at resonance is minimum

Concept:

• In a series RLC circuit, at resonance condition impedance is purely resistive and it is equal to R. It is the minimum impedance condition. Hence the current at this condition is maximum.
• In parallel RLC circuit, at resonance condition impedance is purely resistive and it is equal to R. It is the maximum impedance condition. Hence the current at this condition is minimum.

• In parallel RLC circuit current through the inductor and current through the capacitor is greater than the source current, this phenomenon is called current magnification. 
• The magnitude of current flowing through the inductor and capacitor is equal to Q times the input sinusoidal current.

 

Specifications	Series resonance circuit	Parallel resonance circuit
Impedance at resonance	Minimum	Maximum
Current at resonance	Maximum	Minimum
Effective impedance	R	L/CR
It magnifies	Voltage	Current
It is known as	Acceptor circuit	Rejector circuit
Power factor	Unity	Unity