1. For a series or parallel LC circuit, resonance occurs when _______.
(A) XL = 10XC
(B) XL = XC
(C) XC = 10XL
(D) The phase angle of circuit is 90°
2. When either L or C is increased, the resonant frequency of the LC circuit _______.
(A) Increases
(B) Is determined by shunt R
(C) Remains the same
(D) Decreases
3. The resonant frequency of an LC circuit is 1000 KHz. If L is doubled and C is reduced to 1/8th, the resonant frequency is _______.
(A) 250 KHz
(B) 500 KHz
(C) 2000 KHz
(D) 1000 KHz
4. A coil has a 1000 Ω XL & 5 Ω Ri. Its Q equals _______.
(A) 1000
(B) 5
(C) 500
(D) 200
5. In a parallel LC circuit, at the resonant frequency, the _______.
(A) Line current is maximum
(B) Total impedance is maximum
(C) Total impedance is minimum
(D) Inductive branch current is minimum
6. At resonance, the phase angle equals _______.
(A) 270°
(B) 90°
(C) 180°
(D) 0°
7. In a series LC circuit, at resonant frequency, the _______.
(A) Current is minimum
(B) Voltage across C is minimum
(C) Impedance is maximum
(D) Current is maximum
8. A series LC circuit has a Q of 100 at resonance. When 5 mV is applied at resonant frequency, the voltage across C equals:
(A) 5 mV
(B) 500 mV
(C) 100 mV
(D) 20 mV
9. An LC circuit is resonant at 1000 KHz & has a Q of 100. The bandwidth between half power points is _______.
(A) 10 KHz b/w 995 and 1005 KHz
(B) 10 KHz b/w 1000 and 1010 KHz
(C) 5 KHz b/w 995 and 1000 KHz
(D) 200 KHz b/w 900 and 1100 KHz
10. In a low Q parallel resonant circuit, when XL = XC _______
IC')"> (A) IL = IC
IC')"> (B) IL < IC
IC')"> (C) The phase angle is 0°
IC')"> (D) IL > IC
11. Resonance curve shows variation of circuit current with _______.
(A) Voltage
(B) Frequency
(C) Band width
(D) All of these
12. Higher the Q-factor of a circuit _______ its bandwidth.
(A) Expansion
(B) Narrower
(C) Increase
(D) Widen
13. Lower the resistance of a resonant circuit, _______ its selectivity.
(A) Better
(B) Narrower
(C) Decrease
(D) Bad
14. Sharpness of tuning depends _______ on the Q of a coil.
(A) Minimum
(B) Complete
(C) Maximum
(D) Inversely
15. In parallel resonance, the line current is __ at the resonant frequency.
(A) Maximum
(B) Often
(C) Complete
(D) Minimum
16. Band width of a series resonant circuit depends on --
(A) R
(B) L
(C) C
(D) All of the above
17. The power factor of a resonant series circuit is ___
(A) 1
(B) 6
(C) 1
(D) 0.5
18. Higher the Q factor of a series circuit _______.
(A) Greater its bandwidth
(B) Broader its resonance curve
(C) Sharper its resonance curve
(D) Narrower its pass band
19. As the Q factor of a circuit _______ its selectivity becomes _______.
(A) Decrease, better
(B) Increase, worse
(C) Increase, better
(D) None of these