M.C.Q : Alternating Current ( 11 to 20)

11. In the given figure, which voltmeter will read zero voltage at resonant frequency ω rad/sec ?

(A) V1

(B) V2

(C) V3

(D) V4

12. A resistance R Ω is connected in series with capacitance C Farad value of impedance of the circuit is 10 Ω and R = 6Ω so, find the power factor of circuit.

(A) 0.4

(B) 0.6

(C) 0.67

(D) 0.9

13. In a R, L, C circuit, three elements is connected in series by an a.c. source. If frequency is less than resonating frequency then net impedance of the circuit will be

(A) capacitive

(B) inductive

(C) capacitive or inductive.

(D) pure resistive.

14. Using an A.C. voltmeter, the potential difference in the electrical line in a house is read to be 234 volts. If the line frequency is known to be 50 cycles per second, the equation for the line voltage is

(A) V = 165 sin(100πt)

(B) V = 331 sin(100πt)

(C) V = 234 sin(100πt)

(D) V = 440 sin(100πt)

15. In an a.c. circuit, containing an inductance and a capacitor in series, the current is found to be maximum when the value of inductance is 0.5henry and of capacitance is 8μF. The angular frequency of the input A.C. Voltage must be equal to

(A) 500

(B) 5×104

(C) 4000

(D) 5000

16. An alternating voltage E (in volts) = 200√2 sin (100t) is connected to a 1 μF capacitor through an a.c. ammeter. The reading of the ammeter shall be

(A) 10mA

(B) 20mA

(C) 40mA

(D) 80mA

17. In a series R, L, C circuit XL = 10Ω , XC = 4Ω and R = 6Ω. Find the power factor of the circuit.

(A) 1/√2

(B) √3/2

(C) 1/2

(D) none of the these.

18. In LCR circuit the capacitance is changed from C to 4C. For the same resonant frequency, the inductance should be changed from L to

(A) 2L

(B) L/2

(C) L/4

(D) 4L

19. A resistance (R) = 12Ω; inductance (L) = 2 henry and capacitive reactance C = 5 mF are connected in series to an ac generator

(A) at resonance, the circuit impedance is zero.

(B) at resonance, the circuit impedance is 12Ω.

(C) the resonance frequency of the circuit is 1/2π.

(D) at resonance, the inductive reactance is less than the capacitive reactance.

20. In an A.C. circuit, the current is I = 5 sin(100 – π/2) amp and the A.C. potential is V = 200 sin(100t) volt. Then the power consumption is

(A) 20 watts

(B) 40 watts

(C) 1000Watts

(D) 0 watts

ANSWER:

11. (D)    12. (B)   13. (A)    14. (B)    15. (A)    16. (B)    17. (A)    18. (C)    19. (B)    20. (D)   

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