NAME: ___________________________

PAGE 3AC-Bank-master

QUIZ - Alternating Current

Level - I 1. The capacitor reactance of a capacitor in d.c. circuit in ohms is

(A)

(B) (C(C) zero(D) (

2. The reactance of a inductor at 50 Hz is 10 (. What will be its reactance at 200 Hz ?

(A) 10 ((B) 40 ( (C) 2.5 ((D) 20 (3. In a series R-L-C circuit, R = 100 (, XL = 300 ( and Xc = 200 (. The phase angle ( of the circuit is

(A) 00(B) 900 (C) 450(D) 450

4. In a series LRC circuit, resonance occurs when

(A) R = XL ~ XC (B) XL = XC (C) XL = 10 XC more (D) XL XC > R

5. An inductive circuit contains a resistance of 10 ( and inductance of 2H. If an a.c. voltage of 120 V and frequency 60 Hz is applied to this circuit, the current in circuit would be nearly

(A) 0.32 A(B) 0.16 A(C) 0.48 A(D) 0.80 A

6. What is the average value of a.c. over a half cycle

(A) zero (B)

(C)

(D) none of these

7. In an AC circuit having R and L in serries

(A) voltage leads current

(B) current leads voltage

(C) voltage and current are increase

(D) voltage and current are in opposite phase

8. Average power in a pure inductive circuit is

(A) irms ( vrms(B) 2 irms ( vrms(C) 1(D) zero

9. The root mean square value of voltage (V) in an AC circuit is

(A) 0.637Vmax(B) 0.707 Vmax (C) 2Vmax(D) Vmax

10. The power factor in AC circuit is equal to

(A) Z/R(B) R/Z(C) RZ(D) none of the above

11 A series AC circuit has a resistance of 12 ( and reactance 5 (. The impedance of circuit is

(A) 5 ((B) 12 ((C) 13 ((D) 17 (12 In an AC series circuit, instantaneous voltage is maximum while instantaneous current is zero. The source is connected to

(A) pure inductor only

(B) pure resistance only

(C) pure capacitor only

(D) (A) or (C) 13 In the circuit shown, the voltage in C & L are

(A) out of phase by ((B) out of phase by (/2

(C) out of phase by (/4(D) in phase

14. If the mean value of an alternating voltage is volt, its rms value is

(A) 28 volt(B) 14 volt(C) 14 volt(D)zero

15. When an alternating voltage source is connected to a pure inductor, the difference between phase of instantaneous current through the inductor and the phase of instantaneous potential difference across the inductor at t = T/4 sec. is

(A) zero(B) (/2 rad.(C) -(/2 rad.(D) (/4 rad.

Level - II1. In an a.c. circuit voltage v and current i are given by v = 100 sin 100 t volts,i = 100 sin {100 t + (/3} mA. The power dissipated in the circuit is

(A) 104 W(B) 10 W (C) 2.5 W(D) 5 W

2. In the a.c. circuit shown in the following figure, the resultant potential difference is

(A) 110 V(B) 10 v

(C) 50 V(D) 70 V

3. An alternating voltage E = E0 sin (t, is applied across a coil of inductor L. The current flowing through the circuit at any instant t is

(A) E0 / (L sin ((t + (/2) (B) E0 / (L sin ((t - (/2)

(C) E0 (L sin ((t - (/2) (D) E0 (L sin ((t + (/2)

4. In an R-L-C circuit v = 20 sin (314 t + 5(/6) and i = 10 sin (314 t + 2(/3)

The power factor of the circuit is

(A) 0.5 (B) 0.966 (C) 0.866(D) 1

5. An alternating current is given by i = i1 cos (t + i2 sin (t. The rms current is given by

(A) i1 + i2

(B) ()2 (C)

(D) none of the above

6. The impedance of the circuit is

(A)

(B)

(C)

(D) none of the above

7. In the figure shown the steady state current through the inductor will be

(A) zero

(B) 1A

(C) 1.25 A

(D) can not be determined

ANSWERS Level - I

1.A2.B3.C4.B5.B

6.C7.A8.D9.B10.B

11.C12.D13.A14.B15.C

LEVEL II

1.D2.C3.B4.C5.D

6.A7.C

_1150277744.unknown

_1176125696.unknown

_1176125698.unknown

_1306752470.doc

~

R

L

C

30V

60V

20V

_1176125699.doc

~

C

L

R

_1176125697.unknown

_1176125694.unknown

_1176125695.unknown

_1150277745.unknown

_1117101846.doc

~

C

L

_1117379393.unknown

_1150276168.unknown

_1117380771.doc

3mH

4F

1

4

5 V

_1117379355.unknown

_1117017250.unknown