NETWORK ANALYSIS

N.1) In an RC series circuit R = 100 Ω and $X_C$ = 10 Ω. In this circuit
(a) the current and voltage are in phase
(b) the current leads the voltage by about 6°
(c) the current leads the voltage by about 84°
(d) the current lags the voltage by about 6°
Answer is (b)

N.2)Given two coupled inductors L1 & L2 their Mutual inductance M, satisfies
(a) $M = \sqrt{L_1^{2}+L_2^{2}}$
(b) $M >\frac{L_1+L_2}{2}$
(c) $M >\sqrt{L_1L_2}$
(d) $M \leq \sqrt{L_1L_2}$
Answer is (d)

N.3) In an ac circuit, the maximum and minimum values of power factor can be
(a) 2 and 0
(b) 1 and 0
(c) 0 and -1
(d) 1 and -1
Answer is (b)

N.4)An AC Source of 200V rms supplies an active power of 600W and reactive power of 800VAR. The rms current drawn from the source is
(a) 10A
(b) 5A
(c) 3.75A
(d) 2.5A
Answer is (b)
Explanation: $V_{s} = 200V (rms)$
$P = 600W , Q = 800VAR$
$P = V_{s}I_{s}cos\phi = 600$
$\therefore I_{s}cos\phi = 600/200 = 3 $...Eqn(1)
$Q = V_{s}I_{s}sin\phi = 800$
$\therefore I_{s}sin\phi = 800/200 = 4 $...Eqn(2)
$\therefore$ From Eqn(1) and (2) $I_{s}^{2}(sin^{2}\phi + cos^{2}\phi)$ = 9 +16 = 25


N.5)A 10mH inductor carries a sinusoidal current of 1A rms at a frequency of 50Hz.The average power dissipated by the inductor is
(a) 0 W
(b) 0.25 W
(c) 0.5 W
(d) 1 W
Answer is (a)
Explanation:The average power dissipated by a circuit which has only reactive element(purely capacitive or purely inductive) is 0.

N.6)In the circuit shown , the current I supplied by sinusoidal current source is
(a) 28 A
(b) 4 A
(c) 20 A
(d)insufficient data
Answer is (c)
Explanation:

$\overrightarrow I = \overrightarrow I_{R} + \overrightarrow I_{L}$
$\lvert I \rvert = \sqrt{ 144 + 256}$ = 20 A

N.7)In series RLC circuit
(a) Current lags $V_{L}$ by 90°
(b) Current leads $V_{L}$ by 90°
(c) $X_{L}$ leads $X_{C}$ by 90°
(d) $Z = j*X_{L}$ at resonance
Answer is (a)

N.8)Property of an electric circuit that dissipates electric energy is
(a) Reactance
(b) Impedance
(c) Resistance
(d) Conductance
Answer is (c)

N.9)In the circuit shown in figure,current in 2Ω resistor is
(a) zero
(b) -2A
(c) 2A
(d) 1A
Answer is (c)
Explanation:
N.10) Current is __ times the maximum current at half power points of resonance
(a) 0.707
(b) 1.414
(c) 0.5
(d) 0.632
Answer is (a)

N.11) If three 9mH inductors are connected in parallel without mutual inductance then the total inductance will be
(a) 3 mH
(b) 9 mH
(c) 27 mH
(d) 18 mH
Answer is (a)

N.12) A network contains only independent current sources and resistors. If the values of all resistors are doubled,the values of the node voltages
(a) will become half
(b) will remain unchanged
(c) will become double
(d) cannot be determined
Answer is (c)

N.13)A 3-phase star connected symmetrical load consumes P watts of power from a balanced supply. If the same load is connected in delta to the same supply,the power consumption will be
(a) P
(b) $\sqrt{3P}$
(c) 3P
(d) none of above
Answer is (c)

N.14)A) G1(s).G2(s)
B) G1(s)/G2(s)
C) G1(s).[1/G1(s) + G2(s)]
D) G1(s).[1/G1(s) - G2(s)]
options:
(a) all of them
(b) only C and D
(c) A, C and D
(d) B, C and D
Answer is ( )