### Network Synthesis & Driving Point Impedance - Topicwise GATE Questions on Network Theory (from 2003)

2005
1. The first and Last critical frequency of an RC driving point impedance function must respectively be
a) a zero and a pole
b) a zero and a zero
c) a pole and a pole
d) a pole and a zero

2006
2. The first and the last critical frequencies (singularities) of a driving point impedance function of a passive network having two kinds of elements, are a pole and a zero respectively. The above property will be satisfied by
a) RL network only
b) RC network only
c) LC network only
d) RC as well as RL networks

3. A negative resistance Rneg is connected to a passive network N having driving point impedance Z1(s) as shown below. For Z2(s) to be positive real,

2008
4. The driving point impedance of the following network is given as shown. The component values are

### Steady State Analysis of AC and DC circuits - Topicwise GATE Questions on Network Theory (from 2003)

2005
1. For the circuit in figure, the instantaneous current i1(t) is

2007
2. In the AC network shown in the figure, the phasor voltage VAB(in volts) is:

2008
Common Data Questions: 3 & 4
The following series RLC circuit with zero initial conditions is excited by a unit impulse function δ(t).

3. For t > 0, the output voltage Vc(t) is

4. For t > 0, the voltage across the resistor is

Solution (3 & 4) : https://www.youtube.com/watch?v=nn6PggFjKgA

2009
5. The time domain behaviour of an RL circuit is represented as shown below. For an initial current of i(0) = Vo/R, the steady state value of the current is given by

2010
6. The current I in the circuit shown is

a) - j1 A
b) j1 A
c) 0 A
d) 20 A

2011
7. In the circuit shown below, the Norton equivalent current in amperes with respect to the terminals P and Q is

a) 6.4 - j 4.8
b) 6.56 - j 7.87
c) 10 + j 0
d) 16 + j 0

8. The circuit shown below is driven by a sinusoidal input Vi = Vpcos(t/RC). The steady state output Vo is

9. In the circuit shown below, the current I is equal to

2012
10. In the circuit shown below, the current through the inductor is

2014
11. In the circuit shown in the figure, the value of node voltage V2 (in volts) is

a) 22 + j 2
b) 2 + j 22
c) 22 – j 2
d) 2 – j 22

12. The steady state output of the circuit shown in the figure is given by y(t) = A(ω) sin(ωt + φ(ω)).

If the amplitude |A(ω)| = 0.25, then the frequency ω is

13. In the circuit shown in the figure,

the value of Vo(t) (in volts) for t → ∞ is ___________

2015
14. In the circuit shown, assume that diodes D1 and D2 are ideal. In the steady state condition, the average voltage Vab (in volts) across 0.5 µF capacitor is ____________

### Resonance (Series and Parallel) - Topicwise GATE Questions on Network Theory (from 2003)

2003
1. A series RLC circuit has a resonance frequency of 1 kHz and a quality factor Q = 100. If each R, L and C is doubled from its original value, the new Q-factor of the circuit is
a) 25
b) 50
c) 100
d) 200

2004
2. Consider the following statements S1 and S2
S1: at the resonant frequency, the impedance of a series RLC circuit is zero.
S2: In a parallel G-L-C circuit, increasing the conductance G results in increase in its Q-factor.
Which one of the following is correct?
a) S1 is FALSE and S2 is TRUE
b) Both S1 and S2 are TRUE
c) S1 is TRUE and S2 is FALSE
d) Both S1 and S2 are FALSE

2005
3. The condition on R, L and C such that the step response y(t) in figure has no oscillations, is

4. In a series RLC circuit, R = 2 kΩ, L = 1 H, and C = 1/400 µF. The resonant frequency is
a) 2 x 104 Hz
b) (1/π) x 104 Hz
c) 104 Hz
d) 2π x 104 Hz

2007
5. Two series resonant filters are as shown in the figure. Let the 3-dB bandwidth of filter 1 is B1 and that of Filter 2 is B2. The value of B1/B2 is

a) 4
b) 1
c) 1/2
d) 1/4

2010
6. For parallel RLC circuit, which one of the following statements is NOT correct?
a) The bandwidth of the circuit decreases if R is increased
b) The bandwidth of the circuit remains same if L is increased
c) At resonance, input impedance is a real quantity
d) At resonance, the magnitude of input impedance attains its minimum value.

2013
7. Two magnetically uncoupled inductive coils have Q factors q1 and q2 at the chosen operating frequency. Their respective resistances are R1 and R2. When connected in series, their effective Q factor at the same operating frequency is
a) q1 + q2
b) (1/q1) + (1/q2)
c) (q1R1 + q2R2) / (R1 + R2)
d) (q1R2 + q2R1) / (R1 + R2)

2014
8. In the circuit shown in the figure, the value of capacitor C (in mF) needed to have critically damped response i(t) is ____________________

9. A series LCR circuit is operated at a frequency different from its resonant frequency. The operating frequency is such that the current leads the supply voltage. The magnitude of current is half the value at resonance. If the values of L, C and R are 1H, 1F and 1Ω respectively, then the operating angular frequency (in rad/sec) is ____________________

10. In the circuit shown in the figure, the angular frequency ω (in rad/sec), at which the Norton equivalent impedance as seen from terminals b – b' is purely resistive, is _____________

2015
11. In the circuit shown, at resonance, the amplitude of the sinusoidal voltage (in volts) across the capacitor is ____________________

12. The voltage (Vc) across the capacitor (in volts) in the network shown is ______________

13. An LC tank circuit consists of an ideal capacitor C connected in parallel with a coil of inductance L having an internal resistance R. The resonant frequency of the tank circuit is

14. In the circuit shown, the current I flowing through the 50 Ω resistor will be zero, if the value of the capacitor C (in µF) is __________________

### Network Topology and Mutual Inductance - Topicwise GATE Questions on Network Theory (from 2003)

2003
1. The current flowing through the resistance R in the circuit shown has the form Pcos4t, where p is

a) (0.18 + j0.72)
b) (0.46 + j1.90)
c) - (0.18 + j1.90)
d) - (0.192 + j0.144)

Answer: Data is insufficient as inductor values are not given in the figure.

2004
2. Consider the network graph shown in figure. Which one of the following is NOT a ‘tree’ of this group?

3. The equivalent inductance measured between the terminals 1 and 2 for the circuit shown in figure, is

a) L1 + L2 + M
b) L1 + L2 - M
c) L1 + L2 + 2M
d) L1 + L2 - 2M

2005
4. Impedance Z as shown in figure is

a) j29 Ω
b) j9 Ω
c) j19 Ω
d) j39 Ω

2008
5. In the following graph, the number of trees (P) and the number of cut-sets (Q) are

a) P = 2, Q = 2
b) P = 2, Q = 6
c) P = 4, Q = 6
d) P = 4, Q = 10

2013
6. The following arrangement consists of an ideal transformer and an attenuator which attenuates by a factor of 0.8. An ac voltage VWX1 = 100 volts is applied across WX to get an open circuit voltage VYZ1 across YZ. Next, an ac voltage VYZ2 = 100 volts is applied across YZ to get an open circuit voltage VWX2 across WX. Then VYZ1/VWX1, VWX2/VYZ2 are respectively

2014
7. In the magnetically coupled circuit shown in the figure, 56% of the total flux emanating from one coil links the other coil.

The value of the mutual inductance (in H) is _________________

### Two-Port Networks - Topicwise GATE Questions on Network Theory (from 2003)

2003
1. The impedance parameters Z11 and Z12 of the two port network in figure are

2004
2. For the lattice circuit shown in figure, Za = j2Ω and Zb = 2Ω. The values of the open circuit impedance parameters (Z-parameters) are

2005
3. The ABCD parameters of an ideal n:1 transformer shown in figure are given below. The value of 'x' will be

a) n
b) 1/n
c) n2
d) 1/n2

4. The h-parameters of the circuit shown in figure are

2006
5. A two port network is represented by ABCD parameters as shown below. If port-2 is terminated by RL, the input impedance seen at port-1 is given by

6. In the two port network shown in the figure below, Z12 and Z21 are respectively

2008
A two port network shown below is excited by external DC sources. The voltages and the currents are measured with voltmeters V1, V2 and ammeters A1, A2 (all assumed to be ideal), as indicated. Under following switch conditions, the readings obtained are:

7. The Z-parameter matrix for this network is

8. The h-parameter network for this network is

2010
9. For the two-port network shown below, the short-circuit admittance parameter matrix is

2011
10. In the circuit shown below, the network N is described by the following Y matrix: The voltage gain V2/V1 is

a) 1/90
b) - 1/90
c) - 1/99
d) - 1/11

2012
Common Data for Questions 11 and 12:
With 10 volts DC connected at port A in the linear nonreciprocal two-port network shown below,

the following were observed:
(i) 1Ω connected at port B draws a current of 3 amps
(ii) 2.5Ω connected at port B draws a current of 2 amps
11. With 10 volts DC connected at port A, the current drawn by 7Ω connected at port B is
a) 3/7 A
b) 5/7 A
c) 1 A
d) 9/7 A

12. For the same network, with 6 volts DC connected at port A, 1Ω connected at port B draws 7/3 amp. If 8 volts DC is connected to port A, the open circuit voltage at port B is
a) 6 V
b) 7 V
c) 8 V
d) 9 V

2014
13. In the h – parameter model of 2 – port network given in the figure shown,

the value of h22 (in siemens) is _____________

14. For the two – port network shown in the figure,
the impedance (Z) matrix (in Ω) is

2015
15. The 2 – port Admittance matrix of the circuit shown is given by____________

16. The ABCD parameters of the following 2 – port network are

### Transient Analysis of AC and DC circuits - Topicwise GATE Questions on Network Theory (from 2003)

2003
Common circuit for Questions 1 & 2:
Assume that the switch S is in position 1 for a long time and thrown to position 2 at t=0.

1. At t = 0+, the current i1 is
a) – V/2R
b) – V/R
c) – V/4R
d) Zero

2. I1(s) and I2(s) are the Laplace Transforms of i1(t) and i2(t) respectively. The equations for the loop currents I1(s) and I2(s) for the same circuit shown, after the switch is brought from position 1 to position 2 at t = 0, are

2008
3. In the following cirucit, the switch S is closed at t = 0. The rate of change of current di(0+)/dt is given by

2009
4. The switch in the circuit shown was on position 'a' for a long time, and is moved to position 'b' at time t=0. The current i(t) for t > 0 is given by

2010
5. In the cirucit shown, the switch S is open for a long time and is closed at t = 0. The current i(t) for t ≥ 0+ is

2011
6. In the circuit shown below, the initial charge on the capacitor is 2.5 mC, with the voltage polarity as indicated. The switch is closed at time t = 0. The current i(t) at a time t after the switch is closed is

2014
7. In the figure shown, the ideal switch has been open for a long time.

If it is closed at t = 0, then the magnitude of the current (in mA) through the 4 kΩ resistor at t = 0+ is ____________

2015
8. In the circuit shown, the switch SW is thrown from position A to position B at time t=0. The energy (in µJ) taken from the 3 volts source to charge the 0.1 µF capacitor from 0 volts to 3 volts is

a) 0.3
b) 0.45
c) 0.9
d) 3