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Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE) PDF Download

Q21: Assuming an ideal transformer, the Thevenin's equivalent voltage and impedance as seen from the terminals x and y for the circuit in figure are     (SET-2 (2014))
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 2sin(ωt), 4Ω
(b) 1𝑠𝑖𝑛(𝜔𝑡),1Ω1sin(ωt), 1Ω
(c) 1𝑠𝑖𝑛(𝜔𝑡),2Ω1sin(ωt), 2Ω
(d) 2sin(ωt), 0.5Ω
Ans:
(a)
Sol: Thevenin's equivalent voltage = voltage referred to secondary.
We have: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
VTh = 2sin(ωt)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Also, Thevenin's impedance seen from the x and y terminals = voltage referred to secondary side
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q22: In the circuit shown below, if the source voltage V= 100∠53.13°V then the Thevenin's equivalent voltage in Volts as seen by the load resistance RL is       (2013)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 100 ∠ 90°
(b) 8000800 ∠ 0°
(c) 800 ∠ 90
(d) 10060100 ∠ 60 
Ans:
(c)
Sol: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q23: A source vs(t) = Vcos 100πt has an internal impedance of (4 + j3)Ω. If a purely resistive load connected to this source has to extract the maximum power out of the source, its value in Ω should be       (2013)
(a) 3
(b) 4
(c) 5
(d) 7
Ans:
(c)
Sol: Using maximum power transfer theorem,
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q24: Assuming both the voltage sources are in phase, the value of R for which maximum power is transferred from circuit A to circuit B is     (2012)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 0.8 Ω
(b) 1.4 Ω
(c) 2 Ω
(d) 2.8 Ω
Ans:
(a)
Sol: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Power transferred from circuit A to circuit B
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q25: The impedance looking into nodes 1 and 2 in the given circuit is    (2012)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 50 Ω
(b) 100 Ω
(c) 5 kΩ
(d) 10.1 kΩ
Ans: 
(a)
Sol: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)To find thevenin impedance across node 1 and node 2. Connect a 1 V source and find the current through voltage source.
Then, ZTh = 1/(ITh)
By applying KCL at node B and A
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)By applying KVL in outer loop
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)∴ From equation (i),
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q26: In the circuit given below, the value of R required for the transfer of maximum power to the load having a resistance of 3 Ω is      (2011)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) zero
(b) 3Ω
(c) 6Ω
(d) infinity
Ans:
(a)
Sol: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)For maximum power transfer to the load, the source resistance must be minimum i.e. zero.
So, R = 0Ω.

Q27:  Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)For the circuit given above, the Thevenin's voltage across the terminals A and B is     (2009)
(a) 1.25V
(b) 0.25V
(c) 1V
(d) 0.5V
Ans:
(d)
Sol: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)To calculate thevenin's volatage, terminal A-B are kept open.
Applying source transformation, voltage sorce is transformed into current source.
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Applying source transformation current source is transformed into voltage souce.
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Applying KVL, (I is assumed to be in mA)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Put value of I in equation (i),
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q28: Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)For the circuit given above, the Thevenin's resistance across the terminals A and B is      (2009)
(a) 0.5 kΩ
(b) 0.2 kΩ
(c) 1 kΩ
(d) 0.11 kΩ
Ans:
(b)
Sol: To calculate thevenin's resistance 5 V source is short-circuited and Vdc source is connected at terminals A and B
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)VAB = Vdc and assuming I and I1 in mA. Current through 1kΩ resistance
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Comparing equation (i) and (ii),
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q29: The Thevenin's equivalent of a circuit operation at ω = 5 rads/s, has Voc = 3.71∠ − 15.9° V and Z= 2.38 − j0.667Ω. At this frequency, the minimal realization of the Thevenin's impedance will have a       (2008)
(a) resistor and a capacitor and an inductor
(b) resistor and a capacitor
(c) resistor and an inductor
(d) capacitor and an inductor
Ans: 
(b)
Sol: Thevenin's Impedance:
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)as real part is not zero, so Z0 has resistor
Img[Z0] = −j0.667  
CASE-I:
Z0 has capacitor (as Img[Z0] is negative)
CASE-II:
Z0 has both capacitor and inductor, but inductive reactance < capacitive reactance.  
At, ω = 5 rad/sec
For minimal realization case-I is considered. Therefore, Zwill have a resistor and a capacitor.

Q30: In the figure the current source is 1 ∠ 0 A, R = 1 Ω, the impedances are Z= −jΩ and ZL= 2jΩ. The Thevenin equivalent looking into the circuit across X-Y is      (2006)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
(a) Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
(b) Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
 (c) Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
(d) Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Ans: (d)
Sol: To calculate Thevenin's impedance, current-souce is open-circuited
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Open-circuit voltage at terminals X - Y
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q31: In the given figure, the Thevenin's equivalent pair (voltage, impedance), as seen at the terminals P-Q, is given by     (2005)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) (2V, 5Ω)
(b) (2V, 7.5Ω)
(c) (4V, 5Ω)
(d) (4V, 7.5Ω)
Ans
: (a)
Sol: To calculate Rth (seen at terminals P-Q), voltage source is short-circuit
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Vth  = open-circuit voltage at terminals P-Q.
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Thevenin's equivalent circuit
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q32: Two ac sources feed a common variable resistive load as shown in figure. Under the maximum power transfer condition, the power absorbed by the load resistance RL is    (2003)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 2200 W
(b) 1250 W
(c) 1000 W
(d) 625 W
Ans: 
(d)
Sol: For obtaining power absorbed by RL under maximum power transfer condition. We find thevenin's equivalent circuit across RL.
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Zth is calculated by short-circuting the voltage source.
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)For maximum power transfer ,
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Power absorbed by RL(max)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q33: In the figure, Z= 10∠ − 60°, Z= 10∠60°, Z3 = 50∠53.13°.  The venin impedance seen form X-Y is      (2003)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 56.66 ∠ 45°
(b) 60 ∠ 30°
(c) 70 ∠ 30°
(d) 34.46534.4 ∠ 65°
Ans: 
(a)
Sol: By Thevenin's theorem
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)
Q34: In the circuit shown in figure, the switch is closed at time t = 0. The steady state value of the voltage Vc is      (2002)
Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE)(a) 0 V
(b) 10 V
(c) 5 V
(d) 2.5 V
Ans:
(c)

Q35: A 240 V single-phase ac source is connected to a load with an impedance of 10∠60°Ω. A capacitor is connected in parallel with the load. If the capacitor supplies 1250 VAR, the real power supplied by the source is       (2001)
(a) 3600 W
(b) 2880 W
(c) 2400 W
(d) 1200 W
Ans:
(b)

The document Previous Year Questions- Network Theorems - 2 | Network Theory (Electric Circuits) - Electrical Engineering (EE) is a part of the Electrical Engineering (EE) Course Network Theory (Electric Circuits).
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FAQs on Previous Year Questions- Network Theorems - 2 - Network Theory (Electric Circuits) - Electrical Engineering (EE)

1. What is a network theorem?
Ans. A network theorem is a rule or principle that can be used to analyze and simplify electrical circuits.
2. What are some common network theorems used in circuit analysis?
Ans. Some common network theorems include Ohm's Law, Kirchhoff's Laws, Thevenin's Theorem, Norton's Theorem, and Superposition Theorem.
3. How is Thevenin's Theorem used in circuit analysis?
Ans. Thevenin's Theorem states that any linear electrical network can be replaced by an equivalent circuit consisting of a single voltage source in series with a single resistor. This simplifies the analysis of complex circuits.
4. What is Norton's Theorem and how is it different from Thevenin's Theorem?
Ans. Norton's Theorem is another method used to simplify complex circuits. It states that any linear electrical network can be replaced by an equivalent circuit consisting of a single current source in parallel with a single resistor. The main difference between Norton's Theorem and Thevenin's Theorem is the way the equivalent circuits are represented.
5. How can network theorems be used to analyze and solve circuit problems?
Ans. Network theorems provide a systematic approach to analyzing and solving circuit problems by simplifying complex circuits into equivalent circuits that are easier to work with. By applying these theorems, engineers can analyze circuits more efficiently and accurately.
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