SET - 1
R10
Code No: R22025
II B. Tech II Semester Supplementary Examinations April/May – 2013
ELECTRICAL CIRCUIT ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
A balanced ∆-connected load with phase impedance of 23.7+j 17.1 Ω at 50 Hz is supplied from
a 400 V, 50Hz balanced Y- connected source through connection impedance of 0.1+j0.3Ω in
each line.
i) Find the line current and load voltage
ii) Find the load-branch currents
iii) Find the active and reactive power delivered by the source and delivered to the load.
2.
a) Explain two wattmeter method for measurement of three phase power
b) A three phase, three-wire, 208 V, ABC systems supplies a delta-connected load where
Z AB = 5∠0 0 Ω, Z BC = 4∠30 0 Ω and Z CA = 6∠ − 15 0 Ω. Find the line currents and the
readings of watt-meters in lines A and C.
3.
a) Solve for i and v as functions of time in the circuit shown in Figure1.
10 Ω
+
10 V
-
10 Ω
t=0
10 mH
i
+
v
-
Figure 1
b) A Capacitor C is initially charged to 500 V and is left open for 120 s. The voltage across the
capacitor at the end of this time interval is seen to be 400 V. A resistor of 100 kΩ is
connected across this capacitor at 120 s. The voltage across the capacitor is found to reach
100 V in 216.4 s after this connection has been made. Find the value of C and its leakage
resistance.
4.
A sinusoidal voltage V(t) = Vm sin(wt+ϴ) is applied to a series RLC circuit at time t =0. Find
the complete solution for the current i(t) using Laplace transform method.
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5.
SET - 1
R10
Code No: R22025
a) Derive the relationship between transmission parameters and admittance parameters.
b) Find the open circuit impedance parameters for the two-port network shown in Figure 2?
1
2
10 mH
5Ω
1|
6.
10 Ω
2|
Figure 2
Determine the Y parameters of the overall network, considering two identical sections of the
network shown in Figure 3, are connected in parallel.
1Ω
+
1Ω
1Ω
+
1Ω
V1
V2
-
Figure 3
3π
3π
5π
−π
π
π
to , zero from
to
, 10 from
to
,
2
2
2
2
2
2
and so on. Find the Fourier series expansion of the wave
b) If V(t) = [10+6 cos (t + 450)+ 1.8 cos (2t-100)] V and i(t) = [3+1.4 cos (t+200)+0.5 cos2t]
mA, calculate the average power in watt. Determine also the effective voltage and effective
current.
7.
a) A square wave has a value 10 from
8.
a) Define Fourier’s transform. How does Fourier transform differ from Laplace transform?
b) Find the response voltage in the network shown in Figure 4, by using Fourier transform
method.
+
I1(t)= 5e-t u(t) A
1F
2Ω
V2
-
Figure 4
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SET - 2
R10
Code No: R22025
II B. Tech II Semester Supplementary Examinations April/May – 2013
ELECTRICAL CIRCUIT ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
A star-connected three-phase load consists of three similar impedances. When the load is
connected to a three-phase 400V, 50 Hz supply it takes 30A line current at 0.8 (Lagging) power
factor.
i) Calculate the total power taken by the load.
ii) The resistance and reactance of each phase of the load.
iii) If the power is measured by the two wattmeter method, then calculate the reading of each
wattmeter.
2.
A 3-phase, 4-wire system having a 254-V line to-neutral has the following loads connected
between the respective lines and the neutral:
Z R = 10∠0 0 Ω; Z Y = 10∠37 0 Ω;
Z B = 10∠ − 53 0 Ω;
Calculate the current in the neutral wire and the power taken by each load when the phase
sequence is
i) RYB
and
ii) RBY.
3.
a) In a series RL circuit, the application of a dc voltage results in a current of 0.741 times the
final steady-state value of current after one second. However, after the current has reached
its final value, the source is short-circuited. What would be the value of the current after
one second?
b) A series RLC circuit with R = 3Ω, L = 1H and C = 0.5 F is excited with a unit step voltage.
Obtain an expression for the current using Laplace transform. Assume that the circuit is
relaxed initially.
4.
a) What do you understand by transient and steady state response? How can they be identified
in a general solution?
b)
In
the
circuit
shown
in
Figure
1,
the
applied
voltage
is
V (t ) = 10 sin (10 t + π / 6), R = 1Ω, C = 1F . Using Laplace transformation, find complete
solution for current i(t). Switch K is closed at time t = 0. Assume zero charge across the
t=0
capacitor before switching.
K
V
~
1F
1Ω
i(t)
Figure 1
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R10
Code No: R22025
SET - 2
5.
a) The currents I1 and I2 at the input port and the output port respectively of a two-port network
are given by I1 = 6V1 – V2 and I2 = -V1 + 2V2 Find the equivalent π- network.
b) Express Z- parameters in terms of ABCD parameters.
6.
a) Two two-part networks are connected in cascade. Prove that the overall transmission
parameter matrix is the product of individual transmission parameters matrices.
b) Two identical sections of below Figure 2 are connected in series. Obtain the Z-parameters of
the resulting network.
2Ω
2Ω
1Ω
Figure 2
7.
a) Show that the Fourier series expansion of a periodic function with odd symmetry contains
only the sine terms.
b) The current in an RL Circuit with R = 12Ω, and L = 6H is i(t) = [12 sin 900t + 7 sin 2700t +
4 sin 4500t] A. Determine the effective applied voltage and average power.
8.
a) Discuss any four properties of Fourier transforms.
b) Find the Fourier transform of signum function and unit step function.
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R10
Code No: R22025
SET - 3
II B. Tech II Semester Supplementary Examinations April/May – 2013
ELECTRICAL CIRCUIT ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
a) For a ∆-connected purely resistive balanced load, sketch the phasor diagram for the load
voltages and currents. Show that the phasor sum of the load currents is zero
b) A balanced three-phase star connected load of 200 kW takes a loading current of 150 A with
a line voltage of 1200 V, 60 Hz, What are the circuit constants of the load per phase?
2.
Draw the circuit diagram of the two-wattmeter method for measuring power in a three-phase
load. Show that the sum of the meter readings equals the total power dissipated in the load,
whether the load is balanced or unbalanced, Y-connected or ∆-connected.
3.
a) Derive an expression for the decay current in an RC circuit excited by a unit step voltage.
What is the time constant of the circuit?
b) For the circuit shown in Figure 1, find the expression for transient current when the switch is
closed at t = 0.
2Ω
5V
t=0
3Ω
10 H
Figure 1
4.
a) A sinusoidal voltage of 12 sin 8t volts is applied at t=0 to a series circuit of R=4Ω and L
=1H. By Laplace transform method determine the circuit current i(t) for t ≥0. Assume zero
initial conditions.
b) An AC voltage source of v(t) = Vm sin wt is applied to a series RL circuit from t=0. The
π

circuit current is found to be i(t)=0.7 sin  wt −  A. Was there any initial current is the
3

inductor? If yes, what is its magnitude.
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SET - 3
R10
Code No: R22025
5.
a) Express ABCD parameters in terms of Z-parameters.
b) The Y-parameters for a two-port network N are given as Y11= 4 mho, Y22= 5 mho,
Y12=Y21=4 mho. If a resistor of 1Ω is connected across port-1 of N then find the output
impedance.
6.
a) Two two-port networks are connected in parallel. Prove that the overall Y-parameters are the
sum of corresponding individual Y-parameters.
b) Two identical sections of the circuit shown below Figure 2 are connected in series obtain the
Z-parameters of the combination
1 mho
I1
I
2
+
+
V1
0.2 mho
-
V2
0.5 mho
-
Figure 2
7.
a) Outline the general procedure of determining Fourier series of periodic waveform.
b) The current in an RL circuit with R=12Ω and L=6H is i(t) =12 sin 900t+7 sin2700t + 4 sin
4500 t. Determine the effective applied voltage and average power.
8.
a) Obtain the Fourier transform of signum function.
b) Determine the output voltage response across the capacitor to a current source excitation
i(t) = 5e-t u(t), as shown in Figure 3.
+
i (t)
5Ω
3F
V(t)
-
Figure 3
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SET - 4
R10
Code No: R22025
II B. Tech II Semester Supplementary Examinations April/May – 2013
ELECTRICAL CIRCUIT ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
a) Sketch the phasor diagram of line voltages, phase currents, and line currents for a balanced ∆
- connected load with Ø = 400 lagging.
b) The current coil of a wattmeter is connected in series with are of the lines of a balanced star
connected load. Whereas the pressure coil of the wattmeter is connected between other two
lines. Show that reactive power can be measured by the wattmeter with this arrangement.
2.
An unbalanced Y- connected load has a three wire supply with a line voltage of 200V and
frequency 60 Hz. The load components are R1 = R2 = R3 = 50Ω, and L3 = 398mH . Calculate
the line currents and load currents.
3.
a) Define the term ‘time constant’ of a circuit. What is the physical significance of ‘time
constant’ of a circuit? Find its value for R-L series circuit.
b) For the circuit show in Figure 1, find an expression for the current supplied by the source.
How much time it will take for the current to reach 25mA. Assume the circuit to be initially
relaxed.
t=0
10 V
500 Ω
700 Ω
100 µ F
Figure 1
4.
A series RLC circuit with R = 100 Ω, L = 0.1 H and C = 50 µF has a sinusoidal voltage source
V = 100 sin (100t+Ø). With switch being closed when Ø=900. Find the current assuming no
initial charge on the capacitor.
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5.
SET - 4
R10
Code No: R22025
a) The following equations give the voltage V1 and V2 at the two ports of a two – port network.
V1 = 5I 1 + 2 I 2 , V2 = 2 I 1 − I 2 . A load resistor of 3Ω is connected across port-2, calculate
the input impedance.
b) Currents I1 and I2 entering at port 1 and port 2, respectively of a two-port network are given
by the following equations:
I1 = 0.5 V1 − 0.2 V2
I 2 = − 0.2 V1 + V2
Where V1 and V2 are the voltage of port 1 and port 2, respectively. Find Y and ABCD
parameters of the network.
6.
a) Two – port networks N1 and N2 with series – parallel connection, where input of N2 is
connected in series with N1 and output of N2 is connected in parallel with N1. Show that
overall h – parameters are the sum of corresponding individual h – parameters.
b) Explain briefly the concept of transformed network.
7.
a) A voltage V(t) = 1000 sin (314t) + 500 sin (942t + 900) is applied to a series combination of
a resistance 100Ω and an inductor of 0.5H. Find the RMS value of v(t), i(t). Find the power
delivered to the load and hence power factor.
b) Find the trigonometric Fourier series for the half – ware rectified sine – ware shown in
Figure 2.
f(t)
V
0
ωt
3∏
2∏
∏
Figure 2
8.
a) Obtain the Fourier transform of one – sided exponential function.
b) Determine the Fourier transform of a triangular function shown in Figure 3.
f(t)
A
-T
Figure 3
T
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t
R10 – Regular Students
Code No: R22029
SET - 1
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRICAL CIRCUITS ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
A symmetrical star-connected 3-phase load is made of three identical coils each having an
internal resistance of 12Ω and inductance of 142 mH. The power taken by this load when
connected to a balanced 3-phase, 3-wire supply of 400V, 50 Hz is measured by using the two
watt-meter method. The watt-meters used are similar and are of type 400V, 5A, UPF class 1
accuracy. i) Determine the expected readings of W1 and W2 and ii) Compute the total power
2.
A balanced 3-phase system supplies an unbalanced delta connected load made of two resistors
of 100Ω and 200Ω and a coil having an inductance of 0.3H with negligible resistance. The line
to line voltage is 100V and the supply frequency is 50Hz. Calculate: i) The total power in the
system and ii) the total reactive power.
3.
A source voltage of 12 V is applied to series RL circuit at t = 0 as shown in figure 1. Using
Laplace Transform method, determine the circuit current i(t) for all t ≥ 0. Assume zero initial
conditions.
t=0
1H
12 V
+
-
3Ω
i(t)
Figure 1
4. A series RC circuit has a sinusoidal voltage source v(t ) = Vm sin(ωt + φ ) applied at time when
φ = 0 . Find the expression for current.
5.
The Z-parameters of a two-port network are Z11= 15 Ω, Z22= 25 Ω, Z12= Z21 = 5Ω. Determine
i) ABCD parameters and also ii) The equivalent T-network.
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Code No: R22029
6.
SET - 1
R10 – Regular Students
a) Synthesize the RC impedance function using Foster form I: Z ( s ) =
b) Synthesize the impedance function Z( s ) =
4( s + 2)( s + 6)
.
s (s + 4 )
( s 2 + 2 )( s 2 + 4 )
using first form of Cauer
s( s 2 + 3 )( s 2 + 5 )
network.
7.
a) Determine the Fourier series for the saw tooth function shown in Figure 2.
f(θ)
1
θ
0
2π
4π
Figure 2
b) Determine the Fourier series expansion of the functions shown in below Figure 3.
1
-T/4
0
T/2 3T/4 T
t
T/4
Figure 3
8.
Find the response voltage in the network shown in Figure 4. Use Fourier transform method.
+
i1(t)= 2e-t u(t)
1/2 F
1Ω
V2(t)
-
Figure 4
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Code No: R22029
SET - 2
R10 – Regular Students
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRICAL CIRCUITS ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
A 3-phase system referred to as the Y-Y configuration having both the sources and the loads
connected in the form of a Y. The following parameters are known:
Source voltage
VSA = 120 ∠0 0 V(rms)
Source impedance
Zg= 0.05+j0.15
Load impedance
ZLoad=4+j3
Feeder impedance
ZLine=0.1+j0.2
(i) Compute IA and VAN (ii) Without further analysis state the values of IB, IC, VBN and VCA
(iii) Find the line to line voltage VAB, VBC, and VCA (iv) Find the total average power
delivered to the loads.
2.
a) A symmetrical three-phase 100V; three-wire supply feeds an unbalanced star-connected
load, with impendence’s of the load as Z R = 5∠0 0 Ω , Z Y = 2∠90 0 Ω and
(ii) Voltage across the impedances.
Z B = 4∠ − 90 0 Ω . Find (i) Line currents
b) The two-wattmeter method produces wattmeter readings P1 =1560 W and P2 =2100 W when
connected to a delta-connected load. If the line voltage is 220 V, calculate: i) per-phase
average power, ii) per-phase reactive power, iii) phase impendence.
3.
a) In a series RL circuit, the application of a dc voltage results in a current of 0.741 times the
final steady state value of current after 1 sec. However, after the current has reached its final
value, the source is short circuited. What would be the value of the current after one second?
b) In the figure 1 shown below v(t) = 10V. Find i2(t) in the circuit. Assume all initial
conditions to be zero. Use Laplace Transform technique.
+
0.1 H
v(t)
1Ω
1/2F
i1(t)
i2(t)
2Ω
Figure 1
4.
For the circuit shown below in figure 2, determine the transient current when the switch is
moved from position 1 to 2 at t = 0. The circuit is in steady state with switch in position 1. The
voltage applied to the circuit is v(t) = 150 cos(200t+300)V.
1 t=0
200 Ω
2
v(t)
0.5 H
~
Figure 2
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1 of 2
R10 – Regular Students
Code No: R22029
5.
SET - 2
Determine the Z-parameters and Y-parameters for the network shown below Figure 3.
3Ω
1Ω
I2
I1
6Ω
3Ω
V2
V1
Figure 3
s( s 2 + 10 )
using first Foster form of realization.
( s 2 + 4 )( s 2 + 16 )
2( s + 1 )( s + 3 )
b) Synthesize the network in Cauer form I and II of the given function Z( s ) =
.
( s + 2 )( s + 4 )
6. a) Synthesize the function Z( s ) =
7.
Find the Fourier series expansion of the waveform shown below figure 4.
f(t)
1
-π
0
π
t
2π
-1
Figure 4
8.
The current source in the figure 5 is i(t)=4e-t for t 0. Find the voltage V0 using Fourier
transform method.
+
i(t)
1Ω
0.5 F
V0(t)
-
Figure 5
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Code No: R22029
SET - 3
R10 – Regular Students
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRICAL CIRCUITS ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
A balanced 3-phase star-connected load of 210 kW takes a leading current of 160A when
connected across a symmetrical 1.1 kV, 50Hz supply. Find the load circuit passive parameters
per phase.
2.
The following unbalanced star-connected impedances are connected to a 400V, three phase,
system: ZR=j30Ω, ZY=j3 Ω, and ZB = -j3 Ω, Calculate the line currents by using
i) Kirchhoff’s laws
ii) Star-Delta conversion
A coil of resistance 12 Ω and inductance of 18 H is suddenly connected to a dc supply of 30V.
calculate: (i) The initial rate of change of current (ii) ii) The time constant (iii) The current after
3s (iv) The energy stored in the magnetic field during this time (v) The energy lost as heat
during this time.
3.
4.
a) A sinusoidal voltage v(t)=25 sin10t is applied at time t = 0 to a circuit as shown below fig 1,
find the current i(t) by Laplace transform method. Take R = 5Ω and L = 1H.
t=0
L
v(t)
~
R
i(t)
Figure 1
b) A series RLC circuit, with R = 5Ω, L= 0.1H, and C = 500µF, has a sinusoidal voltage
source, V=1000 sin 250t. Derive the expression for current and the resulting current if the
switch is closed at t=0.
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5.
SET - 3
R10 – Regular Students
Code No: R22029
3s ( s + 4)
find its pole-zero plot.
( s + 2)( s 2 + s + 1)
b) Find Z parameters for the two-port shown below Figure 2.
a) A transfer function is given by Z ( s ) =
+
20 Ω
50 Ω
40 Ω
V1
+
25 Ω
V2
-
Figure 2
6.
a) Using Foster form II, synthesize the function: Y( s ) =
( s 2 + 5 )( s 2 + 13 )
s( s 2 + 9 )
b) Synthesize the following LC impedance function Z ( s ) =
s ( s 2 + 3)( s 2 + 5)
using Cauer
( s 2 + 2)( s 2 + 4)
form-II.
7.
a) Determine the Fourier series in exponential form for the function shown below in Figure 4a.
b) Find the trigonometric Fourier series of the waveform shown below in Figure 4b.
v(t)
f(t)
V
-T
-T/2
0
1
T/2
t
T
-π
0
π
t
-1
Figure 4b
Figure 4a
8.
Find the Fourier transform of the sine pulse shown in figure 5, and sketch the amplitude and
phase spectra. If this voltage is applied to a series RL circuit with R= 1 Ω an L= 1.0 H,
determine the amplitude and phase spectra for the resulting current i(t).
V(t)
A
π
0
Figure 5
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t(sec)
SET - 4
R10 – Regular Students
Code No: R22029
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRICAL CIRCUITS ANALYSIS - II
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
Three impedances ZA, ZB, and ZC are connected in delta to a 200V, 3-phase, 3-wire
symmetrical system. The phase sequence is RYB. Z A = 10∠60 0 Ω between lines R and Y;
Z B = 10∠60 0 Ω between lines B and R; and Z C = 10∠0 0 Ω between line Y and B. The total
power in the circuit is measured by means of two watt meters with their current coils in the
lines R and B and their corresponding pressure coils across R and Y and B and Y respectively.
Calculate the reading on each wattmeter and the total power supplied.
2.
A 3-phase, 3-wire CBA system supplies a ∆-connected load in which Z AB = 25∠90 0 Ω ,
Z BC = 15∠30 0 Ω , Z BC = 20∠0 0 Ω . Line voltage is 230V. Find the wattmeter reading when
the two wattmeter method is used with meters in lines A and B.
3.
A series RC circuit consists of 10Ω and capacitor of 0.1 F as shown in fig. 1. A constant
voltage of 20V is applied to the circuit at t = 0. Obtain the current equation. Determine the
t=0
voltage across the resistor and the capacitor.
0.1 F
20 V
+
-
10 Ω
i(t)
Figure 1
4.
For the circuit shown in fig. 2, determine the total current delivered by the source when the
switch is closed at t = 0. Assume no initial charge on the capacitor.
5 ohm
t=0
10e-t
+
i1(t)
i2(t)
1F
Figure 2
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10 ohm
5.
a) Calculate the Y parameters for the two-port in Figure 3a.
b) Sketch the pole-zero plots of Z11 of the network shown below Figure 3b.
4Ω
1
2
6Ω
3Ω
21
Figure 3a
1F
-
11
Figure 3b
a) Synthesize the following function in Cauer form I and II. Z( s ) =
b) Using Foster form I, synthesize the function Z( s ) =
s 3 + 2s 2 + s + 1
s3 + s2 + s
s( s 2 + 9 )
( s 2 + 5 )( s 2 + 13 )
a) Find the Fourier series of the square wave in figure 4(a). Plot the amplitude and phase
spectra.
b) Obtain the Fourier series for the periodic function in Figure 4(b) and plot the amplitude and
phase spectra.
f(t)
f (t)
1
-2
-1
0
1
1
2
3
t
-2
t
-1
0
-1
Figure 4a.
8.
1
Ω
3
V1 (t)
3Ω
11
7.
1H
1
+
6Ω
6.
SET - 4
R10 – Regular Students
Code No: R22029
1
2
Figure 4b.
a) Write the properties of Fourier transform and explain.
b) Determine the Fourier transform of the trapezoidal function shown below Figure 5.
F(t)
V
-b
a
-a
Figure 5
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b
t
3
Code No: R22043
R10
SET - 1
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRONIC CIRCUIT ANALYSIS
(Com. to ECE, EIE)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
a) Draw the circuit diagram of Common Drain amplifier and derive an expression for its
Voltage gain.
b) The h-parameters of the transistor used in CE amplifier are hfe = 50, hie =1.1K,
hre = 2.5×10-4, hoe = 24µ A/V. Find out current gain and voltage gains with and without
source resistance , input and output impedances , given that RL= 10 K and RS= 1 K
2.
a) Explain the nature of feedback in an emitter follower circuit. State the advantages of this
circuit and mention its use. Can this circuit be used as a voltage amplifier?
b) The total harmonic distortion of an amplifier is reduced from 15% to 3% when 4% negative
feedback is used. Find (i) voltage gain without feedback (ii) voltage gain with feedback?
3.
a) Describe the crystal oscillator. What is the advantage of a crystal oscillator over an LC
oscillator?
b) A tuned collector oscillator connected across the primary has a capacitance of 100pF.The
d.c resistance of the primary coil is 10 ohm and the transistor used has hie=1k ohm, hre=10-4,
hfe=50 and hoe=10-4 A/V. Find the frequency of oscillation and the mutual inductance
between the primary and secondary coils required to sustain the oscillations ?
4.
a) Draw the circuit of two stages R-C coupled JFET amplifier and explain its working.
b) Draw the circuit diagram of single stage R-C coupled BJT amplifier. Discuss the effect of an
emitter bypass capacitor on low-frequency response.
5.
a) Derive the expression for the CE short circuit current gain Ai as a function of frequency
using Hybrid - π model.
b) A single-stage CE amplifier is measured to have a voltage - gain bandwidth fH of 5 MHz
with RL = 500. Assume hfe = 100, gm=100 mA/V, rbb′ = 100, Cc = 1pF, and fT = 400 MHz.
Find the value of the source resistance that will give the required bandwidth.
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Code No: R22043
R10
SET - 1
6.
a) Classify large signal amplifiers based on its operating point. Distinguish these amplifiers in
terms of the conversion efficiency.
b) Draw the push-pull power amplifier circuit. Derive the expression for the output current in
push- pull amplifier with base current as Ib = Ibm sinωt.
7.
a) Draw the circuit diagram of a Double tuned amplifier. Draw and explain in detail the
frequency response for different values of coefficient of coupling (K) i.e. K=1, K= 1.5, K=2
and also explain what is Loose coupling and Tight coupling?
b) What is synchronous tuning? Derive an expression for bandwidth of an n-stage
synchronously tuned amplifier?
8.
a) The voltage regulator in Figure 8 maintains an output voltage of 25 V.
i) What value of Rsc should be used to limit the maximum current to 0.5A?
ii) With the value of Rsc found in (i) what will be the output voltage when RL= 100 ohms?
b) What type of protection circuits are required in power supplies?
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Code No: R22043
R10
SET - 2
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRONIC CIRCUIT ANALYSIS
(Com. to ECE, EIE)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
a) Discuss the classification of amplifiers based on frequency range, type of coupling, power
delivered, and signal handled.
b) The h-parameters of a transistor are hfe = 50, hie = 1.1K, hre = 2.5x10-4, hoe = 24 µA/V
Calculate AI, AV, AVS, Ri, and Ro for Figure 1b
2.
a) Explain the effects of negative feedback on amplifier characterisitcs?
b) An amplifier having a gain of 500 without feedback has an overall negative feedback
applied which reduces the gain to 100.Calculate the fraction of output voltage feedback? If
due to ageing of components, the gain without feedback falls by 20% calculate the
percentage fall in gain with feedback?
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Code No: R22043
R10
SET - 2
3.
a) Describe the circuit diagram of Colpitt’s oscillator and explain its operation?
b) A Hartley oscillator is to span a frequency range from 50 KHz to 150 KHz. The variable
capacitance has the values in the range 50 pF to 450 pF. The transistor to be used has hfe=50
and ∆h = 0.5. Determine the values of the inductances. Neglect mutual inductance between
the coils and use CE circuit configuration.
4.
a) Differentiate between direct and capacitive coupling of multiple stages of amplifiers.
b) With the help of a neat circuit diagram, describe the working of a Cascode amplifier
5.
a) Explain how hybrid Π parameters, gm and gce vary with Ic, Vce and temperature.
b) Discuss the effect of different type of loads to a common source MOS amplifier.
6.
a) A single stage class A amplifier Vcc=20V, VCEQ =10V, ICQ =600 mA, RL=16 Ω. The ac
output
current varies by 300mA, with the ac input signal. Find
i) The power supplied by the dc source to the amplifier circuit.
ii) AC power consumed by the load resistor.
iii) AC power developed across the load resistor.
iv) DC power wasted in transistor collector.
v) Overall efficiency
b) What are the drawbacks of transformer coupled power amplifiers?
7.
a) Derive an expression for bandwidth of a capacitive coupled tuned amplifier in CE
configuration. Make necessary assumptions and mention them
b) Discuss the necessity of stabilization circuits in tuned amplifiers
8.
a) Explain different types of protections required in IC Voltage Regulators.
b) Draw and explain the output of pulse width modulator for different types of inputs with
respect to switching regulator.
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Code No: R22043
R10
SET - 3
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRONIC CIRCUIT ANALYSIS
(Com. to ECE, EIE)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
a) State Miller's theorem. Explain its significance in transistor circuit analysis.
b) For the Common Gate amplifier shown below Figure 1, derive expressions for voltage gain,
input impedance and output impedance. Power supplies are omitted for simplicity. Neglect
capacitances.
2.
a) If the non-linear distortion in a negative feedback amplifier with an open loop gain of 100 is
reduced from 40% to 10%with feedback, compute the feedback factor, β of the amplifier.
b) Draw the circuit diagram of a current series feedback amplifier, Derive expressions to show
the effect of negative feedback on input & output impedances, bandwidth, distortion of the
amplifier.
3.
a) Derive the expression for frequency of oscillation in a Hartley Oscillator.
b) With the help of suitable schematic and description, show that both positive and negative
feedback are used in a Wien Bridge oscillator. Establish the condition for oscillations
4.
a) The gain of an RC coupled 2 stage FET amplifier falls by 90% of the mid band value at 400
kHz. If gm of each FET is 10 m A/V, and total output capacitance for each stage is 20 pF,
calculate the RL required and the mid band gain of each stage
b) Write a short note on Bandwidth of amplifiers.
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Code No: R22043
R10
SET - 3
5.
a) What are the typical values of various components in Hybrid - π model? Show that at low
frequencies the Hybrid - π model with rb′e and rce taken as infinite reduces to the
approximate CE h- parameter model.
b) The following low- frequency parameters are known for a given transistor at IC = 10mA,
VCE =10 V, and at room temperature, hie = 500, hoe = 4x10−5 A/V, hfe = 100, hre = 10−4.
At the same operating point, fT = 50MHz and Cc=3pF, compute the values of all the Hybrid - π
parameters
6.
a) What is Harmonic distortion in transistor amplifier circuits? Discuss second harmonic
distortion.
b) A single transistor is operating as an ideal class B amplifier with a 500 load. A dc meter in
the collector circuit reads 10 mA. How much signal power is delivered to the load?
7.
a) What is synchronous tuning? Derive an expression for bandwidth of an n-stage
synchronously tuned amplifier?
b) Show that for an ’n’ stage synchronously tuned amplifier; maximum bandwidth is obtained
when the single stage gain is 4.34 dB.
8.
a) Draw the functional block diagram of Series Voltage Regulator and explain each block.
b) A 50V power supply has line regulation 0.2%V. How large would the 75V input voltage to
the supply have to become for the output voltage to rise to 52V?
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Code No: R22043
R10
SET - 4
II B. Tech II Semester Regular Examinations April/May – 2013
ELECTRONIC CIRCUIT ANALYSIS
(Com. to ECE, EIE)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
~~~~~~~~~~~~~~~~~~~~~~~~
1.
a) Sketch the circuit of a Common Source amplifier. Derive an expression for the Voltage gain
at low frequencies. What is the maximum value of AV.
b) Calculate the voltage gain AV = Vo/Vi at 1 KHz for the circuit shown in 1b.The FET
parameters are gm=2 mA and rd=10K. Neglect capacitances. If the capacitance 0.003F is
also considered, calculate the voltage gain.
2.
a) The β and the open loop gain of an amplifier are -10% and -80 respectively. By how
much % the closed loop gain changes if the open loop gain increases by 25%?
b) With the help of a suitable BJT based voltage series feedback amplifier diagram, explain the
features and benefits of negative feedback in amplifiers.
3.
a) With the help of neat circuit diagram, explain how sustained oscillations are obtained in RC
phase shift BJT based oscillator. Derive the expression for frequency of oscillation.
b) Differentiate between LC and RC oscillators?
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SET - 4
R10
Code No: R22043
4.
a) List out the special features of Darlington pair and Cascode amplifiers
b) A two-stage amplifier circuit (CE-CC configuration) is shown in figure 4b. The h-parameter
values are hfe = 50, hie=2 K , hre =6× 10−4, hoe = 25µA/V. hfc = -51, hic =2 K, hrc = 1,
hoc = 25µ A/V. Find the input and output impedances and individual, as well as overall
voltage and current gains.
5.
a) A transistor amplifier in CE configuration is operated at high frequency with the following
specifications. f =6MHz, g =0.04, h =50, r =100 Ω, R =500 Ω , C =10 pF, R =100 Ω.
T
m
fe
bb’
s
b’c
L
Compute the voltage gain, upper 3dB cut-off frequency, and gain bandwidth product.
b) Derive the expression for the CE short circuit current gain AI as a function of frequency
using Hybrid - π model.
6.
a) Write short notes on requirement and types of heat sinks for power dissipation in large signal
amplifiers.
b) With the help of a neat circuit diagram, explain the operation of a complementary symmetry
configured class B power amplifier.
c) A push pull amplifier utilizes a transformer whose primary has a total of 160 turns and
whose secondary has 40 turns. It must be capable of delivering 40W to an 8 Ω load under
maximum power conditions. What is the minimum possible value of Vcc?
7.
a) Draw the circuit diagram and small signal AC equivalent circuit of a single tuned amplifier
(using BJT) with the tank circuit connected at the input side.
b) With a neat diagram show how to cascade tuned amplifiers and determine gain and band
width?
8.
a) What type of protection circuits are required in power supplies?
b) A 50V power supply has line regulation 0.2%V. How large would the 75V input voltage to
the supply have to become for the output voltage to rise to 52V?
c) Give the disadvantages of the series and shunt regulators.
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Set No. 1
Code No: V0401/R05
II B.Tech II Semester Supplementary Examinations, Apr/May 2013
ELECTRICAL TECHNOLOGY
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
?????
1. (a) Draw circuit diagrams the following types of D.C. Generators
i. Shunt
ii. Series and
iii. Compound
(b) State with reason the area of application of various D.C. Generators used?
(c) The induced emf in DC machine while running at 750 rpm is 220V.
i. Assuming constant flux/pole calculate the speed at which the induced emf
will be 250V.
ii. The percentage increase in the field flux for an induced emf of 250V and
speed of 700rpm.
[3+5+8]
2. (a) Explain the various losses occurring in a DC machine.
(b) Derive the conditions for maximum efficiency of a DC motor.
(c) A 250V, 4 pole, shunt motor has two circuit armature winding with 500 conductors. The armature circuit resistance is 0.25 Ω, field resistance is 125 Ω
and the flux per pole is 0.02Wb. Armature reaction is neglected. If the motor
draws 14A from the mains, then compute
i. speed and the internal torque developed.
ii. The shaft power, shaft torque and efficiency with rotational losses equals
to 300W.
[4+4+8]
3. Draw the phasor diagrams of a transformer at no load and full load lagging power
factor conditions and explain the operation of a transformer.
[16]
4. (a) Out line the tests that can be conducted on a transformer to obtain losses for
the calculation of efficiency.
(b) A 5 KVA 2000/250 Volts single phase transformer gave the following test
results:
Open circuit test : 250 V, 0.8 A, 50 W
Short circuit test: 60V 3A 45 W
Calculate efficiency at full load and half full load 0.8 power factor lag. [8+8]
5. (a) Show that when a 3-phase supply is given to the stator winding of Induction Motor, it produces a rotating magnetic field of constant magnitude and
rotating at synchronous speed.
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Set No. 1
Code No: V0401/R05
(b) A 12-pole, 3-phase Induction Motor is fed from 100Hz supply. If the frequency
of rotor e.m.f at full load is 5 Hz, find the Full-Load speed and %Slip. [12+4]
6. (a) Explain the constructional features of alternator.
(b) How e.m.f is induced in an 3-phase alternator? Derive the expression for e.m.f
induced in an alternator in terms of pitch and distribution factors.
[8+8]
7. Explain the constructional features and principle operation of a single phase induction motor.
[16]
8. With a neat sketch explain in detail moving iron repulsion type instrument
?????
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[16]