Download 2012

Set No. 1
Code No: Z0222/R07
I B.Tech Supplementary Examinations, December 2012
ELECTRICAL CIRCUITS ANALYSIS
( Common to Electrical & Electronics Engineering and Instrumentation &
Control Engineering)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
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1. (a) A bridge network ABCD is arranged as follows:
Resistance between terminals AB, BC, CD, DA and BD are 10 ohms, 30 ohms,
15 ohms, 20 ohms and 40 ohms respectively. A 4V battery is connected with
negligible internal resistance between terminals A and C. Determine the current through each element in the network using network reduction techniques.
(b) Three equal resistances are available. Find
i. Two ratios of the equivalent resistances when they are connected in parallel.
ii. The ratio of the current through each elements when they are connected
in parallel.
[10+6]
2. The mean diameter of a steel ring is 40cm and flux density of 0.9 wb/m2 is produced
by 3500 ampere turns per metre. If the cross-section of the ring be 15 cm2 and the
number of turns 440, calculate
(a) The exciting current,
(b) The self inductance
(c) The exciting current and the inductance when an air gap of 2cm is cut in the
ring, the flux density being the same. Ignore leakage and fringing.
[16]
3. Calculate the form factor and peak factor of a triangular wave in which the voltage
rises uniformly from 0 to V volts in time T seconds and completes the cycle by
falling instantly back to zero.
[16]
4. A three phase, 4 wire, 400V, 50Hz system supplies a load of 50KW at a power factor
of 0.75 lagging between the red phase and neutral; 60KW at a power factor of 0.85
leading between the yellow phase and neutral and 70KW at unity power factor
between the blue phase and neutral. Find the current in the neutral conductor.
[16]
5. Determine the power dissipated in the resistors in the circuit as shown in figure 5.
[16]
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Set No. 1
Code No: Z0222/R07
Figure 5
6. (a) Using Norton’s theorem, find the current through the load impedance ZL as
shown in figure 6a.
Figure 6a
(b) State and explain reciprocity theorem.
[10+6]
7. A resistance of 2ohms and a capacitor of 1 F are in series. An alternating voltage
V(t) = 2 sin (t + φ) is supplying suddenly. Find an expression for the voltage
across the capacitor.
[16]
8. For the two port n/w shown in the figure 8, the currents I1 and I2 entering at port
1 and 2 respectively are given by the equations.
I1 = 0.5 V1 - 0.2 V2
I2 = - 0.2V1 + V2
Figure 8
Where V1 and V2 are the port voltages at port 1 and 2 respectively. Find the Y, Z,
ABCD parameters for the n/w. Also find its equivalent π network.
[16]
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Set No. 1
Code No: Z0222/R07
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Set No. 2
Code No: Z0222/R07
I B.Tech Supplementary Examinations, December 2012
ELECTRICAL CIRCUITS ANALYSIS
( Common to Electrical & Electronics Engineering and Instrumentation &
Control Engineering)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆⋆⋆⋆⋆
1. (a) A bridge network ABCD is arranged as follows:
Resistance between terminals AB, BC, CD, DA and BD are 10 ohms, 30 ohms,
15 ohms, 20 ohms and 40 ohms respectively. A 4V battery is connected with
negligible internal resistance between terminals A and C. Determine the current through each element in the network using network reduction techniques.
(b) Three equal resistances are available. Find
i. Two ratios of the equivalent resistances when they are connected in parallel.
ii. The ratio of the current through each elements when they are connected
in parallel.
[10+6]
2. (a) A steel ring 10cm radius and of circular cross-section 1cm in radius has an air
gap of 1mm length. It is wound uniformly with 500 turns of wire carrying a
current of 3A. Neglect magnetic leakage. The airgap takes 60% of the total
mmf. Find the total reluctance.
(b) A coil of 500 turns and resistance 20 ohm is wound uniformly on an iron ring
of mean circumference 50cm and cross-sectional area 4cm2, it is connected to
a 24V d.c. supply. Under these conditions, the relative permeability of iron is
800. Calculate the values of
i. The magneto motive force of the coil. ii.
The magnetising force.
iii. The total flux in the iron.
iv. The reluctance of the ring.
[6+10]
3. (a) Compare series and parallel resonant circuits.
(b) A series RLC circuit consists of resistor of 100 Ω, an inductor of 0.318H and
a capacitor of unknown value. When this circuit is energised by a 230V, 50Hz
ac supply, the current was found to be 23A. Find the value of capacitor and
the total power consumed.
[4+12]
4. (a) Three identical impedances of (3+j4)Ω are connected in delta. Find an equivalent star network such that the line current is the same when connected to
the same supply.
(b) Three impedances of (7+j4)Ω, (3+j2)Ω and (9+j2)Ω are connected between
neutral and the R, Y and B phases. The line voltage is 440V, Calculate.
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Set No. 2
Code No: Z0222/R07
i. The line currents and
ii. The current in the neutral wire.
iii. Find the power consumed in each phase and the total power drawn by
the circuit.
[4+12]
5. (a) For the oriented graph shown in figure 5a. Draw tree and co-tree. Write the
cut-set matrix.
Figure 5a
(b) For the given circuit, use nodal analysis to find the current delivered by 24V
source as shown in figure 5b.
[6+10]
Figure 5b
6. (a) Using Norton’s theorem, find the current through the load impedance ZL as
shown in figure 6a.
Figure 6a
(b) State and explain reciprocity theorem.
[10+6]
7. In the circuit shown in figure 7, Eg = 2.5 Volts. What are the values of i(t) and
[16]
VL(t) at t = 4 seconds.
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Set No. 2
Code No: Z0222/R07
Figure 7
8. (a) Find the Y parameters of the pie shown in figure 8a:
Figure 8a
(b) Find the Z parameters of the T- network shown in figure 8b. Verify the
network is reciprocal or not.
[4+12]
Figure 8b
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Set No. 3
Code No: Z0222/R07
I B.Tech Supplementary Examinations, December 2012
ELECTRICAL CIRCUITS ANALYSIS
( Common to Electrical & Electronics Engineering and Instrumentation &
Control Engineering)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆⋆⋆⋆⋆
1. (a) Calculate the source current for the network as shown in figure 1a using stardelta transformation.
Figure 1a
(b) Derive an expression to convert a given 3-phase star connected circuit to delta
connetion.
[8+8]
2. Two long single layer solenoids have the same length and the same number of turns
but are placed co-axially one with in the other. The diameter of the inner coil is
8cm and that of the outer coil is 10cm. Calculate the co-efficient of coupling. [16]
3. (a) Derive an expression for the current, impedance, average power for a series RL
circuit excited by a sinusoidally alternating voltage and also find the power
factor of the circuit. Draw the phasor diagram.
(b) When a certain inductive coil is supplied at 240V, 50Hz, the current is 6.45A.
When the frequency is changed to 40Hz at 240V, the current drawn is 7.48A.
Calculate the inductance and resistance of the coil.
[8+8]
4. (a) Three identical impedances of (3+j4)Ω are connected in delta. Find an equivalent star network such that the line current is the same when connected to
the same supply.
(b) Three impedances of (7+j4)Ω, (3+j2)Ω and (9+j2)Ω are connected between
neutral and the R, Y and B phases. The line voltage is 440V, Calculate.
i. The line currents and
ii. The current in the neutral wire.
iii. Find the power consumed in each phase and the total power drawn by
the circuit.
[4+12]
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Set No. 3
Code No: Z0222/R07
5. (a) Write the tie - set schedule for the network shown in figure 5a
Figure 5a
(b) Using mesh analysis, determine the voltage V which gives a voltage of 50V
across 10 Ω resistor shown in figure 5b.
[6+10]
Figure 5b
6. (a) Using Norton’s theorem, find the current through the load impedance ZL as
shown in figure 6a.
Figure 6a
(b) State and explain reciprocity theorem.
[10+6]
7. In the circuit shown in the figure 7, the switch is put in position - 1 for 1 m sec
and then thrown to position - 2. Find the transient current in both intervals. [16]
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Set No. 3
Code No: Z0222/R07
Figure 7
8. For the circuit shown in figure 8, find the h parameters and ABCD parameters.
Check for reciprocity.
[8+8]
Figure 8
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Set No. 4
Code No: Z0222/R07
I B.Tech Supplementary Examinations, December 2012
ELECTRICAL CIRCUITS ANALYSIS
( Common to Electrical & Electronics Engineering and Instrumentation &
Control Engineering)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆⋆⋆⋆⋆
1. (a) A 100V, 60W bulb is connected in series with a 100V, 100W bulb and the
combination is connected across 200V supply. Find the value of resistance
that should be connected across the first bulb, so that each bulb may get the
rated current at the rated voltage.
(b) Two batteries A and B are joined in parallel. A resistance of 5Ω is connected
in series with this combination. Battery A has an emf of 110V and an internal
resistance of 0.2Ω, and the corresponding values of battery B are 100V and
0.25Ω. The above circuit is connected to 200V mains. Determine the magnitude and direction of the current in each battery and the total current taken
from the supply.
[6+10]
2. (a) Derive an expression for the energy stored in an inductor and a capacitor.
(b) Obtain an expression for Co-efficient of coupling.
[10+6]
3. A sinusoidal current wave is given by i=50 sin100πt. Determine
(a) The greatest rate of change of current.
(b) Derive average and rms values.
(c) The time interval between a maximum value and the next zero value.
[16]
4. Three inductive coils, each having a resistance of 20 Ω and reactance of 15 Ω are
connected.
(a) In star
(b) In delta, across a 3-phase, 400V, 50Hz supply. Calculate in each case, the
readings on two wattmeters connected in the circuit to measure the power
input. Also determine the phase and line currents in each case.
[16]
5. (a) State properties of trees.
(b) State the properties of complete incidence matrix.
[6+10]
6. (a) Find the current through the branch A-B of the network shown in the figure
6a using Thevenins theorem.
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Set No. 4
Code No: Z0222/R07
Figure 6a
(b) State and explain compensation theorem.
[6+10]
7. In the circuit shown in figure 7, Eg = 2.5 Volts. What are the values of i(t) and
[16]
VL(t) at t = 4 seconds.
Figure 7
8. Find the Y - parameters for the bridged T-network as shown in figure 8.
Figure 8
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[16]