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B.E / B.Tech ( Part Time ) DEGREE ARREAR EXAMINATIONS, APRIL / MAY 2014
ELECTRICAL AND ELECTRONICS ENGINEERING
First Semester
PTEE131/PTEE181/PTEE9151-Electric Circuit Analysis
(Regulations 2002/2005/2009)
Time: 3 Hours
Answer ALL Questions
Max. Marks 100
PART-A (10 x 2 = 20 Marks)
1.
State Kirchoff's laws.
2.
Define form factor for sinusoidal waveform.
3.
Calculate the time constant of RC circuit having R= 1 kft and C =1 p.F.
4.
Define poles and zeros of network function.
5.
Draw the power triangle for X >Xc-
6.
Determine the resonant frequency of circuit L=0.5 mH and C=10|iF.
7.
List down the rules for constructing nodal admittance matrix.
8.
Define Compensation theorem.
9.
Calculate the mutual inductance if L =L =10mH and K=0.5.
10.
Two wattmeter method is used to measure power, the two wattmeter reads is 5 KW
and -1 KW respectively. Calculate the power factor of the circuit.
L
1
2
Part - B ( 5 x 16 = 80 marks)
11.
(i) Calculate the equivalent resistance across B & C using Star delta transformation in
Fig-1
(8)
Fig.1
(ii) Find the average value, r.m.s value, form factor and peak factor of a periodic wave
having the following values for equal time intervals changing suddenly from one value
to next: 0, 5, 10,20,50,60,50,20,10,5,0,-5,-10 Vetc. What would be the r.m.s value of a
sine wave having the same peak value?
(8)
12.
a)
Find the expression for the current in a series RLC circuit fed by a d.c. voltage of
20 V with R= 4 Q, L=1 H and C= % F. Assume initial conditions to be zero.
(OR)
13.
b)
A series circuit has R=10 Q and L=0.1 H connected with 50 Hz sinusoidal voltage
of maximum value of 400 V is applied across the circuit. Find an expression for the
value of current at any instant after the voltage is applied, assuming that the
voltage is zero at the instant of application. Calculate its value 0.02 second after
switching on.
a)
Two impedance Z^= 5 - j13.1Q and Z = 8.57 + j6.42Q are connected in parallel
across a voltage of (100+j200) volts. Calculate 1) Branch currents 2) Total power
consumed.
(OR)
(i) A series circuit consisting of 25 Q resistor, 64 mH inductor and 80nF capacitor is
connected to a 110V.50 Hz single phase supply. Calculate the current, voltage
across individual element and overall PF of the circuit and also draw the phasor
diagram.
(8)
b)
2
(ii) A series RLC circuit consists of a 1kQ resistor and an inductance of 100 mH in
series with 10pF.lf 100 V, 50 Hz ac supply is applied as input. Determine 1)
resonant frequency 2) Maximum current 3) Quality factor.
(8)
14.
a)
(i) Determine the current I using Mesh analysis shown in Fig. 2a.
(ii) Find the current through 5Q in Fig, 2b. using Norton's theorem.
(6)
(10)
10 f!
5t)
-VWv-
01!
-VMr-
0.2 O
0.1 Q
4V
5tl
Fig. 2a.
b)
Fig. 2b.
(OR)
(i) Find V in Fig.2c. using Nodal analysis.
(ii) Verify Reciprocity theorem in the network shown in Fig.2d
n
(8)
(8)
WW
0.4 V,
Fig. 2c.
15.
a)
b)
Fig. 2d
(i) If a coil of 800 p.H is magnetically coupled to another coil of 200 JAH. The
coupling coefficient is 0.05. Calculate inductance if two coils are connected in (i)
Series aiding (ii) Series opposing (iii) Parallel aiding (iv) Parallel opposing.
(8)
(ii) Three inductive coils each having resistance of 16£2 and reactance of 12Q are
connected in star across a 400 V, three phase 50 Hz. Calculate (i) Line & Phase
Voltages (ii) Line & Phase Currents (iii) power factor (iv) Phasor diagram.
(8)
(OR)
Prove that a three phase balanced load draws three times as much power when
connected in delta, as it would draw when connected in star.