CIVILS MAINS 2013 ELECTRICAL ENGINEERING (PAPER-I)

Time Allowed Three Hours Maximum Marks 250

QUESTION PAPER SPECIFIC INSTRUCTIONS

(Please read each of the following instructions carefully before attempting questions)

There are EIGHT questions divided in two Sections and printed both in HINDI and in ENGLISH.
Candidate has to attempt FIVE questions in all.
Question Nos. 1 and 5 are compulsory and out of the remammg, THREE are to be attempted choosing at least ONE question from each Section.
The number of marks carried by a question/part is indicated against it.
Answers must be written in the medium authorized in the Admission Certificate which must be stated clearly on the cover of this Question-cum-Answer Booklet in the space provided. No marks will be given for answers written in medium other than the authorized one.
Assume suitable data, if considered necessary, and indicate the same clearly.
Unless otherwise mentioned, symbols and notations have their usual standard meanings.
Attempts of questions shall be counted in chronological order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer Booklet must be clearly struck off.

SECTION-A

Using deltaY substitution, determine the resistance between a and in Fig. 1. 10
<img src='./qimages/100-1a.jpg'>

Figure 2 shows a square wave that is described through the range from 0 to 1t by and through the range from 1t to 21t by O. Find its Fourier components in the exponential series. 10
<img src='./qimages/100-1b.jpg'>

A conductor is charged by repeated contacts with a metal plate which, after each contact, is recharged to a quantity of charge Q by connecting it to a constant voltage source. If q is the charge of the conductor after the first operation, show that the ultimate charge on the conductor is

Design an ampliller with a gain of using one OP-AMP. Choose Ri 10 kil. 10

Write the Maxwell's equations including the continuity equation in vector form for time-varying fields in general medium naming each of them. 5
Define the following parameters for an OP-AMP Input offset voltage; Bias current; Slew rate; Output impedance; CMRR.5

Consider the unbalanced Wheatstone bridge shown in Fig. 3
<img src='./qimages/100-2a.jpg'>
The internal resistance of the galvanometer is 1 ohm. Using Thevenin's theorem, determine the galvanometer current. 20

Determine the current I in Fig. 4 using the ladder method. 20
<img src='./qimages/100-2b.jpg'>

In Fig. capacitor c1 is initially charged at 100 V and the other two capacitors are initially uncharged. The switch S is closed at time O. Find the current flowing through the resistor as a function of time.
<img src='./qimages/100-2c.jpg'> 10

3. Plane monochromatic waves are propagated parallel to the z-axis in both positive and negative directions. At the origin, the field strengths are given by
Ex= Acos(wt ± kz)
H x 0
Ey=O
Hy=Bcos(wt±kz)
Calculate the mean intensity of the radiation in each of the two directions in terms of B and the constants of the medium. 20

Show that the energy stored in a plane electromagnetic wave is equally divided between the electric and magnetic fields. 20

A lossless transmission line with air dielectric is 12 m long. What is the line length in wavelengths and what is the value of the phase constant beta at 15 MHz? 10

Using an OP-AMP, design a lossy integrator whose peak gain is 20 dB and the gain is 3 dB down from its peak when 10000 rad/sec. Use a capacitance of 0·01 uf 20

Design a voltage regulator using 7805 Ie to get a voltage output of 8 V. 10

Design a second-order low-pass Butterworth filter having a cutoff frequency of 1 kHz. Choose C O· 1 uF. The damping factor a is given to be 1'414. Choose Ri as 10kom

SECTION-B

Specify power supply voltage range, output logic 1 level voltage and output logic 0 level voltage for standard TTL gates. 10

Why are 'high power to size ratio machines' like mixer, hand drill, vacuum cleaner, etc., using DC universal motor? 10

Specify the type of core used in DC-DC converter and explain why iron core is not used in it. 10

How is good selectivity achieved in a superheterodyne receiver?

Draw a block diagram to implement logic F A .B using a 4 x 1 multiplexer. 10

6. Determine the MSP form of the switching function F(uvwxyz) sigma(O, II, 14-17, 20-22,30,32,33,36,37,48,49,52,53,59,63)using 6-variable Karnaugh map. 20

A sequential machine produces an output of I only when exactly two are followed by a 1 or exactly two are followed by a O. Determine the reduced state table of the machine. 20

Assuming that logic 0 is available, show that the INCLUSION gate is a universal building block. 10

7. A single-phase transformer of turns ratio 1 is connected to 110 V AC mains. It draws a primary current of 1 A at unity p.f. when delivering power to a load with an efficiency of 85%. If the no-load current of the transformer is 0·43 determine the p.f. at no load. 20

Draw the circuit diagram of SCR-based control circuit for full-range speed control of a shunt DC motor using two SCRs to run from single-phase AC mains. 20

What is the effect of gate capacitance of MOSFET in driving circuit when it is used in high-frequency power switching applications like sine wave inverter or DC-DC converter? 10

A certain FM signal is represented by V(tJ 10sin(10B t 15sin2000t) volts, where t is in seconds. Find the parameters of the FM wave. 20

Show that the Wiener-Hopf mter is practical only when the input SNR is small. 20

Explain why signal to noise ratio is better in FM receiver as compared to AM. Draw suitable diagrams in support of your explanation. 10