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UGC NET JUN 2007 : ELECTRONIC SCIENCE PAPER III

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Signature and Name of Invigilator Roll No. (In figures as per admission card) 1. (Signature) (Name) Roll No. 2. (Signature) (Name) Test Booklet No. J 8 8 0 7 Time : 2 hours] (In words) PAPER III ELECTRONIC SCIENCE Number of Pages in this Booklet : 32 [Maximum Marks : 200 Number of Questions in this Booklet : 26 Instructions for the Candidates U U 1. Write your roll number in the space provided on the top of this page. 1. U DU U S U U U U U 2. U U U, U S U U 2. Answers to short answer/essay type questions are to be given in the space provided below each question or after the questions in the Test Booklet itself. U U No Additional Sheets are to be used. 3. U U U, - S U U U - S U U 3. At the commencement of examination, the question booklet will be given to you. In the first 5 minutes, you are requested to open the booklet and compulsorily examine it as below : (i) - S U U U U U U U S U U- U S S U U (i) To have access to the Test Booklet, tear off the paper seal on the edge of this cover page. Do not accept a booklet without sticker-seal and do not accept an open booklet. (ii) U DU U U U - S DU U U U U U U S DU / U U U U U S S U U U U U S U U - S U U - S U UQ (ii) Tally the number of pages and number of questions in the booklet with the information printed on the cover page. Faulty booklets due to pages/questions missing or duplicate or not in serial order or any other discrepancy should be got replaced immediately by a correct booklet from the invigilator within the period of 5 minutes. Afterwards, neither the question booklet will be replaced nor any extra time will be given. 4. U U 4. Read instructions given inside carefully. 5. One page is attached for Rough Work at the end of the booklet before the Evaluation Sheet. 5. U U- S (Rough Work) U U DU 6. If you write your name or put any mark on any part of the Answer Sheet, except for the space allotted for the relevant entries, which may disclose your identity, you will render yourself liable to disqualification. 6. U- S U , U U U U 7. U # U U- S U U U U U # U U U U 7. You have to return the Test booklet to the invigilators at the end of the examination compulsorily and must not carry it with you outside the Examination Hall. 8. / U Z U S U 8. Use only Blue/Black Ball point pen. 9. Use of any calculator or log table etc. is prohibited. 9. U ( U U) U U 10. There is NO negative marking. 10. U U J 8807 1 P.T.O. ELECTRONIC SCIENCE PAPER III NOTE : J 8807 This paper is of two hundred (200) marks containing four (4) sections. Candidates are required to attempt the questions contained in these sections according to the detailed instructions given therein. 2 SECTION - I Note : This section contains five (5) questions based on the following paragraph. Each question should be answered in about thirty (30) words and each question carries five (5) marks. (5x5=25 marks) The broad definition of a transducer includes devices which convert mechanical energy into electrical energy. These devices form a very large and important group of transducers commonly used in industrial instrumentation. Many physical parameters such as heat, intensity of light, sound, vibration, acceleration, pressure, magnetic field, liquid level, noise, force, etc., may be converted into electrical signal by means of the electrical transducers. These transducers provide an output signal in the form of electrical signal when stimulation by a mechanical or a non-mechanical input, for example, a photoconductor converts light intensity into change of resistance, a thermocouple converts heat energy into electrical voltage, a force produces a change in resistance in a strain gauge, an acceleration produce a voltage in a piezoelectric crystal and so on. In all cases, however, the electrical output is measured by standard methods; giving the magnitude of the input quantity in terms of an analogous output. 1. Differentiate between the active and passive transducers. J 8807 3 P.T.O. 2. Explain the working principle of a thermocouple. 3. Describe the Hall effect and its application in transducers. J 8807 4 4. State the piezoelectric effect and explain how it is utilized in transducers for the measurement of force. 5. Explain the operating principle of a photovoltaic cell. J 8807 5 P.T.O. SECTION - II Note : This section contains fifteen (15) questions each to be answered in about thirty (30) words. Each question carries five (5) marks. (5x15=75 marks) 6. Draw the hybrid equivalent circuit of a BJT in CE configuration and explain the physical meaning of different h - parameters used in the circuit J 8807 6 7. State and prove Thevenin s theorem. 8. Compare capacitive and inductive transducers with regard to their utility. J 8807 7 P.T.O. 9. Draw a Schmitt trigger circuit and explain its working. 10. Define the reverse recovery time and reverse recovery current of the power diodes. J 8807 8 11. Give the method for the fabrication of npn monolithic transistors. 12. Define slew-rate in an operational amplifier. How off-set is adjusted in an operational amplifier ? J 8807 9 P.T.O. 13. Draw an equivalent circuit of a TRIAC and a circuit diagram using TRIAC for controlling AC power. 14. Prove the following are the Exclusive OR function. (a) (A1B) (A1B) , (b) AB1A B J 8807 10 15. Explain the vectored interrupt and device polling. 16. Define quantization noise. Which type of modulation employs quantization and explain how ? J 8807 11 P.T.O. 17. Describe the need and method of use of pointers in C. 18. Compare the characteristics of n-channel and p-channel JFETs. J 8807 12 19. Define gain and radiation efficiency of an antenna. Write the properties of an isotropic antenna. 20. With the help of a schematic diagram, describe the working principle of a two - cavity klystron. J 8807 13 P.T.O. SECTION - III Note : 21. This section contains five (5) questions of twelve (12) marks each. Each question is to be answered in about two hundred (200) words. (12x5=60 marks) Draw an equivalent circuit of a lossy transmission line and find the expressions for the characteristic impedance, attenuation constant and phase propagation constant. Discuss the difference between characteristic impedance and line impedance. 22. The input signal in the Figure-1 shown above is a square wave of 50Hz alternating between 612V. (a) (b) Find the output vo , waveform shape and amplitude. Calculate the minimum slew-rate. 23. Explain how a JK flip flop can be converted into a T - flip flop. 24. Write the control words for the following configuration of the parts of Intel 8255 for mode 2 operations. Part A mode of 25. bidirectional Part A - mode 2 Part B mode of - output Part B - mode 1 Explain and derive an expression for the followings with respect to the FM modulator (a) Modulation index (b) The voltage distribution in FM wave (c) The power in modulated FM wave J 8807 14 J 8807 15 P.T.O. J 8807 16 J 8807 17 P.T.O. J 8807 18 J 8807 19 P.T.O. J 8807 20 J 8807 21 P.T.O. J 8807 22 J 8807 23 P.T.O. SECTION - IV Note : This section consists of one essay type question of forty (40) marks to be answered in about one thousand (1000) words on any of the following topics. (40x1=40 marks) 26. (a) Explain the operation of the pn-junction diode in the forward and reverse bias conditions. Discuss the effect of doping in the semiconductor. (b) Find the recification efficiency and ripple factor of a bridge rectifier. (c) Draw a shunt - voltage regulator circuit and explain its functioning. (d) Draw a successive approximation type A/D converter circuit and explain its functioning. OR (a) Draw a circuit to control the speed of a DC series motor using SCR and explain its functioning. (b) Describe the GUNN effect and explain the operation of GUNN device under quenched mode. (c) Draw a Wein-bridge oscillator circuit and find its oscillation condition. (d) Draw a frequency modulator and demodulator circuits and explain its operation. J 8807 24 J 8807 25 P.T.O. J 8807 26 J 8807 27 P.T.O. J 8807 28 J 8807 29 P.T.O. J 8807 30 J 8807 31 P.T.O. FOR OFFICE USE ONLY 1 26 51 76 2 27 52 77 3 28 53 78 4 29 54 79 5 30 55 80 6 31 56 81 7 32 57 82 8 33 58 83 9 34 59 84 10 35 60 85 11 36 61 86 12 37 62 87 13 38 63 88 14 39 64 89 15 40 65 90 16 41 66 91 17 42 67 92 18 43 68 93 19 44 69 94 20 45 70 95 21 46 71 96 22 47 72 97 23 48 73 98 24 49 74 99 25 50 75 Marks Obtained Question Number Marks Obtained Question Number Marks Obtained Question Number Marks Obtained Question Number Marks Obtained 100 Total Marks Obtained (in words) ..................................... (in figures) .................................... Signature & Name of the Coordinator ............................... (Evaluation) J 8807 Date ............................. 32

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Additional Info : Ugc Net June 2007 Question Paper - Electronic Science Paper III
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