Assignment 4

Course: B. Tech. Branch: A5 Year and Semester: 2008 / Ist Semester Subject Code and Name: Basic Electrical & Electronics Engg. (EE-101) Subject Teacher: Neeraj Sharma Submission Date: 8th Dec 2008 Topics covered: Electrical transducer, Piezo-resistive strain gauge, P – N semiconductor, rectifier, transistors, SCR, FET, LCD, opto-coupler, Zener diode, LED. Section A (Short answer type questions) 1. 2. 3. 4. 5. 6. 7. 8. 9.

What is electrical transducer? Why is natural quartz considered most suitable material for piezoelectric transducer? Why are strain gauge called the piezo-resistive stain gauge? What are P & N type semi-conductors? What is cut in voltage in semi-conductor? What is the effect of reverse bias on width of P-N junction? What is PIV of a diode in a rectifier circuit? Why is input impedance of the FET is very high? Why is FET is called uni-polar transistor? 10. What is meant by break-over voltage of an SCR? Define latch current of an SCR? 11. What are the factors on which turn off time of an SCR depend? 12. What is an opto-coupler? 13. What are advantages of LCD over LED? 14. List important features of LCD. 15. What is an LED? What are its various drawbacks? Section B (Numerical problems/ subjective questions) 1. A linear resistance potentiometer is 50mm long and is uniformly wound with a wire of total resistance 5,000 ohms. Under normal condition, the slider is at center of potentiometer. Determine the linear displacement when resistance of pot, as measured by wheatstone bridge is 1850 ohms. If it is possible to measure a minimum value of 5 ohms resistance with above arrangement. Determine the resolution of pot in mm? 2. The output of LVDT is connected to a 5V voltmeter through an amplifier whose amplification factor is 250.An output of 2mV appears across the terminals of LVDT when the core moves through a distance of 0.5mm.Calculate the sensitivity of LVDT and that of the whole set up. The milli-voltmeter scale has 100 divisions. The scale can be read to 1/5 of a division. Calculate the resolution of the instrument in mm. 3. Explain the construction and working of a strain gauge. Describe various use of this gauge. 4. Describe the operation of an LVDT? Describe the performance characteristic of an LVDT? 5. What is Hall effect? Why is it more pronounced in semi-conductor than in metal? Describe working principle, construction and application of Hall effect transducer? 6. Describe the working principle and construction of the thermocouple? 7. Explain the zener and avalanche thermal breakdown mechanism. What will be their thermal co-efficient? 8. Draw a simple FET amplifier circuit and explain its working? 9. Explain the basic construction of SCR. Explain its principle of operation using two-transistor model. Explain turn off mechanism of SCR? 10. Draw NPN and PNP transistor. Label all current and show direction of flow. 11. Sketch V-I characteristic for different gate current of SCR and indicate holding current, latching current and break over voltage. 12. What is difference between light sensitive devices and light generating opto-electric devices? Give their examples. Enumerate few application of opto-electronic devices 13. What is LED? Give its principle of working, construction, circuit symbol, merit, demerit and applications?

Section C (Objective/ fill in the blanks type questions) 1. 2. 3. 4. 5. 6. 7. 8. 9.

LED stand for______________________ FET has very high input______ Three elements used as N type impurities are________,_______,_______. Two mechanism of breakdown in P-N junction are _________,__________. Gas filled phototubes have _________________ characteristics. Capacitive transducer has very high________________. LVDT has________ characteristics. LVDT can be used frequency upto____________ Thermocouple can be made from____________,__________________.