BEL PE Electronics Papers 2008

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Bharat Electronics Limited (BEL) is going to conduct the Probationary Engineer Exam For Electronics and Communication Engineering Students in 2015. BEL PE Electronics Papers 2008 Questions is given below. BEL PE previous papers for electronics and communication will give an idea about the questions pattern and the subject which are important for the exam. In PE Electronics 150 number of questions shall be asked consisting of Technical questions related to Electronics Discipline  and 30 Questions from the General Aptitude questions.

BEL PE Electronics Papers 2008

1. A memory system of size 16 k bytes is to be designed using memory chips which have 12 address lines and 4 data lines each. The number of such chips required to design the memory system is

  • A.2
  • B. 4
  • C.8
  • D. 18

Answer: C

2. In a 7 segment display, LEDs b and c lit up. The decimal number displayed is

  • A.9
  • B. 7
  • C.3
  • D. 1

Answer:  D

3. The number of LED display indicators in logic probe are

  • A. 1
  • B. 2
  • C. 1 or 2
  • D. 4

Answer:  B

4. The time needed by a TTL circuit to switch from 0 to 1 or 1 to 0 is about

  • A. 10 μs
  • B. 10 ns
  • C. 100 μs
  • D. 50 ns

Answer: B

5. The hexadecimal number 64 AC is equivalent to decimal number

  • A.25727
  • B. 25722
  • C.25772
  • D. 25777

Answer: C

6. Noise limiter is provided on AM receivers to

  • A. reduce interfering noise due to ignition system
  • B. reduce noise due to electrical storms
  • C. reduce interference due to electrical machinery
  • D. all of the above

Answer: D

7. A low ratio of the A.C. load impedance of a diode detector results in

  • A. diagonal clipping
  • B. poor AGC operation
  • C. poor AF response
  • D. negative peak clipping

Answer:  D

8.  The conduction loss verses device current  characteristics of power MOSFET in best approximately by

  • A. a parabola.
  • B. an exponentially decaying function.
  • C. a rectangular hyperbola.
  • D. a straight line.

Answer: A. a parabola.

9. Poles & zeroes are at .01,1,20,100.Find phase margin/angle at f=50Hz.
Answer : 90 (By drawing bode plot)

10. Phase velocity of waves propagating in a hollow metal waveguide is

  • A. greater than the group velocity
  • B. less than the velocity of light in free space
  • C. equal to the velocity of light in free space
  • D. equal to group velocity

Answer: Option A

11. Gain of an directional antenna 6db P=1mw find transmitted power ? ( Hints : Ptr= G * P.)

12. Multiplication of two nos 10101010 & 10010011 in 2’s complement form..

13. A circuit is supplied with 15v with a series of resistance of 1k and a parallel combination of 12V zener diode and 2k resistance. Find current through 2k resistance.
Answer: 6mA

14. A MP has 16 line data bus & 12 line adder bus find memory range ?
Answer:  4K(4*1024bytes)

15. Divide by 12 counter require minimum _____no of flip flops
Answer:  4

16. Storage time in p-n junction.

17.  Succesive approx. used in_____
Answer: ADCm(analog to digital)

18. Pre-emphasis require in _____low freq/high freq signal.

19. Handshake in MP ____
Answer:  to communicate with slower peripherals.

20. Binary equivalent of 0.0625
Answer: 0.0001

21. The letter EPROM Stands for ______
Answer: Erasable PROM

22. Currently most popular form of external bulk storage for micro computer is
Answer:  Floppy Disk

23.When we add 6 in BCD operations_____
Answer: if result exceed valid BCD nos.

24. Shottky diode has better switching capability because it switch between_____

25. Figure of Merit is same as____

26. Switching in diode happens when____

27. During forward bias majority charge conc. in depletion layers inc/decreases____

28. Channel capacity depend on_____
Answer:   Usable frequency or bandwidth

29.A 2kHz signal is passed through an Low pass filter having cut-off freq 800Hz o/p will be

30. Carrier amplitude 1v, peak to peak message signal 3mv find modulation index.

31.A 12V signal is quantized into two V/14 & 6 equal V/7 determine equalization error.

32. Fourier Transform of a symmetric conjugate function is always real

Answer:  True

33.Divide by 12 counter requires a minimum of 4 flip flops?

Answer:  True

34. Boron can be use as impurity to analyse base of a npn transistor ?

Answer: True

35.  How many 4-bit words can be stored in a 512 bit ROM ?

Answer:  128

36. At room temperature the current in an intrinsic semiconductor is due to

  • A. holes
  • B. electrons
  • C. ions
  • D. holes and electrons

Answer:  D
37. Work function is the maximum energy required by the fastest electron at 0 K to escape from

the metal surface.

  • A. True
  • B. False

Answer:  B
38. The most commonly used semiconductor material is

  • A. silicon
  • B. germanium
  • C. mixture of silicon and germanium
  • D. none of the above

Answer:  A

39. In which of these is reverse recovery time nearly zero?

  • A. Zener diode
  • B. Tunnel diode
  • C. Schottky diode
  • D. PIN diode

Answer:  C

40. A transistor has a current gain of 0.99 in the CB mode. Its current gain in the CC mode is

  • A. 100
  • B. 99
  • C. 1.01
  • D. 0.99

Answer:  A

6. In an n channel JFET, the gate is

  • A. n type
  • B. p type
  • C. either n or p
  • D. partially n & partially p

Answer:  B


41. The amount of photoelectric emission current depends on

  • A. frequency of incident radiation
  • B. intensity of incident radiation
  • C. both frequency and intensity of incident radiation
  • D. none of the above

Answer:  B

42. At very high temperatures the extrinsic semi conductors become intrinsic because

  • A. drive in diffusion of dopants and carriers
  • B. band to band transition dominants over impurity ionization
  • C. impurity ionization dominants over band to band transition
  • D. band to band transition is balanced by impurity ionization

Answer:  B

 

43. Ferrite have

  • A. low copper loss
  • B. low eddy current loss
  • C. low resistivity
  • D. higher specific gravity compared to iron

Answer:  C

44. A cycloconverter can be

  • A. step down
  • B. step up
  • C. step down or step up
  • D. none of the above

Answer:  C

45. In a 3 phase fully controlled converter the firing frequency is

  • A. 3 times the line frequency
  • B. 6 times the line frequency
  • C. 9 times the line frequency
  • D. 12 times the line frequency

Answer:  B

46. Two thyristor of same rating and same specifications

  • A. will have equal turn on and turn off periods
  • B. will have equal turn on but unequal turn off periods
  • C. may have equal or unequal turn on and turn off periods
  • D. will have unequal turn on and turn off periods

Answer:  C

47. A semiconverter feeding an RLE load operates in

  • A. first quadrant only
  • B. first and second quadrants
  • C. first and fourth quadrants
  • D. first and third quadrants

Answer:  A

48. The phenomenon of overlap in converter operation due to

  • A. source resistance
  • B. source inductance
  • C. both source resistance and source inductance
  • D. high value of firing angle

Answer:  B

49. In a single phase full wave converter (M – 2 connection) feeding a highly inductive load, the firing angle for each thyristor is a in the respective half cycle. The period of conduction of each thyristor is

  • A. p – a
  • B. p
  • C. p + a
  • D. p – 2a

Answer:  B

50. An SCR is triggered at 40° in the positive half cycle only. The average anode current is 50 A. If the firing angle is changed to 80°, the average anode current is likely to be

  • A. 50 A
  • B. 25 A
  • C. less than 50 A but more than 25 A
  • D. less than 25 A

Answer:  C

51. Thyristors are suitable for dc circuit breakers but not for ac circuit breakers.

  • A. True
  • B. False

Answer:  B
52. The value of capacitor C for dynamic equalizing circuit of series connected thyristors is

determined by

  • A. forward characteristics of thyristors
  • B. reverse recovery characteristics of thyristors
  • C. both forward and reverse recovery characteristics of thyristors
  • D. none of the above

Answer:  B

53. A chopper

  • A. converts constant voltage dc into ac and then into variable voltage dc
  • B. converts constant voltage dc into variable voltage dc directly
  • C. converts ac of one frequency into ac of another frequency
  • D. converts ac to dc

Answer:  B

54. In a single phase full wave regulator, the firing angles in the positive and negative half cyclesare generally

  • A. equal
  • B. different
  • C. equal or different
  • D. different but sometimes equal

Answer:  A

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