Friday, June 22, 2012

BEL Previous year paper/ Sample paper

The pattern of the technical paper of PE is fully objective type paper. paper consist of almost equal no of question from all of the technical subjects in which most of the question is one line answer. there is no need of the calculator to solve the problem.
The paper also have the negative marking. please read the instruction before attempting the paper because no exact data given in the notification for the negative marking.The paper is given below...

if you know the answer of question write in the comment box. if any question found incorrect please also notify me......

                                  SAMPLE PAPER-1

 1. A differential amplifier amplifies the ---------- between two input signals.
a) addition
b) subtraction
c) multiplication
2. The differential amplifier can amplify ac as well as dc signals
because it
employs ----------.
3. Noise of input signal in differential amplifier
a) increases
b) decreases
c) remains the soul
4. Cascaded differential amplifier requires level translator because of
a) impedance matching
b) isolating each stage
c) d.c.shift.
5. In case of constant current bias ,R1 is replaced by diodes D1 & D2 TO
a) increase the input impedance
b) improve thermal stability
c) increase gain
6. If CMRR is high ,the wide variation of input within the tolerable limits of the
equipment makes output
a) high
b) low
c) the same

7. A binary half adder
a). Adds two binary digits and produces their sum and carry
b). Adds half the sum to the carry
c). Adds two binary digits and carry from previous addition
d). Adds two binary digits at half the speed

8. An index register in a computer is for
a. Arithmetic and logic functions
b. Storage of results
c. Modifying the address
d. Counting the no of programmes

9. An example of volatile memory is
a. RAM      b. ROM    c. EPROM         d. Magnetic tape

10. Barrier voltage in a P-N junction is caused by
a. Thermally generated electrons and holes
b. Diffusion of majority carriers across the junction
c. Migration of minority carriers across the junction
d. Flow of drift current

11. The temperature coefficient of an intrinsic semiconductor is
a. Positive    b. Negative     c. Zero    d. Like metals

12. A silicon transistor has a leakage current 1cbo = 1 ma. If the temp. rises by 50o C the leakage current will be
a. 30 ma    b. 32ma     c. 50ma         d. no change

12. The noise figure of an ideal amplifier in decibel is
a. 0.5   b. 0     c. 1      d. 10

13. The rise time of an amplifier is 200 nsec. Its bandwidth is
a. 70MHz     b. 140MHz           c. 100MHz         d. 1.75Mhz

14. MOSFET operates in
a. Depletion mode only
b. Enhancement mode only
c. Depletion and enhancement mode
d. None of these of the above

15. A device which behaves like SCRs is
a. UJT     b. Triac      c. MOSFET     d. SRD

16. A plate modulated class C RF amplifier produces 100 KW of radiated power at 100 % modulation. The modulating audio amplifier supplies approximately

a. 25KW   b. 33KW     c. 50KW       d. 66KW

17. A 100 MHz FM carrier, modulated by a 5 KHz sine wave deviates by 50 KHz. If the frequency of the modulating sine wave is doubled, the deviation will
a. Double   b. Half         c. Quadruple         d. Have no change

18. Noise generated by a resistor is dependent on
a. Its Value
b. Its temperature
c. Both value and temp
d. None of these

19. A 32 channel 8 bit PCM system samples at 8 KHz rate. The overall bit rate in kilobits per second will be
a. 2048           b. 2000               c. 1920               d. 64

20. Rsistivity ofGermanium in ohms cm. is approx. equal to
a. 50                   b. 10-12                c. 50k        d. 10-6

21. The number of free electrons/cubic cm intrinsic Germanium at room temperature is approx. equal to
a. 1.5*1010    b. 2.5*1013           c. 1000            d. 5*106

22. The number of free electrons/cubic cm of intrinsic silicon at room temperature is approx. equal to
a. 1.5*1010       b. 2.5*1013               c. 10000              d. 5*106

23. The forbidden energy gap for silicon is
a. 1.1eV       b. 067eV           c. 0.97eV            d. 1.7eV

24. The forbidden energy gap for Germanium is
a. 1.1eV        b. 067eV              c. 0.97eV             d. 1.7eV

25. N type material is formed by the addition of the following (penta valent )atom in n to semiconductor material
a. Antimony
b. Arsenic
c. Phosphorous
d. Any of the above

26. P type material is formed by the addition of the following [Trivalent] atom tn to semiconductor material
a. Boron      b. Gallium        c. Indium          d. Any of the above

27. Impurity atoms that produces N type material by its addition in semiconductor is called
a. Donar     b. Acceptor            c. Conductor          d. Insulator

28. Impurity atoms that produces P type material by its addition in semiconductor is called
a. Donar    b. Acceptor         c. Conductor         d. Insulator

29. Dynamic resistance of a diode Rd is if voltage changes is DVd and the current change is D Id
a. D Vd / D Id
b. D Id / D Vd
c. 1 / DVd
d. 1 / D Id

30. Point contact diodes are preferred at very high frequency, because of its low junction
a. Capacitance and inductance
b. Inductance
c. Capacitance

31. Identify the circuit given below
a. AND gate
b. OR gate
c. Rectifier
d. NOR gate

32. Identify the circuit given below
a. AND gate
b. OR gate
c. Rectifier
d. NOR gate

33. DC value of a Half wave rectifier with Em as the peak value of the input is
a. 0.318Em
b. 0.418Em
c. 0.518Em
d. 0.618Em

34. Change in Zener voltage of 10V at 100o C if temperature co-efficient is 0.072%o C as
a. 0.54 V        b. 0.74 V          c. 0.64 V              d. 0.14 V

35. If Tc is th e% temperature co of / oC and Vz as zener voltage and T as change in temperature then the change in zener voltage isb.
a. 100. Vz. Tc DT\
d. None of these of the above

36. VSWR on a transmission line is always
a. Equal to 1
b. Equal to 0
c. Less than 1
d. Greater than 1

37. In a amplitude modulated wave, the value of Vmax is 10V and Vmin is 5V. The % modulation in this case is:
a. 2%          b. 33.3%             c. 50%           d. 100%

38. The signal to noise ratio at the input of an amplifier can be improved:
a. By decrease the source impedance or resistance
b. By increasing the source impedance
c. By matching the source impedance with the input impedance of the amplifier
d. None of these

39. If the bandwidth of an amplifier is reduced, the thermal noise in the amplifier will:
a. Increase
b. Decrease
c. Not to be affected at all
d. Become random in nature

40. For the distortion to be minimum in a transmission line at audio frequencies, the condition is
a. L = CR / G
b. L = GR / C
c. LG = R
d. LR = G

41. When electromagnetic waves are propagated in a waveguide
a. They travel along the broader walls of the waveguide
b. They travel through the dielectric without touching the wall
c. They are reflected from the walls but they do not travel along them
d. None of these

42. Communication between satellite and ground station is through
a. Tropospheric scatter
b. Ground wave
c. Sky wave
d. Line of sight propagation

43. A mast antenna is used mainly for
a. UHF
b. Short wave
c. Medium wave
d. VHF

44. A crystal which has a sensitivity of -55 dBm with 1 MHz BW amplifier will have a sensitivity at 4 MHz BW amplifier equal to:
a. -55 dBm       b. -58 dBm            c. -52 dBm          d. -60 dBm

45. Electromagnetic waves are refracted when they
a. Pass into a medium of different dielectric constant
b. Are polarized at right angles to the direction of propagation
c. Encounter a perfectly conducting surface
d. Pass through a small slot in a conducting medium

46. An aerial is fed from an amplitude modulation amplifier. Both the modulating voltage and modulated voltage are sinusoidal. The aerial current (rms) before modulation is 5 A and it increases to 5.8A after modulation. The percentage of modulation index will be
a. 88% b. 80% c. 81.21% d. 83.14%

47. In a frequency demodulation, Foster-Seeley discriminator uses a
a. Single tuned circuit
b. Double tuned circuit in which both the primary and secondary are tuned to the same frequency
c. Double tuned circuit in which both the primary and secondary are tuned to to different frequencies
d. Combination of two transistors in push-pull operation

48. The wavelength of an electromagnetic wave in wave guide
a. Is directly proportional to the phase velocity
b. Is inversely proportional to the phase velocity
c. Is greater than that in free space
d. Depends only on the wave guide dimensions and the free space wavelength

49. The scale used for moving coil meter is
a. Non-linear scale
b. Linear scale
c. A square scale
d. A log scale

50. To double the circuit range of a 50 mA, 2000W meter movement, the shunt resistance requires is
a. 40W b. 50W c. 2000W d. 25KW

51. A voltmeter utilizes a 20 mA meter movement. The sensitivity of the voltmeter is
a. 50 meg ohms per volt
b. 20 K ohms per volt
c. 50 kilo ohms per volt
d. 20 meg ohms per volt

52. A transformer, with a 20 : 1 voltage step-down ratio has 6V across 0.6 ohm in the secondary, then Is and Ip given by
a. 10A, 5A
b. 5A, 10A
c. 10A, 0.5A
d. 1A, 0.5A

53. The temperature coefficient of resistance of a resistor is
a. Negative
b. Positive
c. Zero
d. Infinit

54 Two sequences x1 (n) and x2 (n) are related by x2 (n) = x1 (- n). In the z- domain, their
ROC’s are
(A) the same.
 (B) reciprocal of each other.
(C) negative of each other.
 (D) complements of each other

55. The Fourier transform of the exponential signal jt e 0 is
(A) a constant. 
(B) a rectangular gate.
(C) an impulse.
(D) a series of impulses.

56. The auto-correlation function of a rectangular pulse of duration T is
(A) a rectangular pulse of duration T.
(B) a rectangular pulse of duration 2T.
(C) a triangular pulse of duration T.
(D) a triangular pulse of duration 2T.

57. The FT of a rectangular pulse existing between t = − T / 2 to t = T / 2 is a
(A) sinc squared function. 
(B) sinc function.
(C) sine squared function. 
(D) sine function.

58.The system characterized by the equation y(t ) = ax(t )+ b is
(A) linear for any value of b. 
(B) linear if b > 0.
(C) linear if b < 0. 
(D) non-linear.

59.If G(f) represents the Fourier Transform of a signal g (t) which is real and odd
symmetric in time, then G (f) is
(A) complex. 
(B) imaginary.
(C) real. 
(D) real and non-negative.

60.A band pass signal extends from 1 KHz to 2 KHz. The minimum sampling frequency
needed to retain all information in the sampled signal is
(A) 1 KHz. 
(B) 2 KHz.
(C) 3 KHz. 
(D) 4 KHz

If you know the answer PLEASE give the answer in the Comments......




  1. This is great advice! Very honest and practical.I really enjoyed this post.Nice post!! these tips may help Great post, Jo! My favorite work advice.Thanks so much for a detailed post! It is very helpful for.Your post is helpful to avoid the mistakes. HR Interview Questions with Answers,Job Interview Questions and Answers