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BSNL GE-JTO Recruitment Examination -III

Paper : BSNL GE-JTO Recruitment Examination -III

NOTE : All Answer Are In BOLD Style.

1. For a parallel plate capacitor which is being charged out of the following the incorrect statement is
a) Energy stored in the capacitor does not enter it through the connecting wire through the space around the wires and plates of capacitor.
b) Rate at which energy flows into this volume is equal to the integration of the pointing vector over the boundary of the volume between the plates.
c) The pointing vector points everywhere radially outward of the volume between plates.
d) The pointing vector points everywhere radially into the volume between the plates.

2. The presence of alkali oxides in alumino silicate ceramics is likely to result in dielectric breakdown due to
a) Polarization
b) Conductivity
c) Structural homogeneties
d) Ionization

3. Which of the following will serve as a donor impurity in silicon
a) Boron     b) Indium    c) Germanium   d) Antimony

4. Electrical contact materials used in switches, brushes and relays must possess
a) High thermal conductivity and high melting point
b) Low thermal conductivity and low melting point
c) High thermal conductivity and low melting point
d) Low thermal conductivity and high melting point

5. The Maximum spectral response of the germanium and silicon is in the
a) infrared region   b) ultraviolet region c) visible region  d) x-ray region

6. For an insulating material, dielectric strength and dielectric loss should be respectively
a) high and high   b) low and high   c) high and low d) low and low

7. In a distortion factor meter, the filter at the front end is used to suppress
a) odd harmonics   b) even harmonics   c) fundamental component d) dc component

8. The coefficient of coupling between two air core coils depends on
a) mutual inductance between two coils only
b) self inductances of the two coils only
c) mutual inductance and self inductances of the two coils
d) none

9. Modern capacitors which have high capacitance in small size use a dielectric of
a) paper   b) rubber    c) ceramic d) Mylar

10. In any atom the potential energy of an orbiting electron is
a) always positive
b) always negative
c) sometime positive, sometime negative
d) numerically less than its kinetic energy

11. A  DE  MOSFET differs from a JFET in the sense that it has no ?
a) channel     b) gate     c) P-N junctions d) substrate

12. The advantage of a semiconductor strain gauge over the normal strain gauge is that
a) it is more sensitive
b) it is more linear
c) it is less temperature dependent
d) it's cost is low

13. Barrier potential 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

14. When an NPN transistor is properly biased then most of the electrons from the emitter
a) recombine with holes in the base
b) recombine in the emitter itself
c) pass through the base to the collector
d) are stopped by the junction barrier

15. The value of r when a transistor is biased to cut off is ?
a) 0.5     b) 0      c) 1.0 d) 0.8

16. A UJT can
a) be triggered by any one of it's three terminals
b) not be triggered
c) be triggered by two of its three terminal only
d) be triggered by all of its terminals only

17. An SCR can only be turned off via it's
a) cathode    b) anode c) gates   d) none

18. Gold is often diffused into silicon DN junction devices to
a) increase the recombination rate
b) reduce the recombination rate
c) make silicon a direct gap semiconductor
d) make silicon semi-metal

19. With n nodes and b branches a network will have
a) (b + n) links    b) b ? n + 1 links c) b ? n ? 1 links   d) b + n + 1 links

20. When a network has 10 nodes and 17 branches in all then the number of node pair voltages would be
a) 7       b) 9      c) 10       d) 45

21. A two port network having a 6 dB loss will give
a) an output power which is one ? quarter of the input power
b) an output power which is one ? half of the input power
c) an output voltage which is 0.707 of the input voltage
d) an output power which is 0.707 of the input power

22. While transporting a sensitive galvanometer ?
a) the terminals are kept shorted
b) critical damping resistance is connected across the terminals
c) the terminals are kept open circuited
d) it does not matter as to what is connected across the terminals

23. A T type attenuator is designed for an attenuation of 40 dB and terminating resistance of 75 ohms. Which of the following values represent full series and R1 and shunt arm R2 ?
1. R1 = 147W                          2. R1 = 153W
3. R2 = 1.5W                           4. R2 = 3750W
a) 1 and 3 b) 1 and 4     c) 2 and 3      d) 2 and 4

24. For a transmission line, the characteristic impedance with inductance 0.294mH/m and capacitance 60pF/m is
a) 49w     b) 60w        c) 70w d) 140w

25. When the graph of a network has six branches with three tree branches then the minimum number of equations required for the solution of the network is
a) 2          b) 3 c) 4      d) 5

26. Consider the following statement for a 2-port network
1. Z11 = Z22            2. h12 = h21
3. Y12 = -Y21           4. BC ? AD = -1
then the network is reciprocal if and only if
a) 1 and 2 are correct
b) 2 and 3 are correct
c) 3 and 4 are correct
d) 4 alone is correct

27. As a network contains only independent current sources and resistors then if the values of all resistors are doubled then the values of the node voltages are
a) will become half
b) will remain high
c) will become double
d) cannot be determined unless the circuit configuration and the values of the resistors are known

28. The energy of electric field due to a spherical charge distribution of radius r and uniform charge density d in vacuum is-
Ans. 5.4x109xQ2/r where Q=4/3(pie)r3d

29. Maxwell?s divergence equation for the magnetic field is given by
Ans. y

30. When a short grounded vertical antenna has a length L which is 0.05 l at frequency f and if it?s radiation resistances at f is R Ohms, then it?s radiation resistance at a frequency 2f will be
a) R/2 ohms       b) R ohms     c) 2R ohms    d) 4R ohms

31. In a cylindrical cavity resonator, the two modes which are degenerate would include
a) TE111 and TM111
b) TE011 and TM011
c) TE022 and TM111
d) TE111 and TM011

32. When an antenna of input resistance 73 ohm is connected to a 50-ohm line and if the losses are ignored then it?s efficiency will be nearly
a) 0.19     b) 0.81 c) 0.97    d) 1.19

33. If an isolated conducting sphere in air has radius = 1/ 4pqe0 it capacitance will be
a) Zero       b) IF c) 4pF     d) OF

34. When a dominant mode wave guide not terminated in it?s characteristic impedance is excited with a 10 GHz signal then if ?d? is the distance between two successive minima of the standing wave in the guide then
a) d = 1.5 cm
b) d is less then 1.5 cm
c) d is greater than 1.5 cm
d) d = 3cm

35. When a dipole antenna of l/8 length has an equivalent total loss resistance of 1.5 W then the efficiency of the antenna is
a) 0.89159 %    b) 8.9159 %    c) 89.159 % d) 891.59 %

36. In commercial FM broadcasting, the maximum frequency deviation is normally
a) 5 KHz        b) 15 KHz         c) 75 KHz d) 200 KHz

37. Weins bridge is used for measurement of frequency in the applied voltage waveform is measurement of frequency in the applied voltage waveform is
a) sinusoidal b) square      c) rectangular    d) triangular

38. Strain gauge is
a) not a transducer
b) an active transducer
c) not an electronic instrument
d) none

39. A high Q coil has
a) large band width    b) high losses    c) low losses d) flat response

40. In the case of an instrument reading of 8.3V with a 0 to 150 voltmeter having a guaranteed accuracy of 1% full scale reading, the percentage limiting error is
a) 1.810%         b) 0.181%        c) 18.10% d) 0.0018%

41. The 'h' parameter equivalent circuit of a junction transistor is valid for
a) High frequency, large signal operation
b) High frequency, small signal operation
c) Low frequency, small signal operation
d) Low frequency, large signal operation

42. A system is causal if the output of any time depends only on ?
a) Values of input in the past and in the future
b) Values of input at that time and in the past
c) Values of input at that time and in the future
d) None

43. A iron cored choke is a
a) Linear and active device
b) Non linear and passive device
c) Active device only
d) Linear device only

44. Poynting vector wattmeter uses
a) Seebeck effect     b) Ferranti effect   c) Induction effect d) Hall effect

45. Which one of the following is not a transducer in the true sense ?
a) Thermocouple     b) Piezoelectric pick ? up
c) Photo voltaic cell     d) LCD

46. The term used to denote a static device that converts ac to dc, dc to ac, dc to dc or ac to ac is
a) Converter system b) Inverter   c) Chopper   d) Thyristor

47. It is an unidirectional device that blocks the current flow from cathode to anode
a) SCR b) PCR      c) VCR       d) DCR

48. An ideal constant current source is connected in series with an ideal constant voltage source. Considering together the combination will be a
a) constant voltage source
b) constant current source
c) constant voltage and a constant current source or a constant power source
d) resistance

49. Anode current in an thyristor is made up of
a) electrons only   b) electrons or holes    c) electrons and holes d) holes only

50. For a pulse transformer, the material used for its core and the possible turn ratio from primary to secondary are respectively
a) ferrite : 20 : 1
b) laminated iron : 1 : 1
c) ferrite : 1 : 1
d) powdered iron : 1 : 1

51. A converter which can operate in both 3 pulse and 6 pulse modes is a
a) 1 phase full converter
b) 3 phase half wave converter
c) 3 phase semi converter
d) 3 phase full converter

52. A single phase CSI has capacitor C as the load. For a constant source current, the voltage across the capacitor is
a) square wave    b) triangular wave c) step function   d) pulsed wave

53. A single phase full wave midpoint thyristor converter uses a 230/200V transformer with centre tap on the secondary side. The P.I.V per thyristor is
a) 100V       b) 141.4V      c) 200V      d) 282.8V

54. In dc choppers for chopping period T, the output voltage can be controlled by FM by varying
a) T keeping Ton constant
b) Ton keeping T constant
c) Toff keeping T constant
d) None of the above

55. From the hot metal surface electrons escape because
a) of change of state from metal to gas due to heat.
b) of change of stats from gas to metal.
c) the energy supplied is greater than the work function
d) the energy is greater than Fermi level.

56. The most common device used for detection in radio receivers is ?
a) amplifier     b) triode       c) diode d) transistor

57. In a full wave rectifier the negative point in a circuit is
a) Either cathode
b) Either anode
c) The central tap on the high voltage secondary
d) Either plate

58. Negative feedback amplifier has a signal corrupted by noise as its input. The amplifier will
a) Amplify the noise as much as the signal
b) Reduce the noise
c) Increase the noise
d) Not effect the noise


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