### BSNL PAPER

BSNL JTO Exam 2005

1. At a frequency below the resonant frequency series circuit is

a) Inductive b) Capacitive c) Resistive d) None

2. The electrical conductivity of metals is typically of the order of (Ohm^-1 m^-1)

a) 10^7 b) 10^5 c) 10^-4 d) 10^-6

3. The output of a piezoelectric crystal has

a) Low amplitude and low impedance

b) High amplitude and high impedance

c) Low amplitude and high impedance

d) High amplitude and low impedance

4. The time constant associated with the capacitor charging in the circuit shown in the given figure is

a) 6ms b) 10ms c) 15ms d) 25ms

5. The Q factor of an inductor would be higher if it is made of

a) Thinner wire b) Longer wire c) Shorter wire d) Thicker wire

6. A cavity resonator can be represented by

a) An LC circuit b) An LCR circuit c) A lossy inductor d) A lossy capacitor

7. Air gap in the iron core of an inductor prevents

a) Core saturation b) Hysterisis loss c) Flux leakage d) Transformer action

8. Between the plates of an air capacitor if a glass slab is slipped without moving the plate then

a) Its capacitance is decreased b) Its capacitance is increased

c) Its capacitance is hardly affected d) Capacitor is discharged

9. For current to flow, a circuit must be

a) Isolated b) Insulated c) Complete d) Protected

10. Human ear can detect sound intensities of the order of

a) 10^-20 w/m2 b) 10^-13 w/m2 c) 10^-6 w/m2 d) 10^-3 w/m2

11. A FET operates on

a) Majority carriers only b) Minority carriers only

c) Positively charged ions only d) None

12. An SCR can conduct for a full half cycle or any part of it

a) and continue conduction for other half cycle

b) but blocks the conduction for other half cycle

c) nothing can be said

d) none

13. In CRT aquadag carries

a) aqueous solution of graphite

b) sweep voltage

c) secondary emission electrons

d) none of the above

14. From the following circuit, in order to obtain a 12-v stabilized supply the input to the terminals A and B should be

a) less than 12v with terminal A positive with respect to terminal B

b) greater than 12v with B positive with respect to A

c) less than 12v with A negative with respect to B

d) greater than 12v with A positive with respect to B

15. When the value of ICBO in a silicon transistor of b = 49 is 20 Na then the value of ICEO for a temperature rise of 180c would be

a) 8mA b) 160 hA c) 1mA d) 7.84mA

16. MOSFET can operate in

a) Depletion mode

b) Enhancement mode

c) Depletion-only mode

d) Both a & b

17. For a circuit design the very factor of an SCR, which is to be taken into account is

a) dx/dt rating b) dv/dt rating c) df/dt rating d) None

18. The functions of an oxide layer in an IC device is to

a) mask against diffusion or ion implant

b) insulate the surface electrically

c) produce a chemically stable protective layer

d) all the above

19. One of the following bipolar transistors which has the highest current gain bandwidth product for similar geometry is

a) NPN germanium transistor b) NPN silicon transistor

c) PNP germanium transistor d) PNP silicon transistor.

20. With the increasing temperature, the electrical conductivity would

a) Increase in metals as well as in intrinsic semiconductors.

b) Increase in metals but decrease in intrinsic semiconductors.

c) Decrease in metals but increase in intrinsic semiconductors.

d) Decrease in metals as well as in intrinsic semiconductors.

21. For the following circuit, the current X is 3A then the power delivered by the dependent current source D is

a) 50 watts b) 50 watts c) 1500 watts d) 15000 watts

22. The current in resistor R shown in the fig. will be

a) 0.2A b) 0.4A c) 0.6A d) 0.8A

23. In the network shown in the given fig. the capacitor C1 is initially charged to a voltage V0 before the switch S in the circuit is closed. In the steady state

a) C1 and C2 are charged to equal voltages

b) C1 and C2 are charged with equal coulombs

c) C1 and C2 are discharged fully

d) C2 alone is charged to voltage V0

24. The equivalent circuit of a wire-wound resistor can be represented as

Ans. d

25. For the fig. shown the fundamental cutset for the branch 12 is

a) 2, 1, 5

b) 2, 6, 7, 8

c) 2, 1, 3, 4, 5

d) 2, 3, 4

26. Ideally, attenuator pads should not change

a) voltage level b) impedance level

c) power level d) voltage, power or impedance level

27. When the two networks are cascaded through an ideal Buffer and if tr1 and tr2 are the rise times of the two networks, then the overall delay of the two networks together will be

a) sqrt(td1+td2) b) sqrt(td1^2+td2^2) c) td1+td2 d) (td1+td2)/2

28. For the network shown in the following fig. one of the following theorems which can be conveniently used to calculate the power consumed by the 10W resistor is

a) Thevenin's theorem

b) Maximum power transfer theorem

c) Millman's theorem

d) Superposition theorem

29. The nodal analysis is primarily based on the application of

a) KVL b) KCL c) Ohm's law d) Both b and c

30. When the driving point impedance of a network at a frequency of 1Hz is then the impedance can be realised as

31. For a lossless line

1. Series resistance is zero 2. Shunt conductance is zero

3. Shunt conductance is infinite 4. Series resistance is infinite

a) 1 & 2 b) 2 & 3 c) 2 & 4 d) 3 & 4

32. When a square wave is fed to an RC circuit then-

a) Voltage across R is square and across C is not square

b) Voltage across C is not square and across R is not square

c) Voltage across both R and C are square

d) Voltage across both R and C are not square

33. When an A.M. broadcast radio transmitter radiates 10 kw power when the modulation percentage is 60 then the power of the carrier is

a) 5.00 kw b) 7.69 kw c) 8.47 kw d) 9.17 kw

34. The main components of atmosphere responsible for absorption of em waves are

a) Nitrogen and Oxygen b) Nitrogen and hydrogen

c) Oxygen and water vapour d) Nitrogen and water vapour

35. The effective height of a linear antenna of length 'l' is say 'x' when the current distribution along it's length is uniform and say, it is 'y' when the current distribution is sinusoidal then x/y is equal to

a) 2 b) 1 c) 4/ p d) p/4

36. In a hollow rectangular waveguide, the phase velocity

a) Increases with increasing frequency

b) Decreases with increasing frequency

c) Is independent of frequency

d) Will vary with frequency depending upon the frequency range

37. For TM waves in a parallel plate waveguide, the minimum attenuation arising from imperfect conductors would occur at a frequency of (fc is the cut–off frequency)

a) 3fc b) Sqrt(3)fc c) 2fc d) Sqrt(2)fc

38. When a transmission line having 50 impedance is terminated in a load of (40 + j30) W then the VSWR is

a) j 0.033 b) 0.8+j0.6 c) 1 d) 2

39. The ionosphere plays a significant role in radio wave propogation at

a) High frequencies b) Ultra-high frequencies

c) Microwave frequencies d) Optical frequencies

40. When a carrier wave is modulated at 100% it's power is increased by

a) 100% b) 150 % c) 50% d) 0%

41. Reluctances in series are

a) Subtractive b) Additive c) Multiplicative d) None.

42. When the meters X and Y requires 40 mA and 50 mA respectively for full scale deflection then

a) X is more sensitive b) Y is more sensitive

c) both are equally sensitive

d) not possible to determine from the given data.

43. In the context of ac bridge measurement the term "Wagner Ground" means

a) a special RC connection that eliminates stray magnetic effects

b) any unwanted and unintended ground connection.

c) a large metal plate buried in the ground and connected to one corner of the bridge.

d) a special RC connection that eliminates stray capacitance effects.

44. The gating and counting circuits of a digital counter

a) cannot handle MHz signals

b) cannot handle GHz signals

c) can handle GHz signals

d) none.

45. De- sauty bridge is more widely used because of

a) simplicity

b) perfect balance for imperfect capacitors

c) perfect balance for air capacitors

d) maximum sensitivity.

46. A schottky diode clamp is used along with a switching BJT for

a) reducing the power dissipation.

b) reducing the switching time

c) increasing the value of b

d) reducing the base current.

47. The phenomenon of creeping occurs in

a) Energy meters

b) Ammeters

c) Wattmeter

d) Voltmeters

48. A permanent magnet moving coil measures the

a) true rms value b) dc value

c) peak value d) rms plus dc value

49. The D`Arsonval meter movement can be converted into an audio frequency ac ammeter by adding to it a

a) thermocouple b) rectifier c) chopper d) transducer

50. Which one of the following detectors is generally used in ac bridges for audio frequency range ?

a) Ac voltmeter b) CRO c) Headphones d) Vibration galvanometer.

51. In single phase circuit capacitor used for power factor correction decreases

a) The power factor b) The line current

c) Both a and b d) The line current and increases power factor

52. In the given figure X the balanced bridge should be

a) A self-inductance having resistance

b) A capacitance

c) A non-Inductive resistance

d) An inductance and a capacitance in parallel

53. SiO2 layer in an integrated circuit provides

a) Electrical connection to external circuit

b) Physical strength c) Isolation d) Conducting path

54. For an SCR with turn on time of 5 microsecond, an ideal trigger pulse should have

a) short rise time with pulse width = 3 m sec

b) vlong rise time with pulse width = 6 m sec

c) short rise time with pulse width = 6 m sec

d) long rise time with pulse width = 3 m sec

55. In a 3-phase half wave diode rectifier, the ratio of average output voltage to per phase maximum a c voltage is

a) 0.955 b) 0.827 c) 1.654 d) 1.169

56. In multiple pulse modulation used in PWN inverters, the amplitude and frequency for triangular carrier and square reference signals are respectively 4V, 6 KH2 and 1V, 1KH2. The number of pulses per half cycle and pulse width is respectively

a) 6, 90deg b) 3, 45deg c) 4, 60deg d) 3, 40deg

57. A four quadrant operation requires

a) two full converters in series.

b) two full converters connected back to back.

c) two full converters connected in parallel.

d) two semi converters connected back to back

58. In voltage source inverters

a) load voltage waveform Vo depends on load impedance z, where as load current waveform Io does not depend on z,

b) Both Vo and Io depend on z,

c) Vo does not depend on z where as Io depends on z

d) both Vo and Io do not depend on z

59. For an RC driving – point impedance function, the poles and zeros

a) should alternate on real axis

b) should alternate only on the negative real axis

c) should alternate on the imaginary axis

d) can lie anywhere on the left half place.

60. The functions of connecting a resistor in series with gate - cathode circuit and a zener diode across gate cathode circuit are, respectively to protect the gate circuit from

a) over voltages, over currents. b) over currents over voltages.

c) over currents, noise signals d) noise signals, over voltages.

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