# BSNL GE-JTO Paper on 7 June 2013

Discussion in 'Latest Placement papers' started by krishna, Aug 19, 2013.

1. ### krishnaBanned

BSNL GE-JTO Recruitment Examination

Test Paper - IV

Reactive current through the inductive load produces-

a) Magnetic field

b) Electric field

c) Super magnetic field

d) None

When a piece of copper and another of germanium are cooled from room temperature to 800 K then the resistance of -

a) each of them increases

b) each of them decreases

c) copper increases and germanium decreases

d) copper decreases and germanium increases

A capacitance transducer has two plates of area 5 cm2 each separated by an air gap of 2mm. Displacement sensitivity in pF /cm due to gap change would be -

a) 11.1

b) 44.2

c) 52.3

d) 66.3

The critical angle in degrees, for an electromagnetic wave passing from Quartz (m = m0, Î=4Îo) into air is-

a) 15

b)30

c)45

d)90

When an RC driving point impedance function has zeros at s= -2 and s=-5 then the admissible poles for the function would be –

a) s = 0; s = -6

b) s = -1; s = -3

c) s = 0; s = -1

d) s = -3; s = -4

A capacitor used for power factor correction in single- phase circuit decreases –

a) the power factor

b) the line current

c) Both the line current and the power factor

d) the line current and increases power factor

The unit of inductance is –

a) ohm

b) inductive reactance

c) inducta

d) Henry

Which type of by-pass capacitor works best at high frequencies –

a) electrolytic

b) mica

c) ceramic

d) plexiglass

The usual value of the surge impedance of a telephone line is –

a) 600 W

b) 500 W

c) 75 W

d) none

Telemetering is a method of –

a) counting pulses, sent over long distances

b) transmitting pictures from one place to another

c) transmitting information concerning a process over a distance

d) None

In an unbiased P-N junction thickness of depletion layer is of the order of –

a) 0.005 mm

b) 0.5 mm

c) 5 mm

d) 10-10 m

One of the semiconductor device, which behaves like two SCRs is–

a) UJT

b) triac

c) JFET

d) MOSFET

The following, which is not an advantage of semiconductor strain gauges as compared to conventional strain gauges, is –

a) excellent hysterists characteristics

b) least sensitive to temperature changes

c) high fatigue life

d) smaller size

The fundamental ripple frequency of a half wave 3F rectifier with a 3F supply of frequency 50 Hz is –

a) 150 Hz

b) 50 Hz

c) 100 Hz

d) 250 Hz.

For an FR biased PNP transistor –

a) base is negative with respect to emitter

b) collector is positive with respect to emitter

c) collector is a little more positive than base

d) base is a little less positive with respect to emitter than collector

With normal operation of a JFET one can get IDss –

a) the maximum drain current

b) the minimum drain current

c) normal drain current

d) none

An SCR is a semiconductor device made up of –

a) Four N type layers

b) Two P types and three N type layers

c) Two P type and two N type layers

d) Three P type and one N type layers

For a UJT, if R1 = resistance from emitter to base 1, R2 = resistance from emitter to the base 2 and RBB = R1 + R2 then the intrinsic stand off ratio (h) is –

a)

b)

c)

d)

As the drain voltage is increased for a junction FET in the pinch off region then the drain current –

a) becomes zero

b) abruptly decreases

c) abruptly increases

d) remains constant

20 When the energy gap of a semiconductor is 1.1eV then it would be –

a) opaque to the visible light

b) transparent to the visible light

c) transparent to the infrared radiation

d) opaque to the infrared radiation

The equivalent capacitance across ab will be –

d.0

In the following fig. the power dissipated is maximum when the value of Rx is –

a) 33.4 K

b) 17.6 K

c) 10 K

d) 5 K

The transfer function of a low pass RC network is –

The total capacitance across points 'a' and 'b' in the given figure is –

a) 1.66 mF

b) 2.66 mF

c) 3.5 mF

d) 4.5 mF

The load resistance needed to extract maximum power from the following circuit is –

a) 2W

b) 9W

c) 6W

d) 18W

Which one of the following conditions for z parameters would hold for a two port network containing linear bilateral passive circuit elements –

a) z11 = z22

b) z12z21 = z11z22

c) z11z12 = z22z21

d) z12 = z21

In the network shown, the switch is opened at t = 0. Prior to that, the network was in the steady state, Vs(t) at t = 0 is –

a) 0

b) 5V

c) 10V

d) 15V

Which of the following statements are correct –

1. Tellegen's theorem is applicable to any lumped network

2. The reciprocity theorem is applicable to linear bilateral networks.

3. Thevenin's theorem is applicable to two terminal linear active networks.

4. Norton's theorem is applicable to two terminal linear active networks.

a) 1, 2 and 3

b) 1, 2, 3 and 4

c) 1, 2 and 4

d) 3 and 4

Which one of the following transfer functions represents the critically damped system ?

When the respective coil impedance of the circuit shown in the fig. is are Z1 = (5 + j8)W and Z2=(3+j8) then the input impedance of the circuit will be –

a) (8 + 16j)W

b) (2 + j0)W

c) (15 + 64j)W

d) (8 + 0j)W

One of the following statement which is not correct -

a) In case of an antenna, the radiation resistance and loss resistance are not two different quantities.

b) The loss resistance includes loss by eddy currents, improper earth connections, insulation leakages etc) but not I2R losses

c) Radiation resistance varies directly as square root of the frequency

d) None of the above

Ultraviolet radiation emitted when electron jumps from an outer stationary orbit to -.

a) first stationary orbit

b) second stationary orbit

c) third stationary orbit

d) fourth stationary orbit

When the signal is propogated in a waveguide which has a full wave of electric intensity change between the two farther walls and no component of the electric field in the direction of propogation then the mode is –

a) TE11

b) TE10

c) TM22

d) TE20

Consider the following statements pertaining to parabolic antenna -

1.It is commonly used above 1GHz

2. It get’s circularly polarized

3. It’s radiation pattern is highly directional

4. It’s radiation pattern is cardiod

of these statements-

a) 1,2 and 4 are correct

b) 1 and 3 are correct

c) 1,2 and 3 are correct

d) 2 and 4 are correct

When a vertical dipole antenna is used in conjunction with a loop antenna for direction finding, then the field pattern obtained will be-

When one end of a loss less transmission line of length 3/8 l and characteristic impedance R0 is short circuited and the other end is terminated in Ro then the impedance at l/8 away from the end terminated in R0 is-

a) Zero

b) R0

c) R0/2

d) Infinite

For transmission of wave from a dielectric permittivity Î1 into dielectric medium of lower permittivity Î2 (Î1 > Î2) the critical angle of incidence Qc ( relative to the interface ) is given by -

A transmission line has primary constants R, L, G and C and secondary constants Z0 and g (= a + jb) if the line is loss less then .

The intrinsic impedance of a free space is-

One of the following which is a low gain but omni directional antenna is-

a) discone

b) log-periodic

c) loop

d) helical

Electronic voltmeters have –

a) high input impedance

b) low input impedance

c) zero input impedance

d) none

Which of the following statement about impulse voltage is true ?

a) An impulse voltage is an unidirectional voltage.

b) In chopped impulse voltage, flashover does not occur.

c) Time taken to rise is exactly equal to the time taken to fall.

d) RMS value of impulse voltage is always less than 50% of average value.

The precision of an instrument indicates its ability to reproduce a certain reading with a given –

a) drift

b) resolution

c) shift.

d) consistency

In heterodyne digital conductor, the input signal is heterodyned to a –

a) higher frequency

b) lower frequency

c) both a and b)

d) none

In a digital measuring device, if the input electrical signal is in the frequency range dc to fmax Hz, then it must be sampled at a rate of –

a) fmax times/sec

b) fmax times/ses

c) every 2fmax/sec

d) 2 fmax times/sec .

Moving Iron intruments measures the rms value of –

a) a direct quantity

b) an alternating quantity

c) a virtual quantity.

d) none.
2. ### krishnaBanned

One of the following intruments which is used almost exclusively to measure radio frequency current is-

a) Moving coil meter

b) Rectifier-type moving coil meter

c) Iron-vane meter

d) Thermocouple meter.

A good ohmic contact on a p- type semiconductor chip is formed by introducing –

a) gold as an impurity below the contact

b) a high concentration of donors below the contract

c) a high concentration of acceptors below the contact

d) a thin insulator layer between the metal and semiconductor.

The use of thermocouple meters for ac measurement leads to a meterscale which is –

a) linear

b) square law

c) logarithmic

d) exponential

If low pressure of the order of 10-6mm of Hg is to be measure then the instrument of choice would be-

a) compound pressure gauge

b) thermocouple vacuum gauge

c) pirani gauge

d) ionization type vacuum gauge

In the given circuit if the power dissipated in the 6W resister is zero then V is –

a)

The equivalent circuit of a resistor is shown in the given figure. The resistor will be non inductive if –

a)

b)

c)

d)

SCR turns OFF from conducting state to blocking state on –

a) reducing gate current

b) reversing gate voltage

c) reducing anode current below holding current value

d) applying ac to the gate

Static V-I characteristics of an SCR with different gate drives applied to the gate are indicated by-

a) I92 > I 91 > I 90

b) V92 > V91 > V90

c) P92 > P91 > P90

d) either a or b

Each diode of a 3 phase, 6-pulse bridge diode rectifier conducts for-

a) 60o

b) 1200

c) 1800

d) 900

A load, consisting of R = 10W and wL = 10W is being fed from 230 V, 50 Hz source through a 1 phase voltage controller. For a firing angle delay of 300 , the rms value of load current would be-

a) 23 A

The total number of SCRs conducting simultaneously in a 3 phase full converter with overlap considered has the sequence of-

a) 3,3, 22

b) 3, 3, 3, 2

c) 3, 2, 3, 2

d) 2, 2, 2, 3

A single phase voltage controller, using two SCRs in antiparallel is found to be operating as a controlled rectifier. This is because

a) load is R and pulse gating is used

b) load is R and high frquendy carrier gating is used

c) load is RL and pulse gating is used

d) load is RL and continuous gating is used

The inverse Fourier Transform of

In a GTO anode current begins to fall when gate current-

a) is negative peak at time t = 0

b) is negative peak at t = shortage period ts

c) just begins to become negative at t = 0

d) is negative peak at t = (ts + fall time)

Power amplifiers and Audio use

a) Ferrite core

b) Air core

c) Solid iron core

d) Laminated iron core

The amplifiers which are inserted at intervals amplify the signal and compensate for transmission less on the cable are called-

a) Line amplifiers

b) Equalizing amplifiers

c) Rep eaters

d) Compandors

A solid state device named TRIAC acts as a ----- switch

a) 3 terminal unidirectional

b) 2 terminal unidirectional

c) 3 terminal bi-directional

d) 2 terminal bi-directional

Identify the fastest logic circuit when speed of operation is concerned-

a) TTL

b) RTL

c) DTL

d) ATL

An amplifier CE is characterized by-

a) Low voltage gain

b) Moderate power gain

c) Very high output impedance

d) Signal phase reversal

The standard symbol for EX-OR gate is –

a) b)

c) d)

Boolean algebra is based on –

a) numbers

b) logic

c) truth

d) symbols

Magnetic amplifiers are used for –

a) voltage amplification

b) power amplification

c) current amplification

d) frequency amplification

Number of resistors required for an N bit D/A converter in R-2R ladder D/A converter is-

a) 4N

b) 1N

c) 3N

d) 2N

'Not allowed' condition in NAND gate SR flip flop is –

a) s = 0, R = 0

b) s = 1, R = 1

c) s = 0, R = 1

d) s = 1, R = 0

In a PID controlles the transfer function G(s) is

A time invariant linear stable system is forced with an input x(t) = A sin wt under steady state conditions, the output Y(t) of the system will be –

a) A sin (wt + f), where f = tan-1|G(jw) |

b) A G (jw) | A sin [wt + G(jw)]

c) | G (jw) | A sin [2 wt + G (jw)]

d) | G (jw) A sin [wt + G (jw)]

x(t)-------G(s)---------y(t)

Mark the wrong statement for two phase servo motor –

a) The rotor diameter is small

b) The rotor resistance is low

c) The applied voltages are seldom balanced

d) The torque speed characterstic are linear.

The gain phase plot of open loop transfer function of four different systems labelled A, B, C, and D

are shown in the figure. The correct sequence of the increasing order of stability of the four systems will be-

a) A, B, C, D

b) D, C, B, A

c) B, A, D, C,

d) B, C, D, A

A unity feedback system has G(S) = . In the loot locus, the break away point occurs between

a) S = 0 and –1

b) S = -1 and ¥

c) S = -1 and –2

d) S =-2 and – ¥

Twice in a year a few minute disturbance occurs in space communication during sun-blinding when --- are in line

a) Sun and satellite

b) Sun and earth station

c) Satellite and earth station

d) Sun, satellite and earth station

The traffic handling capacity of an Earth station on the up link depends on-

a) It’s EIRP

b) Satellite antenna gain

c) Noise associated with the satellite

d) All of the above

A supergroup pilot is –

a) applied at each multiplexing bay

b) used to regulate the gain of individual repeaters

c) applied at each adjustable equalizer

d) fed in at a GTE

If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of

a) Ö2

b) 2

c)
3. ### krishnaBanned

Date: may 12, 2013

1. An Aeroplane travels at 400 km/hr at sea level where the temperature is 15oC. The velocity of the Aeroplane at the same Mach number at an altitude where a temperature of -25Cis prevailing, would be
a) 126.78 km/hr
b) 130.6 km/hr
c) 371.2 km/hr
d) 400.10 km/hr (Ans)

2. The plot for the pressure ratio along the length of the convergent-divergent nozzle is shown in the given figure. The sequence of the flow conditions labelled 1,2,3, and 4 in the figure is respectively

a) supersonic, sonic, subsonic and supersonic
b) sonic, supersonic, subsonic and supersonic
c) subsonic, supersonic, sonic and subsonic
d) subsonic, sonic, supersonic and subsonic (Ans)

3. If the full -scale turbine is required to work under a head of 30 m and to run at 428 r.p.m., then a quarter-scale turbine model tested under a head of 10 m must run at
a) 143 r.p.m.
b) 341 r.p.m.
c) 428 r.p.m.
d) 988 r.p.m. (Ans)

4. The dimensionless group formed by wavelength λ, density of fluid ρ, acceleration due to gravity g and surface tension σ, is
a) σ (Ans)
λ2gρ
b) σ
λg2ρ
c) σg
λ2ρ
d) ρ
λ2gρ

5. Which one of the following sets of standard flows is uperimposed to represent the flow around a rotating cylinder ?
a) Doublet, vortex and uniform flow (Ans)
b) Source, vortex and uniform flow
c) Sink, vortex and uniform flow
d) Vortex and uniform flow

6.

A float of cubical shape has sides of 10 cm. The float valve just touches the valve seat to have a flow area of 0.5 cm2 as shown in the given figure. If the pressure of water in the pipeline is 1 bar, the rise of water level h in the tank to just stop the water flow will be
a) 7.5 cm
b) 5.0 cm (Ans)
c) 2.5 cm
d) 0.5 cm

7. A U-tube manometer is connected to a pipeline conveying water as shown in the given figure. The pressure head of water in the pipeline is

a) 7.12 m
b) 6.56 m
c) 6.0 m (Ans)
d) 5.12

8. The eye of a tornado has a radium of 40 m. If the maximum wind velocity is 50 m/s, the velocity at a distance of 80 m radius is
a) 100 m/s
b) 2500 m/s
c) 31.25 m/s
d) 25 m/s (Ans)

9. If a vessel containing liquid moves downward with constant acceleration δ, then
a) the pressure throughout the liquid mass is atmosphere
b) the pressure in the liquid mass is greater than the hydrostatic pressure
c) there will be vacuum in the liquid
d) the pressure throughout the liquid mass is greater than atmosphere (Ans)

10. Improve streamlining produces 25% reduction in the drag coefficient of a torpedo. When it is travelling fully submerged and assuming the driving power to remain the same, the increase in speed will be
a) 10 % (Ans)
b) 20 %
c) 25 %
d) 30 %

11. If a bullet is fired in standard air at 15oC at the Mach angle of 30oC, the velocity of the bullets would be
a) 513.5 m/s
b) 585.5 m/s
c) 645.5 m/s
d) 680.5 m/s (Ans)

12. A stream function is given by (x2-y2). The potential function of the flow will be
a) 2xy + f(x)
b) 2xy + constant (Ans)
c) 2(x2-y2)
d) 2xy + f(y)

13. The height of a cylindrical container is twice that of its diameter. The ratio of the horizontal forces on the wall of the cylinder when it is completely filled to that when it is half filled with the same liquid is
a) 2 (Ans)
b) 3
c) 3.5
d) 4

14. The velocities and corresponding flow areas of the branches labelled 1,2,3,4 and 5 for a pipe system shown in the given figure are given in the following table :
Pipe Label l Velocity Area
1 5 cm/s 4 sq cm
2 6 cm/s 5 sq cm
3 V3 cm/s 2 sq cm
4 4 cm/s 10 sq cm
5 V5 cm/s 8 sq cm

a) 2.5 cm/s
b) 5 cm/s (Ans)
c) 7.5 cm/s
d) 10 cm/s

15. A pipe is connected in series to another pipe diameter is twice and length is 32 times that of the first pipe. The ratio of frictional head losses for the first pipe to those for the second pipe is (both the pipes have the same frictional constant)
a) 8
b) 4
c) 2
d) 1 (Ans)

16. Which one of the following statements is correct ?
a) Hydraulic grade line and energy grade line are the same in fluid flow problems
b) Energy grade line lies above the hydraulic grade line and is always parallel to it
c) Energy grade line lies above the hydraulic grade line and they are separated from each other by a vertical distance equal to the velocity head (Ans)
d) The hydraulic grade line slopes upwards meeting the energy grade line only at the exit of flow

17. If laminar flow takes place in two pipes, having relative roughnesses of 0.002 and 0.003, at a Reynolds number of 1815, then
a) the pipe of relative roughness of 0.003 has a higher friction factor (Ans)
b) the pipe of relative roughness of 0.003 has a lower friction factor
c) both pipes have the same friction factor
d) no comparison is possible due to inadequate data

18. A pipeline connecting two reservoirs has its diameter reduced by 20% due to deposition of Chemicals. For a given head difference in the reservoirs with unaltered friction factor, this would cause a reduction in discharge of
a) 42.8% (Ans)
b) 20%
c) 17.8%
d) 10.6%

19. A tank containing water has two orifices of the same size at depths of 40 cm and 90 cm below the free surface of water. The ratio of discharges through these orifices is
a) 1:1
b) 2:3 (Ans)
c) 4:9
d) 16:81

20. A Pilot static tube is used to measure the velocity of water using a differential gauge which contains a manometric fluid of relative density 1.4. The deflection of the gauge fluid when water flows at a velocity of 1.2 m/s will be (the coefficient of the tube may be assumed to be 1)
a) 183.5 mm
b) 52.4 mm (Ans)
c) 5.24 mm
d) 73.4 mm

21. The development of boundary layer zones labelled P,Q, R and S over a flat plate is shown in the given figure

Based on this figure, match List (Boundary layer zones) with List II (Types of boundary layer) and select the correct answer using the codes given below the Lists :
List -I List -II
a) P 1. Transitional
b) Q 2. Laminar viscous sub-layer
c) R 3. Laminar
d) S 4. Turbulent
Codes :
A B C D
a) 3 1 2 4 (Ans)
b) 3 2 1 4
c) 4 2 1 3
d) 4 1 2 3

22. A pipe of 20 cm diameter and 30 km length transports oil from a tanker to the shore with a velocity of 0.318 m/s. The flow is laminar. If μ = 0.1 N-m/s2, the power required for the flow would be
a) 9.25 kW (Ans)
b) 8.36 kW
c) 7.63 kW
d) 10.13 kW

23. In a turbulent boundary layer over the entire length of a plate, the boundary layer thickness increases with its distance X from the leading edge as
a) X 1/2
b) X1/5
c) X2/5
d) X4/5 (Ans)

24. Separation of fluid flow is caused by
a) reduction of pressure in the direction of flow
b) reduction of the boundary layer thickness
d) presence of favourable pressure gradient

25. When pressure drag over a body is large as compared to the friction drag, then the shape of the body is that of
a) an aerofoil
b) a streamlined body
c) a two-dimensional body
d) a bluff body (Ans)

26. A circular cylinder of 400 mm diameter is rotated about its axis in a stream of water having a uniform velocity of 4 m/s. When both the stagnation points coincide, the lift force experienced by the cylinder is
a) 160 kN/m
b) 10.05 kN/m (Ans)
c) 80 kN/m
d) 40.2 kN/m

27. An automobile moving at a velocity of 40km/hr is experiencing a wind resistance of 2kN. If the automobile is moving at a velocity of 50km/hr, the power required to overcome the wind resistance is
a) 43.4kW (Ans)
b) 3.125 kW
c) 2.5 kW
d) 27.776 kW

28. When a cylinder is placed in an ideal fluid and the flow is uniform, the pressure coefficient Cp is equal to
a) 1-sin2θ (Ans)
b) 1- 2 sin2θ
c) 1- 4 sin2θ
d) 1- 8 sin2θ

29. If the upstream Mach number of a normal shock occuring in air (k=1.4) is 1.68, then the Mach number after the shock is
a) 0.84
b) 0.646 (Ans)
c) 0.336
d) 0.564

30. Which one of the following sets of thermodynamic laws/ relations is directly involved in determining the final properties during an adiabatic mixing process?
a) The first and second laws of thermodynamics
b) The second law of thermodynamics and steady flow relations
c) Perfect gas relationship and steady flow relations
d) The first law of thermodynamics and perfect gas relationship (Ans)

31. The air wiht enthalpy of 100 kJ/kg is compressed by an air compressor to a pressure and temperature at which its enthalpy becomes 200 kJ/kg. The loss of heat is 40kJ/kg from the compressor as the air passes through it. Neglecting kinetic and potential energies, the power required for an air mass flow of 0.5 kg/s is
a) 30kW (Ans)
b) 50kW
c) 70kW
d) 90kW
4. ### krishnaBanned

32. Consider the following statements :
i) The first law of thermodynamics is a law of conservation of energy
ii) Perpetual motion machine of the first kind converts energy into euivalent work
iii) A closed system does not exchange work or energy with its surroundings
iv) The second law of thermodynamic stipulates the law of conservation of energy and entropy. Which of the statements are correct ?
a) (i) and (iii)
b) (ii) and (iv)
c) (ii), (iii) and (iv)
d) (i), (ii) and (iii) (Ans)

33. A heat engine receives 1000 kW of heat at a constant temperature of 285 oC and rejects 492 kW of heat at 5oC. Consider the following thermodynamic cycles in this regard:
(i) Carnot cycle
(ii) Reversible cycle
(iii) Irreversible cycle
Which of these cycles could possible be executed by the engine ?
a) 1 alone (Ans)
b) 3 alone
c) 1 and 2
d) None 1, 2 and 3

34. The process 1-2 for steam shown in the given figure is

a) isobaric
b) isentropic
c) isenthalpic (Ans)
d) isothermal

35. In which one of the following working substances, does the relation T2 = (P2)0.286 hold good if the process takes place with zero heat transfer ?
T1 P1
a) West steam
b) Superheated steam (Ans)
c) Petrol vapour and air mixture
d) Air

36. Consider the following statements :
When dry saturated steam is throttled from a higher pressure to a lower pressure, the
a) pressure decreases and the volume increases (Ans)
b) temperature decreases and the steam becomes superheated
c) temperature and the dryness fraction increase
d) entropy increases without any change in enthalpy

37. In which one of the following situations the entropy change will be negative
a) Air expands istothermally from 6 bars to 3 bars (Ans)
b) Air is compressed to half the volume at constant pressure
c) Hear is supplied to air at constant volume till the pressure becomes three folds
d) air expands isentropically from 6 bars to 3 bars

38. The heat added to a closed system during a reversible process is given by Q = αT + βT2, where α and β are constants. The entropy change of the system as its temperature changes from T1 to T2 is equal to

39. The internal energy of a gas obeying van der Waals equation (p + a/V2) (v-b) = RT depends on its
a) temperature
b) temperature and pressure (Ans)
c) temperature and specific volume
d) pressure and specific volume

40. Consider the following statements :
A real gas obeys perfect gas law at very
(i) high temperature
(ii) high pressure
(iii) low pressures
Which of these statements is/are correct ?
a) (i) alone
b) (i) and (iii)
c) (ii) alone
d) (iii) alone (Ans)

41. The capacity of an air compressor is specified as 10 m3/min. It means that the compressor is capable of
a) supplying 3 m3 of compressed air per minute (Ans)
b) compressing 3 m3 of free air per minute
c) supplying 3 m3 of compressed air at NTP
d) compressing 3 m3 of standard air per minute

42. A two-stage compressor takes in air at 1.1 bars and discharges at 20 bars. For maximum efficiency, the intermediate pressure is
a) 10.55 bars
b) 7.33 bars
c) 5.5 bars
d) 4.7 bars (Ans)

43. For the same maximum pressure and heat input, the most efficient cycle is
a) Otto cycle (Ans)
b) Diesel cycle
c) Brayton cycle
d) Dual combustion cycle

44. In a petrol engine car, which one of the following performance characteristics is affected by the front-end volatility of the gasoline used ?
a) Hot starting and vapour lock
b) Engine warm -up and spark plug fouling
c) Spark plug fouling and hot starting
d) Vapour lock, engine warm -up and spark plug fouling (Ans)

45. In turbo prop, the expansion of gases takes place approximately
a) 100% in the turbine (Ans)
b) 80% in the turbine and 20% in the nozzle
c) 50% in the turbine and 50% in the nozzle
d) 100% in the nozzle

46. The most commonly used moderator in Nuclear power plants is
a) heavy water
b) concrete and bricks
c) steel
d) graphite (Ans)

47. Shielding in a nuclear reactor is generally done to protect against
a) excess electrons
b) X-rays
c) α and β rays
d) neutron and gamma rays (Ans)

48. Partial admission steam turbine refers to the situation where the
c) nozzles do not occupy the complete circumference leading into the annulus

49. In a steam power plant, the ratio of the isentropic heat drop in the prime mover to the amount of heat supplied per unit mass of steam is known as
a) stage efficiency
b) degree of reaction
c) Rankine efficiency (Ans)
d) relative efficiency

50. Reciprocating compressors are provided with
a) simple disc/plate valve (Ans)
b) poppet valve
d) solenoid valve

51. The gross head available to hydraulic power plant is 100m. The utilised head in the runner of the hydraulic turbine is 72 m. If the hydraulic efficiency of the turbine is 90% , the pipe friction head is estimated to be
a) 20 m (Ans)
b) 18 m
c) 16.2 m
d) 1.8 m

52. Which one of the following pairs of formulae represents the specific speeds of turbine and pump respectively ? (Notations have their usual meanings)
a) NQ 1/2 and NP1/2
H3/4 H5/4
b) NQ 1/2 and NP1/2
H3/4 H3/4
c) NP1/2 and NQ1/2
H3/4 H5/4
d) NP 1/2 and NQ1/2 (Ans)
H5/4 H3/4

53. The outer surface of a long cylinder is maintained at constant temperature. The cylinder does not have any heat source
The temperature in the cylinder will
c) be independent of radius (Ans)

54. A composite plane wall is made up of two different materials of the same thickness and having a thermal conductivities of k1 and k2 respectively. The equivalent thermal conductivity of the slab is
a) k1+k2

b) k1k2

c) k1+k2 (Ans)
k1k2

d) 2k1k2
k1+k2

55. A copper wire of radius 0.5 mm is insulated with a sheathing of thickness 1 mm having a thermal conductivity of 0.5 W/m-K. The outside convective heat transfer coefficient is 10W/m2-K. If the thickness of insulation sheathing is raised by 10 mm, then the electrical current-carrying capacity of the wire will
a) increase
b) decrease
c) remain the same (Ans)
d) vary depending upon the electrical conductivity of the wire

56. For the fully developed laminar flow and heat transfer in a uniformly heated long circular tube, if the flow velocity is doubled and the tube diameter is halved, the heat transfer coefficient will be
a) double of the original value
b) half of the original value (Ans)
c) same as before
d) four times of the original value

57. Heat transfer by radiation between two grey bodies of emissivity ε is proportional to (notations have their usual meanings)
a) (Eb - J)
(I - ε)
b) (Eb - J) (Ans)
(I - ε) /ε
c) (Eb - J)
(I - ε)2
d) (Eb - J)
(I - ε2)

58. The Nusselt number is related to Reynolds number in laminar and turbulent flows respectively as
a) Re-1/2 and Re0.8
b) Re1/2 and Re0.8 (Ans)
c) Re-1/2 and Re-0.8
d) Re1/2 and Re-0.8

59. In respect of free convection over a vertical flat plate the Nusselt number varies with Grashof number 'Gr' as
a) Gr and Gr1/2 for laminar and turbulent flows respectively (Ans)
b) Gr 1/2 and Gr1/3 for laminar and turbulent flows respectively
c) Gr1/4 and Gr1/3 for laminar and turbulent flows respectively
d) Gr1/3 and Gr1/4 for laminar and turbulent flows respectively

60. The enthalpies at the beginning of compression, at the end of compression and at the end of condensation are respectively 185 kJ/kg and 85 kJ/kg. The COP of the vapour compression refrigeration system is
a) 0.25
b) 5.4
c) 4 (Ans)
d) 1.35
5. ### krishnaBanned

61. The COP of a heat pump βHP and the COP of a refrigerator βRef are related as
a) βHP + βRef
b) βHP - βRef = 1 (Ans)
c) βRef - βHP = 1
d) βHP - βRef = 0

62. The discharge pressure of the compressor in the refrigeration system goes up due to the
a) lower volumetric efficiency of the compressor
b) formation of scale in the condenser (Ans)
c) large size of the condenser
d) undercharge of the refrigerant

63. The leakage in a Freon-based refrigeration system can be detected by using a/an
a) oxy-acetylene torch
b) halide torch (Ans)
c) sulphur torch
d) blue litmus paper

64. When warm saturated air is cooled
a) excess moisture condenses (Ans)
b) excess moisture condenses but relative humidity remains unchanged
c) excess moisture condenses and specific humidity increases but relative humidity remains unchanged.
d) specific humidity increases and relative humidity decreases

65. When dry-bulb and wet-bulb temperature are identical, it means that the
a) air is fully saturated and dew-point temperature has reached
b) air is fully saturated (Ans)
c) dew-point temperature has reached and humidity is 100%
d) partial pressure of water vapour is equal to total pressure

66. The desirable air velocity in the occupied zone for comfort for summer air-conditioners is in the range of
a) 6-7 m/minute
b) 4-5m/minute
c) 2-3 m/minute
d) 0.5-1.5 m/minute (Ans)

67. An air-conditioned room of volume 10 cm3 has infiltration of air equivalent to 3 air changes. Density of air is 1.2 kg/3, specific heat Cp is 1 kJ/kg-K and temperature difference between room and ambient air is 20K. The sensible heat load due to infiltrated air is
a) 60 kJ/hr
b) 12 kJ/hr
c) 6 kW
d) 0.2 k W (Ans)

68. If heat and mass transfer take place simultaneously, the ratio of heat transfer coefficient to the mass transfer coefficient is a function of the ratio of
a) Schmidt and Reynolds numbers (Ans)
b) Schmidit and Prandtl numbers
c) Nusselt and Lewis number
d) Reynolds and Lewis numbers

69. Consider the following statements :
The typical air velocities in the ducts of air-conditioning systems are
(i) lower in residential buildings as compared to those of public buildings
(ii) higher in residential buildings as compared to those of public buildings
(iii) higher in industrial buildings as compared to those of public buildings
(iv) equal in all types of buildings
Which of these statements is/are correct ?
a) (i) alone
b) (i) and (iii) (Ans)
c) (ii) and (iii)
d) (iv) alone

70. Consider the following parameters :
(i) Dry-bulb temperature
(ii) Humidity ratio
(iii) Air velocity
Which of these parameters are taken into account for determining effective temperature for human comfort ?
a) (i) and (ii)
b) (i) and (iv)
c) (ii), (iii) and (iv)
d) (i), (ii) and (iii) (Ans)
6. ### krishnaBanned

Date 22 April, 2013

BSNL electronics and electrical solved question papers

1. To neglect a voltage source, the terminals across the source are

(A) open circuited

(B) short circuited (Ans)

(C) replaced by some resistance

(D) replaced by an inductor

2. Current I0 in the given circuit will be

(A) 10 A

(B) 3.33 A (Ans)

(C) 20 A

(D) 2.5 A

Solution : RT = 2 + 2 || [1 + (2 || 2)]

= 2 + 2 || (1 + 1)

= 2 + 2 || 2 = 2 + 1 = 3 Ω

So I = 40 A
3

By current division I0 = 1 * 1 * 40 = 10 A
2 2 3 3

I0 = 3.33 A

3. In a resonant circuit, the power factor at resonance is

(A) zero

(B) unity (Ans)

(C) 0.5

(D) 1.5

4. In the given circuit voltage V is reduced to half. The current will become

(A) I/2 (Ans)

(B) 2 I

(C) 1.5 I

(D) I / √R2 + (XL + XC)2

Solution : I a V if V reduced half current becomes I .
2

5. The function 3 s has
(s + 1) (s + 2)

(A) one zero, two poles (Ans)

(B) no zero, one pole

(C) no zero, two poles

(D) one zero, no pole

Solution : G (s) = 3s has one zero at s = 0 and two poles at s = - 1, - 2.
(s + 1) (s + 2)

6. One electron volt is equivalent to

(A) 1.6 * 10-10 J

(B) 1.6 * 10-13 J

(C) 1.6 * 10-16 J

(D) 1.6 * 10-19 J (Ans)

7. Which of the following is donor impurity element ?

(A) Aluminium

(B) Boron

(C) Phosphorous (Ans)

(D) Indium.

8. The diameter of an atom is of the order

(A) 10-6 m

(B) 10-10 m (Ans)

(C) 10-15 m

(D) 10-21 m

9. The following Figure represents

Image - BSNL- MB (J.T.O.) RE 2001 - Part A - Qno. 9

(A) LED (Ans)

(B) Varistor

(C) SCR

(D) Diac

10. If the d.c. valve of a rectified output is 300 V and peak to peak ripple voltage is 10 V, the ripple factor is

(A) 1.18%

(B) 3.33% (Ans)

(C) 3.36%

(D) 6.66%

Solution : rms value of output

= √3002 + 102 = 300.166 V

Average value = 300 V

Form factor RMS value = 300.166 = 1.00055.
Average value 300

Ripple factor = √(Form factor)2 - 1

= √(1.0005)2 - 1 = 0.0333

= 3.33%.

11. Full wave rectifier output has ripple factor of

(A) 1.11 (Ans)

(B) 1.21

(C) 1.41

(D) 1.51

12. In a common base connection IE = 2 mA, IC = 1.9 mA. The value of base current is

(A) 0.1 m (Ans)

(B) 0.2 mA

(C) 0.3 mA

(D) zero

Solution : IE = 2 mA IC = 1.9 mA

Ib = IE - IC = (2 - 1.9) = 0.1 mA.

13. For the action of transistor the base region must be

(A) P-type material

(B) N-type material

(C) very narrow (Ans)

(D) highly doped

14. Compared to a CB amplifier the CE amplifier has higher

(A) current amplification

(B) output dynamic resistance

(C) leakage current

(D) input dynamic resistance

(E) all of the above (Ans)

15. When a transistor is biased to cut-off its Y is

(A) 0.5

(B) 0

(C) 1.0 (Ans)

(D) 0.8

16. An ideal voltage amplifier should have

(A) Ri = 0, R0 = 0

(B) Ri = 0, R0 = ¥

(C) Ri = ¥, R0 = 0 (Ans)

(D) Ri = 0, R0 = ¥

17. Barichausen criterion for sustained oscillator is

(A) Aβ = 1 Ð00 (Ans)

(B) Aβ = 0

(C) Aβ = 1 Ð1800

(D) A = 1/√β

18. The value of plastic capacitance for a triode may range from

(A) 2 μF to 12 μF

(B) 20 μF to 120 μF

(C) 2 pF to 12 pF (Ans)

(D) 20 pF to 120 pF

19. A colpitts oscillator uses

(A) tapped coil

(B) inductive feedback

(C) tapped capacitance (Ans)

(D) no tuned LC circuit

20. A typical frequency for a RC feedback oscillator is

(A) 1 KHz (Ans)

(B) 100 MHz

(C) 1000 MHz

(D) 1 GHz

21. In pulse transmitter the ratio of time on to time off is called

(A) efficiency

(B) duty cycle (Ans)

(C) base

(D) bandwidth

22. FM broadcast band generally lies in

(A) LF

(B) HF

(C) VHF (Ans)

(D) SHF

23. The following filter is generally used in SSB generation

(A) active filter

(B) mechanical filter (Ans)

(C) LC filter

(D) crystal filter

24. Which is a digital communication system ?

(A) FM

(B) AM

(C) PCM (Ans)

(D) PAM

25. A transistor is basically an amplifying device for

(A) power

(B) voltage

(C) current (Ans)

(D) all of these
7. ### krishnaBanned

April 16, 2013

1. To neglect a voltage source, the terminals across the source are

(A) open circuited

(B) short circuited (Ans)

(C) replaced by some resistance

(D) replaced by an inductor

2. Which is a digital communication system ?

(A) FM

(B) AM

(C) PCM (Ans)

(D) PAM

3. In a resonant circuit, the power factor at resonance is

(A) zero

(B) unity (Ans)

(C) 0.5

(D) 1.5

4. In TV systems the frame frequency is

(A) 100

(B) 60

(C) 50

(D) 25 (Ans)

5. The function 3 s has
(s + 1) (s + 2)

(A) one zero, two poles (Ans)

(B) no zero, one pole

(C) no zero, two poles

(D) one zero, no pole

Solution : G (s) = 3s has one zero at s = 0 and two poles at s = - 1, - 2.
(s + 1) (s + 2)

6. One electron volt is equivalent to

(A) 1.6 * 10-10 J

(B) 1.6 * 10-13 J

(C) 1.6 * 10-16 J

(D) 1.6 * 10-19 J (Ans)

7. Which of the following is donor impurity element ?

(A) Aluminium

(B) Boron

(C) Phosphorous (Ans)

(D) Indium.

8. The diameter of an atom is of the order

(A) 10-6 m

(B) 10-10 m (Ans)

(C) 10-15 m

(D) 10-21 m

9. A transistor is basically an amplifying device for

(A) power

(B) voltage

(C) current (Ans)

(D) all of these

10. If the d.c. valve of a rectified output is 300 V and peak to peak ripple voltage is 10 V, the ripple factor is

(A) 1.18%

(B) 3.33% (Ans)

(C) 3.36%

(D) 6.66%

Solution : rms value of output

= √3002 + 102 = 300.166 V

Average value = 300 V

Form factor RMS value = 300.166 = 1.00055.
Average value 300

Ripple factor = √(Form factor)2 - 1

= √(1.0005)2 - 1 = 0.0333

= 3.33%.

11. Full wave rectifier output has ripple factor of

(A) 1.11 (Ans)

(B) 1.21

(C) 1.41

(D) 1.51

12. In a common base connection IE = 2 mA, IC = 1.9 mA. The value of base current is

(A) 0.1 m (Ans)

(B) 0.2 mA

(C) 0.3 mA

(D) zero

Solution : IE = 2 mA IC = 1.9 mA

Ib = IE - IC = (2 - 1.9) = 0.1 mA.

13. For the action of transistor the base region must be

(A) P-type material

(B) N-type material

(C) very narrow (Ans)

(D) highly doped

14. Compared to a CB amplifier the CE amplifier has higher

(A) current amplification

(B) output dynamic resistance

(C) leakage current

(D) input dynamic resistance

(E) all of the above (Ans)

15. When a transistor is biased to cut-off its Y is

(A) 0.5

(B) 0

(C) 1.0 (Ans)

(D) 0.8

16. An ideal voltage amplifier should have

(A) Ri = 0, R0 = 0

(B) Ri = 0, R0 = ¥

(C) Ri = ¥, R0 = 0 (Ans)

(D) Ri = 0, R0 = ¥

17. Barichausen criterion for sustained oscillator is

(A) Aβ = 1 Ð00 (Ans)

(B) Aβ = 0

(C) Aβ = 1 Ð1800

(D) A = 1/√β

18. The value of plastic capacitance for a triode may range from

(A) 2 μF to 12 μF

(B) 20 μF to 120 μF

(C) 2 pF to 12 pF (Ans)

(D) 20 pF to 120 pF

19. A colpitts oscillator uses

(A) tapped coil

(B) inductive feedback

(C) tapped capacitance (Ans)

(D) no tuned LC circuit

20. A typical frequency for a RC feedback oscillator is

(A) 1 KHz (Ans)

(B) 100 MHz

(C) 1000 MHz

(D) 1 GHz