BSNL JTO RADIO ENGINEERING EXAM PAPERS I BSNL JTO TELECOM EXAM PAPERS I BSNL JTO ELECTRONICS SOLVED PAPERS I

BSNL JUNIOR TELECOM OFFICER (JTO)

Electronics & Communication

Solved Paper For Competitive Exams

Q.1.Reactive current through the capacitive load produces -

• Magnetic field
• Electric field
• Supermagnetic field
• None

Q.2.One of the following which gives piero-electric effect is -

• Mu metal
• PVDF
• Sapphire
• Ferrites

Q.3.PZT piezo- electric materials have -

• Higher curie temperature
• Lower curie temperature
• Absolute temperature
• None

Q.4.The residual resistivity of a binary alloy at OK is -

• The sum of the residual resistivities of the component metals
• The difference of the residual resistivities of the component metals.
• The product of the residual resistivities of the component metals
• Dependent on the concentration of the minor component in the alloy

Q.5.In active filter circuits, inductances are avoided mainly because they -

• Are always associated with some resistance
• Are bulky and unsuitable for miniaturisation
• Are non-linear in nature
• Saturate quickly 

Q.6.The depletion layer across a p-n junction lies -

• mostly in the p-region
• mostly in the n-region
• equally to both p and n region
• entirely in the p-region

Q.7.The voltage induced in a loop of wire rotating in a strong and steady magnetic field is -

• pulsating dc
• dc
• rectified ac
• ac 

Q.8.One of the following types of capacitor which is polarized is -

• Electrolytic
• Ceramic
• Paper
• Mylar 

Q.9.Electric shock is-

• Always fatal
• Never fatal
• Sometimes fatal
• Always disfiguring

Q.10.A typical value of filter capacitor for 50 Hz ripple is -

• 16mF
• 10F
• 10mF
• None 

Q.11.A telephone relay armature is made of material with -

• High electrical conductivity
• Low electrical conductivity
• Negligible conductivity
• None 

Q.12.Larger the value of filter capacitor -

• Larger is the peak-peak value of ripple voltage
• Larger is the peak current in the rectifying diode
• Longer is the time that current pulse flows through the diode
• Smaller is the dc voltage across the load

Q.13.Barrier potential in a P-N junction is caused by -

• Thermally generated electrons and holes
• Diffusion of majority carriers across the junction
• Migration of minority carriers across the junction
• Flow of drift current

Q.14.The polarity of VGS for E-only MOSFET is -

• positive
• negative
• zero
• depends on P or N channel 

Q.15.The following which will serve as a donor impurity in silicon -

• Boron
• Indium
• Germanium
• Antimony 

Q.16.When bias applied to a vari-cap diode is increased, its capacitance -

• is decreased
• is increased
• remains constant
• first increases and then decreases.

Q.17.In case of a bipolar transistor a is -

• positive and greater than 1
• positive and less than 1
• negative and greater than 1
• negative and less than 1 

Q.18.A BJT is -

• not very sensitive to radiations
• very sensitive to radiations.
• independent of radiations
• none 

Q.19.An SCR may be considered to be -

• 2 diodes
• 3 diodes
• 4 diodes
• 5 diodes 

Q.20.For a BJT, under the saturation condition -

• IC = bIB
• IC > bIB
• IC is independent of all other parameters
• IC < bIB

Q.21.In modern MOSFET’s the material used for the gate is -

• High purity silicon
• High purity silica
• Heavily doped polycrystalline silicon
• Epitaxial grown silicon 

Q.22.When the source in the circuit shown is a sinusoidal source then the input voltage is -

• 10V
• 5V
• 27V
• 24V 

Q.23.The voltage transfer ratio of two-port networks connected in cascade may be conveniently obtained from the -

• product of the individual ABCD matrices of the two networks
• product of voltage transfer ratios of the two individual networks
• sum of the Z- matrices of the two networks
• sum of the h – matrices of the two networks 

Q.24.An attenuator drops a 10V signal to 50mv in an experiment. The loss in decibels is -

• –40dB
• –6dB
• –55dB
• –60dB 

Q.25.When the network has 10 nodes and 17 branches then the number of different node pair voltages would be -

• 7
• 9
• 10
• 45 

Q.26.The circuit shown in the following fig. will act as an ideal current source with respect to terminals A and B when frequency is -

• zero
• 1rad/s
• 4rad/s
• 16rad/s 

Q.27.When a short vertical grounded antenna is required to radiate at 1MHz and the effective height of the antenna is 30 m then the calculated value of the radiation resistance is -

• 1.58 W
• 158 W
• 15.8 W
• None of these

Q.28.Shannon’s law relates -

• antenna gain to bandwidth
• frequency to antenna gain
• antenna gain to transmission losses
• information carrying capacity to S/N ratio

Q.29.One of the following modes which has the characteristic of attenceation becoming less as the frequency is increased and is attractive at  microwave frequencies of circular cylindrical wave guides is -

• TE1 mode
• TM01 mode
• TE01 mode
• Higher order mode 

Q.30.For a transmission line, the propogation constant, for a TEM wave travelling in it is given by (Where the symbols have the usual meanings ) -

• a)   [ (R+jL) (G+jc)
• b)  [ R+jL) (G+jc)] ½
• c)   [ (R-jL) (G + jc) ] ½
• d)  [(R-jL) ( G+j2c)1/3

Q.31.The advantages of wave guides over co-axial lines would include which of the following features-
1. Easier to use  
2. lower power losses
3. Higher operating frequencies possible

• 1 and 2
• 1 and 3
• 2 and 3
• 1,2 and 3 

Q.32.When a 75 ohm transmission line is to be terminated in two resistive loads R1 and R2 such that the standing pattern in the two cases have the same SWR , then the values of R1 and R2  (in ohms) should be -

• 250 and 200 respectively
• 225 and 25 respectively
• 100 and 150 respectively
• 50 and 125 respectively

Q.33.The degenerate modes in a wave guide are characterized by -

• Same cut off frequencies but different field distribution
• Same cut off frequencies and same field distributions
• Different cut off frequencies but same field distributions
• Different cut off frequencies and different field distributions

Q.34.A TEM wave impinges obliquely on a dielectric-dielectric boundary with Er1=2 and Er2=1, the angle of incidence for total reflection is -

• 30
• 60
• 45
• 90

Q.35.The radiation  pattern  of Hertzian dipole in the plane perpendicular to the dipole is a -

• Null
• Circle
• Figure of eight
• None of the above

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