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BSNL Placement Papers
Posted Date: 01 Jan 2008 Resource Type: Articles/Knowledge Sharing Category: Placement Papers
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Posted By: sachin chaintha Member Level: Silver
Rating:  Points: 5
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One of the following statement which is true for relative dielectric constant is -
a) It is dimensionless
b) It is not equal to unity for vacuum
c)) It’s value for all substances is less than one
d)) None
Pure metals generally have-
a) high conductivity and low temperature coefficient
b) high conductivity and large temperature coefficient
c) low conductivity and zero temperature coefficient
d) low conductivity and high temperature coefficient
For small size, high frequency coils, the most common core material is
a) Air
b) Ferrite
c) Powdered ion
d) Steel
For an abrupt junction Varactor diode, the dependence of device capacitance (C) on applied reverse bias (V) is given by-
a) C a V1/3
b) C a V-1/3
c) C a V1/2
d) C a V-1/2
A superconductor is a-
a) A material showing perfect conductivity and Meissner effect below a critical temperature
b) A conductor having zero resistance
c) A perfect conductor with highest dimagnetic susceptibility
d) A perfect conductor which becomes resistive when the current density through it exceeds a critical value
When a semiconductor based temperature transducer has a temperature coefficient of –2500 mV/0C then this transducer is indeed a-
a) Thermistor
b) Forward biased pn junction diode
c) Reverse biased pn junction diode
d) FET
The location of lightning arrestor is -
a) Near the transformer
b) Near the circuit breaker
c) Away from the transformer
d) None
Time constant of an RC circuit increases if the value of the resistance is -
a) Increased
b) Decreased
c) Neither a nor b
d) Both a and b
Intrinsic semiconductors are those which -
a) Are available locally
b) Are made of the semiconductor material in its purest from
c) Have more electrons than holes
d) Have zero energy gaps
The primary control on drain current in a JFET is exerted by -
a) Channel resistance
b) Size of depletion regions
c) Voltage drop across channel
d) Gate reverse bias
The electrical conductivity of metals which is expressed in ohm-1 m-1 is of the order of -
a) 1010
b) 105
c) 10-4
d) 10-6
When biased correctly, a zener diode –
a) acts as a fixed resistance
b) has a constant voltage across it
c) has a constant current passing through it
d) never overheats
The current amplification factor adc is given by –
a) IC/IE
b) IC/IB
c) IB/IC
d) IB/IC
Compared to bipolars, FETs have-
a) high input impedance
b) low input impedance
c) same input impedance
d) none
The source-drain channel of JFET is -
a) ohmic
b) bilateral
c) unilateral
d) both a and b
A diac is equivalent to a -
a) Pair of SCRs
b) Pair of four layer SCRs
c) Diode and two resistors
d) Triac width
When a sample of N type semiconductor has electron density of 6.25 ´ 1011 /cm3 at 300K and if the intrinsic concentration of carriers in this sample is 2.5 ´ 1013/cm3 then the hole density will be –
a) 106/cm3
b) 103/ cm3
c) 1010/ cm3
d) 1012/ cm3
When the two networks shown in fig. are equivalent with respect to the terminals 1 and 2 at all frequencies then the values of CA, LB, LC and CC will be –
a) 0.5, 0.33, 6, 0.166
b) 0.5, 3, 6, 0.66
c) 0.5, 3, 3, 2
d) 0.5, 3, 6, 0.166
The statement ,In any network of linear impedances, the current flowing at any point is equal to the algebraic sum of the currents caused to flow at that point by each of the sources of emf taken separately with all other emf,s reduced to zero’ represents -
a) Kirchhoff,s law
b) Norton,s theorem
c) Thevenin,s theorem
d) Superposition theorem
One of the following modes which has the characteristics of attenuation becoming less as the frequency is increased and is attractive at icrowave frequencies of circular cylindrical wave guides is –
a) TE1 mode
b) TM01 mode
c) TE01 mode
d) Higher order mode
A two-port network is symmetrical if –
a) z11z22 – z12z21 = 1
b) h11h22 – h12h21 = 1
c) AD – BC = 1
d) y11y22 – y12y21 = 1
For transmission line load matching over a range of frequencies, it is best to use a-
a) balun
b) broad band directional coupler
c) double stub
d) single stub of adjustable position
The poles and zeros of a driving point function of a network are simple and interlace on the negative real axis with a pole closest to the origin. It can be realised -
a) by an LC network
b) as an RC driving point impedance
c) as an RC driving point admittance
d) only by an RLC network
Poles and zeros of a driving point function of a network are simple and interlace on the jw axis. The network consists of elements –
a) R and C
b) L and C
c) R and L
d) R, L and C
For a two port reciprocal network, the output open circuit voltage divided by the input current is equal to –
a) B
b) Z12
d) h12
In a short electric doublet the radiation properties are so that-
a) The induction field diminishes as the square root of the distance and is only appreciable in the vicinity of the conductor.
b) In the radiation, magnetic field is minimum when the current is maximum.
c) The radiation resistance of a short doublet antenna is extremely high.
d) Mean rate of power through a unit area of spherical sphere surrounding this doublet is proportional to the square of the elemental length, other factors remaining constant.
The frequency modulated (FM) radio frequency range is nearly -
a) 250 –300 MHz
b) 150 – 200 MHz
c) 90 – 105 MHz
d) 30-70 MHz
In an underground cable the distortion in the transmission of carrier frequency can be eliminated by using -
a) Inductive loading
b) Resistive loading
c) Capacitive loading
d) Shielding
The charachteristic impendance of a transmission line with inductance 0.294 mH /m and capacitance 60 pF/m is -
a) 49 W
b) 60 W
c) 70 W
d) 140 W
One of the following statements which is not true for a strip line compared to a waveguide is –
a) It can be directly connected to semiconductor microwave devices
b) It is much smaller in size
c) It has a smaller bandwidth
d) Losses are less
For a quarter wavelength ideal transmission line of characteristic impedance 50 ohms and load impedance 100 ohms, the input impedance will be –
a) 25W
b) 50W
c) 100W
d) 150W
The depth of penetration or skin depth for an electromagnetic field of frequency ‘f’ in a conductor of resistivity r and permeability m is-
a) inversely proportional to r and f and directly proportional to m
b) directly proportional to r and inversely proportional to f and m
c) directly proportional to f and inversely proportional to r and m
d) inversely proportional to r and m and directly proportional to f
When an antenna has a gain of 44dB then assuming that the main beam of the antenna is circular in cross-section the beam width will be -
a) 0.4456 0
b) 1.44560
c) 2.44560
d) 3.44560
Lens antennas used for microwaves are usually made of -
a) Polystyrene
b) Glass of low refractive index
c) Paraboloid surfaces
d) Dielectric media having large refractive index
One of the following types of instrument which is an electrometer is -
a) Electrodynamometer
b) PMMC
c) Electrostatic
d) Moving iron
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