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BSNL TTA 2008 Sample PapersIf the voltage applied across a capacitance is triangular in waveform then the waveform of the current is-a) Triangularb) Trapezoidalc) Sinusoidald) RectangularAnswer is :- Rectangular1. One of the following statement which is true for relative dielectric constant is -a) It is dimensionlessb) It is not equal to unity for vacuumc) It?s value for all substances is less than oned) NoneAnswer is :- It is dimensionless2. Pure metals generally have-a) high conductivity and low temperature coefficientb) high conductivity and large temperature coefficientc) low conductivity and zero temperature coefficientd) low conductivity and high temperature coefficientAnswer is :- high conductivity and large temperature coefficient3. For small size, high frequency coils, the most common core material isa) Airb) Ferritec) Powdered iond) SteelAnswer is :- Air4. For an abrupt junction Varactor diode, the dependence of device capacitance (C) on applied reverse bias (V) is given by-a) C a V1/3b) C a V-1/3c) C a V1/2d) C a V-1/2Answer is :- C a V-1/35. A superconductor is a-a) A material showing perfect conductivity and Meissner effect below a critical temperatureb) A conductor having zero resistancec) A perfect conductor with highest dimagnetic susceptibilityd) A perfect conductor which becomes resistive when the current density through it exceeds a critical valueAnswer is :-A material showing perfect conductivity and Meissner effect below a critical temperature6. When a semiconductor based temperature transducer has a temperature coefficient of ?2500 mV/0C then this transducer is indeed a-a) Thermistorb) Forward biased pn junction diodec) Reverse biased pn junction dioded) FETAnswer is :- Forward biased pn junction diode7. The location of lightning arrestor is -a) Near the transformerb) Near the circuit breakerc) Away from the transformerd) NoneAnswer is :- Near the transformer8. Time constant of an RC circuit increases if the value of the resistance is -a) Increasedb) Decreasedc) Neither a nor bd) Both a and bAnswer is :- Increased9. Intrinsic semiconductors are those which -a) Are available locallyb) Are made of the semiconductor material in its purest fromc) Have more electrons than holesd) Have zero energy gapsAnswer is :- Are made of the semiconductor material in its purest from10. The primary control on drain current in a JFET is exerted by -a) Channel resistanceb) Size of depletion regionsc) Voltage drop across channeld) Gate reverse biasAnswer is :- Gate reverse bias11. The electrical conductivity of metals which is expressed in ohm-1 m-1 is of the order of -a) 1010b) 105c) 10-4d) 10-6Answer is :- 10512. When biased correctly, a zener diode ?a) acts as a fixed resistanceb) has a constant voltage across itc) has a constant current passing through itd) never overheatsAnswer is :- has a constant voltage across it13. The current amplification factor adc is given by ?a) IC/IEb) IC/IBc) IB/ICd) IB/ICAnswer is :- IC/IE14. Compared to bipolars, FETs have-a) high input impedanceb) low input impedancec) same input impedanced) noneAnswer is :- high input impedance15. The source-drain channel of JFET is -a) ohmicb) bilateralc) unilaterald) both a and bAnswer is :- both a and b16. diac is equivalent to a -a) Pair of SCRsb) Pair of four layer SCRsc) Diode and two resistorsd) Triac widthAnswer is :- Pair of four layer SCRs17. 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/cm3b) 103/ cm3c) 1010/ cm3d) 1012/ cm3Answer is :- 103/ cm318. 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 lawb) Norton?s theoremc) Thevenin?s theoremd) Superposition theoremAnswer is :- Superposition theorem19. One of the following modes which has the characteristics of attenuation becoming less as the frequency is increased and is attractive at microwave frequencies of circular cylindrical wave guides is ?a) TE1 modeb) TM01 modec) TE01 moded) Higher order modeAnswer is :- TE01 mode20. A two-port network is symmetrical if ?a) z11z22 ? z12z21 = 1b) h11h22 ? h12h21 = 1c) AD ? BC = 1d) y11y22 ? y12y21 = 1Answer is :-AD ? BC = 121. For transmission line load matching over a range of frequencies, it is best to use a-a) balunb) broad band directional couplerc) double stubd) single stub of adjustable positionAnswer is :- double stub22. 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 networkb) as an RC driving point impedancec) as an RC driving point admittanced) only by an RLC networkAnswer is:- only by an RLC network23. 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 Cb) L and Cc) R and Ld) R, L and CAnswer is :- L and C24. For a two port reciprocal network, the output open circuit voltage divided by the input current is equal to ?a) Bb) Z12c) ?d) h12Answer is :- Z1225. 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.Answer is :-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.For more Questions please visit www.solvedquestionpapers.com