Test Preparation on UGC NET Electronic Science Mock Test-2
Assertion (A) : TWTA is a narrowband device and has a helicalstructure and it is used asamplifier and oscillator.Reason (R) : In TWT, theelectron beam travels through aslow-wave structure and speedof electron beam is110of thevelocity of light.
Assertion (A) : An Op-Amp is adirect coupled high gainamplifier.Reason (R) : It consists of one ormore differential amplifiers andusually followed by a leveltranslator and push pull stage.
Assertion (A) : To have a highsensitivity, a low value ofgauge factor is desirable.Reason (R) : Semi-conductorstrain gauges are made up of Siand Ge and show piezoresistiveeffect.
Assertion (A) : In amplitudemodulation technique themodulation index should beclose to 1.Reason (R) : The power carriedby message signal in the sidebands increases with increasein modulation index.
Assertion (A) : In logic circuit,positive logic is represented bylogic '0' voltage level is lowerthan logic '1' voltage level.Reason (R) : Excess 3 code isknown as self complementarycode.
Assertion (A) : A self-biased circuithas a better stability than afixed bias circuit.Reason (R) : It provides negativefeed back by the use of anadditional resistor between thebase and ground.
Assertion (A) : Optical fibers havebroader bandwidth compared toconventional copper cables.Reason (R) : Low power LASERbeams are considered to bevery powerful as compared tohigh power ordinary lightbeams.
Assertion (A) : A demultiplexer canbe used as a decoder.Reason (R) : A demultiplexer isbuilt by using AND gates only.