05-01-2018, 04:31 PM
ELECTRONICS & TELECOMMUNICATION
*The study of the behaviour of electrons, their control and use is known as Electronics.
*An electronic device which has the semiconducting property that allows current to flow in one direction only -Diode
*The simplest form of a vacuum tube is diode.
*The emission of electrons from a strongly heated surface is called Thermionic emission.
*Vacuum tubes or valves work on the principle of - Thermionic emission.
*A thermionic valve having three electrodes namely cathode, anode and grid is known as Triode.
*Now-a-days thermionic valves are completely replaced by Transistors
*Wonder Baby of Electronics - Transistor
*Semiconductor device used to amplify or
*switch electronic signals and electrical power -Transistor
*Transistor was invented by John Bardeen, W.H. Brattain, and William Shockley.
*Triode was invented by Lee De Forest.
*The concept of radio transmission was first demonstrated by the famous Indian scientist
Ans : J.C. Bose
Semiconductors
*Material whose conductivity falls between conductor and insulator
Ans : Semiconductor
*Semi conductors in their pure state are called intrinsic semiconductors
*In intrinsic semicdnductors, number of holes is equal to number of electrons.
*The process of adding controlled impurities to a pure semiconductor is known as doping.
*The impurities which change its electrical property are called dopants.
*Examples for dopants - arsenic, gallium
*Doping improves the conductivity of a semi conductor.
*An intrinsic semiconductor doped with impurity is known as extrinsic semh conductor.
*Extrinsic semiconductors are of two types :
1.N- type semiconductor
2.P-type semiconductor
*The charge carriers in N-type semiconductor
Ans : Free electrons
*The charge carriers in P-type semiconductors
Ans : Holes.
*Semi conductors are used in Photovoltaic cells (solar cells), diodes, transistors and integrated circuits (IQ.
*Diode is mostly used to convert AC to DC. So a diode functions as a rectifier.
*Zener dioide is used as a voltage regulator device which maintains a constant voltage.
*ELINT is the Electronic Intelligence.
*Semiconductors which can be used in Solar cells
Ans : Silicon.
*A very large number of components like diodes, transistors, condensers of capacitors and resistors are incorporated in a single chip.
*A device used to store electric charge consisting of one or more pairs of conductor separated by an insulator
Ans : Capacitor