History  of Electronics

            The history of electronics is a story  of the twentieth century and three key components-the vaccum tube, the transistor  and the integrated circuit. In  1883 Thomas Alva Edison discovered  the electrons will flow from one metal conductor to another through a vaccum. This discovery of conduction became known as the  Edison effect. In   1904,John Fleming applied the Edison effect in inventing a two element electron tube called a diode and Lee  De forest  followed in 1906  with the three element tube, the friode. These vaccum tubes were the devices that made manipulation of electrical energy possible so it could be amplified and transmitted.

              The first applications of electron tubes were in radio communications. In 1918,Edwin Armstrong  invented the “Super –heterodyne receiver ”that  could  select among radio signals or stations and could receive distant signals Radio broadcasting  grew astronomically in  the 1920 as a direct result.Armstrong also invented wide band  frequency  modelation in 1935;only amplitude modulation had been used from 1920 to 1935.Communications technology was able to make huge advances before world war II as more specialized tubes were made for many applications.

                After the war electron tubes were used to develop the first computers, but they were impractical because of the sizes of the electronic components.In 1947, the transistor was invented by a team of engineers from Beu laboratories. John Barden, walter Brattain, a William shockely received a Nobel prize for their creation, but few could envision how  quickly  and dramatically the transistor would change the world. The transistor functions like the vaccum  tube,but it is tiny by comparision,, weight less, consumes less power, is much more reliable and is cheaper to manufacture with its combination of metal contacts and semiconductor materials.

Applications of Electronics

                 Electronics find applications in almost every walk of life and the applications are continuously  increasing. However the applications are too numerous and varied in nature to be listed here:-

(i)Communication

                 Economic and reliable communication of intelligence or message is vital for the progress of any country. Earlier the principal methods of communication were only line telephony and line telegraphy. Wireless telephony and telegraphy which came a little later enabled us to communicate with any body in any part of the world. Use of satelite makes it possible to establish communication between far remote places.

(ii)Entertainment Electronics

                 Radio and TV broadcast provides entertainment in addition to begin means of communication. Video cassette recorder(VCD) forms another electronic equipments such as tape recorder,recorder player,public address system,stereo systems also constitute means of entertainment.

(iii)Electronics in Defence

                  Today electronics plays vital role in defence.The following are the more important applications of electronics in defence.

1. Line communication over short distance
2. Radio communication(FM or AM) between two or more stations
3. Radar used for detection of fixing of enemy targets such as air craft, ships etc.
4. Communication between different defence units in coded to disallow interception by the enemy
5. Computers are being increasingly used for establishing fast, accurate and reliable communication.

(iv)Electronics in Industry

               The application of electronics in industry are numerous and varied in nature. The following are some of main applications:-

1.  Dielectric and induction heating

ii.    Resistance welding

iii.   Robots used for quick, precise and cheap production of goods

iv.   Ultrasonic for a variety of  industrial and medical applications

v.    Small pocket calculators and desk calculators

(v)Medical applications of Electronics

                    Electronic devices and equipments are being made in medical sciences for diagonosis and treatment of ailments, in prevention of ailments etc.The following are some of the important applications of electronics in medicine:-

1.   X-ray are used for detection of fractures in bone structure, detection of tumors   and in treatment of certain diseases

                 (ii)   Electron microscope is used for study of minute cell structure

                 (iii)  Electro-cardiograms (ECG) are used to record the condition of heart patient

                 (iv)  Electro-encelography (EEG) is used for study of brain diseases.

                  (v)  Electron machines permit visual display of heart beat 

(vi)Instrumentation

                    Electronic instrumentation plays a vital role in industry, laboratories and in research organizations. Typical electronic instruments so used are as below:-

1.    Transistors Voltmeter (TVM) for accurate measurement of voltage

(ii)  Cathode  Ray  Oscilloscope (CRO’s)  for  measurement of  current, voltage  Frequency, phase angle, depth of modulation of amplitude modulated  wave, for display of  waveform etc.

(iii) Frequency counters for measuring frequency of a periodic voltage

(iv)  Digital  multimeters b (DMM)   for measurement of voltage,  current   and    Resistance and for its visual display

(v)     Standard Signal Generators for generating voltages of different frequencies With great accuracy

(vi)     Power- meter for measurement of power