INTRODUCTION

In this fast developing society, ‘Electronics’ has come to stay as the most important branch of engineering. Electronic devices are being used in almost all industries for quality control and automation and they are fast replacing the present vast army of workers engaged in processing and assembling in the factories. Great strides that have been taken in the industrial applications of electronics in the recent years have demonstrated that this versatile tool can be of great importance in increasing production, efficiency and control.

Electronics is the branch of science and technology that deals with current conduction through vacuum or gas or semiconductors . Electronics essentially deals with electronic devices and their utilization. An electronic device is that in which current flows through a vacuum, a gas or a semiconductor. Electronics has gained much importance due to its numerous applications in industry. Some of the applications of electronic devices are,

The conversion of AC to DC is called rectification. Electronic devices can convert AC power to DC with very high efficiency. This DC supply can be used for charging storage batteries, field supply of DC generators, electroplating etc.

The process of raising the strength of a weak signal is known as amplification. Electronic devices can accomplish the job of amplification and thus act as amplifiers. These amplifiers are used in a wide variety of ways like in radio sets, public address systems, televisions etc.

Electronic devices can convert DC power into AC power of any frequency. When performing this function, they are known as oscillators. The oscillators are used in many ways. For example, electronic high frequency is used for annealing and hardening.

Electronic devices can convert light into electricity. This electric current thus generated is called photoelectric current’. Photoelectric devices are used in burglar alarms, sound recording, motion pictures etc.

Electronic devices can convert electricity into light. This property is utilized in picture tube of television sets, radar etc.

The discovery of electricity motivated research and that has lead to the present day concept of an atom. The study of electrical nature of matter was done by JJ Thomson who focused his attention on the passage of electricity through gases. The studies conducted by Thomson on electrical discharge through gases at low pressure established that the atom is composed of charged particles, electrons and protons. The study of electrical discharge marked the beginning of the branch of physics called Atomic Physics.

An atom is the smallest particle of a chemical element possessing all the chemical properties of the element. An atom consists of protons, which are positively charged particles, neutrons, which are neutral particles. The protons and neutrons are housed in the nucleus and the electrons revolve round the nucleus in various orbits. The charge of the nucleus is positive. The charge of the nucleus is equal to the number of protons in it. The charge of a proton is 1.6 x 10^-19coulomb and that of an electron is 1.6 x 10 ^–19 coulomb. Generally each atom is electrically neutral. This means that the number of protons and electrons must be equal. The mass of an electron is 9.107 x 10 ^–31Kg and that of a proton is 1836 times that of an electron. The entire mass of an atom is concentrated in its nucleus. The radius of an atom is of the order of 1Angstrom(10 ^–10meters).