Semiconductors For std 10 CBSE Course

Semiconductors

You know that metals are good conductors of electricity. Substances like glass, plastic, porcelain are insulators. Some substances like germanium and silicon are neither good conductors nor insulators. Their conductivity lies in between that of conductors and insulators. Such substances are called semiconductors.

Conductivity of semiconductors : you know that the atoms of silicon and germanium have four electrons each in their outermost shell. All these electrons are involved in covalent bonding and are not free. Hence these elements should behave like insulators.  

However in these cases, usually a small amount of energy (in the form of heat or light) is sufficient to break a covalent bond and  set and electron free to move. Thus even at room temperatures, a substantial number of electrons will be dissociated from their atoms and this number increases with temperature. This is the reason for these elements exhibiting conductivity.

  Further, when an electron is removed from a covalent bond, it leaves a vacancy, equivalent to positive charge. An electron from a neighbouring atom, can drop into this vacancy, leaving the neighbour with a vacancy. In this way, the vacancy usually called a ‘hole’ can move and serves as an additional ‘charge carrier’ 

Electronics std 10 for CBSE board

ØElectron, a negatively charged particle (charge= 1.6 X 10-19C and mass 9.1 X 10-31 kg) is a common constituent of all matter. Electrons resolve round the nucleus of an atom, in different orbits.

Ø Flow of electrons constitutes electric current.

Ø Substances which allow electric current to pass through them, are called conductors, substances which do not allow electric current to pass through them are called insulators.

ØRadio waves are electromagnetic waves. They are used for communication such as radio broadcasting, television broadcasting, satellite communication etc.

3.1 INTRODUCTION

You have seen radio, T.V., tape recorder, computer and other electronic gadgets. Have you at any time wondered.

why they are called electronic gadgets?

Or

what is meant by electronics?  

The term ‘electronics’ owes its origin to the word ‘electron’. The term originally applied to the study of electron behavior and movement. Later with the advances in the knowledge about the fundamental nature of electron and about the way in which the motion of these particles could be controlled and utilized, the term came to be used in its existing broader sense.

Toady, electronics is a field of physics and engineering (both pure and applied) dealing with the design and application of devices, usually electronic devices. The operation of these depends upon the emission, behavior and effects of electrons. The development in these areas of knowledge has made it possible to manufacture a wide range of consumer, industrial and military products.

The changes that are taking place in the field of electronics, are so rapid that today’s technology may be obsolete tomorrow. Electronics finds applications in almost every walk of life. It has influenced areas such as communication, entertainment, defense, industry and medical science. The most recent advances in electronics include digital circuits, micro processors, digital computers, opto-electronics, laser technology and so on.