Tulsi Prajna 2003 04

SR No.: 524615
Original Sutra Author: N/A
Author: Shanta Jain, Jagatram Bhattacharya
Publisher: Jain Vishva Bharati
Publication Year: 2003
Total Pages: 122
Language: Hindi
Classification: Magazine, India_Tulsi Prajna, & India
File Size: 6 MB

Page 89

Increase in the temperature of a good conductor results in the increase in its resistivity, but increase in the temperature of a semiconductor (within certain range) results in a decrease in its resistivity. A semiconductor, irradiated by electromagnetic radiation of an appropriate frequency also quite often results in an increase in its conductivity. The electric properties of a substance depend on its crystal structure and its electronic configuration. A large number of semiconducting substances have been produced systematically by preparing suitable compounds. In this chapter, however, we will study only two most important semiconducting elements, Si
and Ge; which have crystal structure of diamond." (c) Kakani, Saxena, Chhajer & Lodha, op.cit, pp. 536–
''Impurities added to pure germanium or silicon will cause a change in the lattice structure, which might add a free electron or create a hole. The importance of hole is that it may serve as a carrier of electricity and a free electron from a neighbouring atom may drop into it."
"The study of transistors is based on semiconductors. Semiconductors which find use in transistors are silicon and germanium, out of which germanium is commonly used.
"When an electric field is applied between both the ends of a semiconductor crystal the free carriers such as free electrons and holes attain drift velocity. The electrons drift towards the positive
electrode and holes move towards the negative electrode." 45. (a) Satish K. Gupta, op.cit pp. 3,4
"In 600 B.C. the Greek philosopher Thales observed that when amber* was rubbed with a woolen cloth, it acquired the property of attracting light objects like feathers of birds, small bits of paper, pieces of dry leaves, etc. In 100 A.D., Dr. William Gilbert was led to the conclusion that there are many other substances like amber, which acquire the property of attracting such light objects after they had been rubbed with some other suitable substances. For example, if on a dry day, we comb dry hair with a rubber comb, the comb acquires the property of attracting the small bits of paper and dry grass. Similarly, a glass rod acquires the attractive property on being rubbed with silk and an ebonite rod on being rubbed
It is hardened sap of a tree similar to a pine tree. In Greek, the meaning of amber is electrum and probably the words like electric charge, electric force, electric potential, electricity and finally electron owe their origin to electrum.
88
=
TAHT 4511 310 120-121