Engineering Chemistry S Datta

SOLID STATE CHEMISTRY 503
Comment
Thus output voltage is 96 times the input voltage. If the output voltage is applied to a second
transistor it is increased still more. By increasing the number of transistors the voltage may
be increased indefinitely.
EXERCISES
1. Distinguish between (a) crystalline solids and amorphous solids, (b) semiconductors and insulators.
2. Explain: (a) plane of symmetry, (b) centre of symmetry, (c) axis of symmetry.
3. Explain Band Theory.
4. Explain the role of silicon and germanium in the field of semiconductors.
5. Explain the terms—amorphous and crystalline solids.
6. How can electrical conductivity to metal be explained on the basis of bond theory?
7. How many symmetry elements are there in a simple cube system?
8. What do you mean by solid defect? Describe (a) Frenkel defect and (b) Schottky defect.
9. Define the laws of crystallography.
10. Define transistors.
11. Describe conductors, semiconductors and insulators in the light of band theory.
12. What do you mean by doping agent?
13. What is the utility of doping agent in a semiconductor?
14. Explain with the neat diagram (a) working of a PNP and (b) working an NPN transistor.
15. What is a rectifier? What is its application?
16. What do you mean by a photovoltaic cell? Explain its working principle and uses.
17. If density of NaCl is 2.163 g cm –3 , find the spacing between the planes parallel to the cubic
lattice faces of the sodium chloride crystal (2.83 Å).
18. Calculate the density of copper. Copper has FCC structure and lattice constant is 3.61 Å unit
(Cu = 63.54) (8.98 g cm –3 ).
19. Show that for BCC and FCC crystals the lattice constants are given by
a BCC
= 4 r
3
where r is the atomic radius.
a FCC
= 4 r
2