1 . Draw the structure of a crystal lattice to show the arrangement of electrons in following:

• Pure silicon.
• P-type semiconductors
• N-type semiconductors
  2. Explain how temperatures rise affects the electrical conductivity or pure semiconductors.
  (a)Draw the symbol of a p-n diagram junction diode.
  (b)Use a circuit diagram to distinguish between forward and reserve bias of p-n junction diode.
  3. Use a labelled diagram to explain how a full valve rectification may be achieved by using a resistor and :
• (i) Two diodes.
• (ii) Four diodes.

4. With the aid of a diagram explain how a capacity can be used to smoothen a full wave which has been rectified. Show using a sketch how the smoothened wave will appear on the screen of C.R.O.

5. What is meant by the following terms: semiconductor, intrinsic conduction, extrinsic conduction, doping, donor atoms, acceptor atoms, n-type semiconductor, p type, semiconductor, depletion layer, forward bias, hole, reverse bias and Zener effect?
   6. Explain how doping produces a p-type and an n-type semiconductor.
   7. Distinguish between electronics and electricity.
   8. a) What is rectification?
   (b) With diagrams, describe how half-wave and full-wave rectification can be achieved.
   9. Explain why a diode conducts easily on forward bias and not in reverse bias.