18. Measurement of Hall coefficient enables the determination of: A. Mobility of charge carriers B. Type of conductivity and concentration of charge carriers C. Temperature coefficient and thermal conductivity D. None of the above 19. In a p-type semiconductor, the conductivity due to holes (op) is equal to (e is the charge of hole, up is the hole mobility, p0 is the hole concentration): A. po.e/ p B. p/po.e C. po.e.up D. None of the above Hall Effect 20. At room temperature, the current in an intrinsic semiconductor is due to A. Holes B. Electrons C. Holes and electrons D. None of the above 21. If the drift velocity of holes under a field gradient of 100V/m is 5m/s, the mobility (in the same SI units) is A. nhth> nelle 2 B. nhuth>nelle C. nhunelle 2 D. None of the above