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ECE Objective Questions { Semiconductor Physics and Diodes }

15. At 0?K, a pure semiconductor behaves like an insulator because
A. drift velocity of free electrons is very small
B. energy possessed by electrons at that low temperature is almost zero
C. there is no recombination of electrons with holes
D. no free electrons are available for current conduction

16.  The energy gap is much more in silicon than in germanium because
A. its crystal has much stronger bonds called ionic bonds
B. its valence electrons are more tightly bound to their parent nuclei
C. it has high atomic mass number
D. it has less number of electrons

17. The temperature coefficient of an intrinsic semiconductor is
A. positive
B. negative
C. zero
D. like that of metals

18.  Barrier potential in a P-N junction is caused by
A. thermally-generated electrons and holes
B. diffusion of majority carriers across the junction
C. migration of minority carriers across the junction
D. flow of drift current

19. The forward region of a semiconductor diode characteristic curve is where diode appears as
A. a constant-current source
B. a capacitor
C. an OFF switch
D. an ON switch

20.  The peak inverse voltage (PIV) is applied across a diode when it is
B. on a heat sink
C. reverse-biased
D. forward-biased

21. When biased correctly, a Zener diode
A. acts as a fixed resistance
B. has a constant voltage across it
C. hasa constant current passing through it
D. never overheats

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