ELECTRONIC DEVICES
(OTQs)
1.In the depletion region of a p-n junction, there is a shortage of ……..
(a)Acceptor ions
(b)Holes and electrons
(c)Donor ions
(d)None of the above
2.For a pure semiconductor the Fermi level is:
(a) in the conduction band
(b) near the centre of the gap between the valence and conduction bands
(c) in the valence band
(d) well below the valence band
3. Hole is
(a). an anti-particle of electron
(b). a vacancy created when an electron leaves a covalent bond
(c). absence of free electron
(d). an artificially created particle
4. At room temperature relation between number of holes and electrons in pure silicon crystal
is
(a) n e> n h (b) ne< nh (c) ne= nh (d) ne ≥ nh
5. When an electric field is applied across a semiconductor
(a) electrons move from lower energy level to higher energy level in the conduction
band. (b) electrons move from higher energy level to lower energy level in the
conduction band.
(c) holes in the valence band move from higher energy level to lower energy level.
(d) holes in the valence band move from lower energy level to higher energy level.
6. The reverse bias current ______ with the increase of temperature.
(a) decreases (b) increases (c) remains same (d) none of the
above
7. Which one of the following represents forward bias diode?
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8. In an unbiased p-n junction, holes diffuse from p- region to n-region because (a) free
electrons in the n-region attract them.
(b) they move across the junction by the potential difference.
(c) hole concentration in p-region is more as compared to n-region.
(d) all the above.
9. The I-V characteristics of an LED is
10. When semiconductor is heated its resistance
(a) Increases (b) Decreases
(c) Remains constant (d) nothing is definite.
11. The current obtain from simple filter less full wave rectifier is
(a) Varying direct current (b) Constant direct current
(c) Half current (d) Eddy current
12. The symbol of photocell:
(a) (b)
(c) (d)
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13.In the following diode circuit
(a)D1 and D2 are reverse biased
(b)D1 and D2 are forward biased
(c) D1 is reverse biased and D2 is forward biased
(d) D2 is reverse biased and D1 is forward biased
14. The diffused impurities with ______________ valance electrons are called acceptor
atoms.
(a) 0 (b) 3 (c) 4 (d) 5
.
15. At what temperature would an intrinsic semiconductor behave like a perfect insulator?
16. Name the two processes involved in the formation of p-n junction
17. Draw V-I characteristics of a p-n junction diode in
(a) forward bias (b) reverse bias
18. In reverse biasing condition barrier potential of p-n junction diode_________.
19. Draw input and output waveforms for full- wave rectifier.
20. Why would photodiode be operated at reverse bias?
21. Draw the symbol indicating (i) Zener diode (ii) photodiode
22. Why Si and GaAs are most commonly used in making of a solar cell?
23. Draw energy band diagram for a (i) p- type extrinsic semiconductor (ii) n-type extrinsic
semiconductor.
24. The device used to obtain steady d c voltage from pulsating voltage is called__________.
25. Majority charge carriers in p type semiconductor are ________.
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26. The depletion width of p- n junction _____________ in the forward bias condition.
27. Addition of _____________impurity to a semiconductor creates many holes.
28. A rectifier converts ________ to __________.
29. The colour of light emitted by a LED depends on its __________.
30. The reverse saturation current level is typically measured in _________.
Accepted Answers
1(b) 2(b) 3(b) 4(c) 5(a) 6(b) 7(a) 8(c) 9(a) 10(b) 11(a) 12(d) 13(c) 14(b)
15 0 Kelvin
16 diffusion and drift
17
18 increases
19
20 it converts incident light to electric current more effectively in reverse bias condition than in
forward bias condition. The width of depletion region is more in reverse bias than forward
bias, in which photos are absorbed and electron hole pairs are generated.
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21 ,
22 (i) ideal band gap (ii) high electrical conductivity and high optical absorption
23
24 rectifier
25 holes
26 decreases
27 trivalent 28 A.C. to D.C.
29 composition and energy gap
30 µA
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