Electronic circuits, 2nd Semester, 2021-2022 Tutorial #1
Electronic circuits
Tutorial #1
Problem 1
Choose the correct answer:
1. Valence electrons are:
(a) in the closest orbit to the nucleus (b) in the most distant orbit from the nucleus
(c) in various orbits around the nucleus (d) not associated with a particular atom
2. A positive ion is formed when:
(a) a valence electron breaks away from the atom (b) two atoms bond together
(c)there are more holes than electrons in the outer orbit (d) an atom gains an extra valence electron
3. The most widely used semi-conductive material in electronic devices is
(a) germanium (b) carbon (c) copper (d) silicon
4. The difference between an insulator and a semiconductor is// (a) a wider energy gap between the
valence band and the conduction band
(b) the number of free electrons
(c) the atomic structure (d) answers (a), (b), and (c)
5. The energy band in which free electrons exist is the
(a) first band (b) second band (c) conduction band (d) valence band
6. Each atom in a silicon crystal has
(a) four valence electrons (b) four conduction electrons
(c) eight valence electrons, four of its own and four shared
(d) no valence electrons because all are shared with other atoms
7. Electron-hole pairs are produced by
(a) recombination (b) thermal energy (c) ionization (d) doping
8. Recombination is when
(a) an electron falls into a hole (b) a positive and a negative ion bond together
(c) a valence electron becomes a conduction electron (d) a crystal is formed
9. he current in a semiconductor is produced by
(a) electrons only (b) holes only (c) negative ions (d) both electrons and holes
10. In an intrinsic semiconductor,
(a) there are no free electrons
(b) the free electrons and holes are thermally produced
(c) there are only holes
11. The process of adding an impurity to an intrinsic semiconductor is called
(a) doping (b) recombination (c) atomic modification (d) ionization
12. A trivalent impurity is added to silicon to create
(a) germanium (b) a p-type semiconductor
(c) an n-type semiconductor (d) a depletion region
13. The purpose of a pentavalent impurity is to
(a) reduce the conductivity of silicon (b) increase the number of holes
(c) increase the number of free electrons (d) create minority carriers
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Electronic circuits, 2nd Semester, 2021-2022 Tutorial #1
14. The majority carriers in an n-type semiconductor are
(a) holes (b) valence electrons (c) conduction electrons (d) protons
15. Holes in an n-type semiconductor are
(a) minority carriers that are thermally produced
(b) minority carriers that are produced by doping
(c) majority carriers that are thermally produced
(d) majority carriers that are produced by doping
16. A pn junction is formed by
(a) the recombination of electrons and holes (b) ionization
(c) the boundary of a p-type and an n-type material (d) the collision of a proton and a neutron
17. The depletion region is created by
(a) ionization (b) diffusion (c) answers (a), and (b)
18. The depletion region consists of
(a) nothing but minority carriers (b) positive and negative ions
(c) no majority carriers (d) answers (b) and (c)
19. When a diode is forward-biased and the bias voltage is increased, the forward current will
(a) increase (b) decrease (c) not change
20. When a diode is forward-biased and the bias voltage is increased, the voltage across the diode will
(a) increase (b) decrease (c) not change
21. When a diode is reverse-biased and the bias voltage is increased, the reverse current will
(a) increase (b) decrease (c) not change
22. The term bias means
(a) the ratio of majority carriers to minority carriers (b) the amount of current across a diode
(c) a dc voltage is applied to control the operation of a device (d) neither (a), (b), nor (c)
23. To forward-bias a diode,
(a) an external voltage is applied that is positive at the anode and negative at the cathode (b) an
external voltage is applied that is negative at the anode and positive at the cathode (c) an external
voltage is applied that is positive at the p region and negative at the n region (d) answers (a) and (c)
24. For a silicon diode, the value of the forward-bias voltage typically
(a) must be greater than 0.3 V (b) must be greater than 0.7 V (c) depends on the width of the depletion
region (d) depends on the concentration of majority carriers
25. A diode is normally operated in
(a) reverse breakdown (b) the forward-bias region
(c) the reverse-bias region (d) either (b) or (c)
Best Wishes,
Dr. Nessim Mahmoud
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