Short notes
Objective questions (Answers are given below)
- The total energy of a revolving electron in an
atom can
(a) have any value above zero
(b) never be positive
(c) never be negative
(d) not be calculated. - An atom is said to be ionised when any one of
its orbiting electron
(a) Jumps from one orbit to another
(b) is raised to a higher orbit
(c) comes to the ground state
(d) is completely removed. - The maximum number of electrons which the
M-shell of an atom can contain is
(a) 32 (b) 8
(c) 18 (d) 50. - Electronic distribution of an Si atom is
(a) 2, 10, 2 (b) 2, 8, 4
(c) 2, 7, 5 (d) 2, 4, 8. - Semiconductor materials have ……………..
bonds.
(a) ionic (b) covalent
(c) mutual (d) metallic. - The maximum number of electrons which the
valence shell of an atom can have is
(a) 6 (b) 8
(c) 18 (d) 2 - Silicon has Z = 14. Its outermost orbit is
(a) partially filled
(b) half filled
(c) completely occupied
(d) empty - Major part of the current in an intrinsic
semiconductor is due to
(a) conduction-band electrons
(b) valence-band electrons
(c) holes in the valence band
(d) thermally-generated electron. - Conduction electrons have more mobility than
holes because they
(a) are lighter
(b) experience collisions less frequently
(c) have negative charge
(d) need less energy to move them. - Doping materials are called impurities because
they
(a) decrease the number of charge carriers
(b) change the chemical properties of
semiconductors
(c) make semiconductors less than 100
percent pure
(d) alter the crystal structures of the pure
semiconductors.
- Current flow in a semiconductor depends on
the phenomenon of
(a) drift (b) diffusion
(c) recombination (d) all of the above. - The process of adding impurities to a pure semiconductor
is called
(a) mixing (b) doping
(c) diffusing (d) refining. - The most widely used semiconucting material
in electronic devices is
(a) germanium (b) sillicon
(c) copper (d) carbon - Electon-hole pairs are produced by
(a) recombination (b) thermal energy
(c) ionization (d) doping - Recombination takes place when
(a) an electron falls into a hole
(b) a positive and a negative ion bond together
(c) a valence electron becomes a conduction
(d) a crystal is formed - When a P-N junction is formed, diffusion current
causes
(a) mixing of current carriers
(b) forward bias
(c) reverse bias
(d) barrier potential. - The leakage current of a P-N diode is caused
by
(a) heat energy (b) chemical energy
(c) barrier potential (d) majority carriers. - Electronic components which are made of a
semiconductor material are often called
………………. devices.
(a) solid-state (b) silicon
(c) germanium (d) intrinsic. - Any voltage that is connected across a P-N
junction is called …………. voltage.
(a) breakdown (b) barrier
(c) bias (d) reverse. - The area within a semiconductor diode where
no mobile current carriers exist when it is
formed is called ………. region.
(a) depletion (b) saturation
(c) potential barrier (d) space charge. - The depletion region of a semiconductor diode
is due to
(a) reverse biasing
(b) forward biasing
(c) crystal doping
(d) migration of mobile charge carriers. - If an intrinsic semiconductor is doped with a
very small amount of boron, then in the extinsic
semiconductor so formed, the number of electrons
and holes will,
(a) decrease
(b) increase and decrease respectively
(c) increase
(d) decrease and increase respectively. - Two initially identical samples A and B of pure
germanium are doped with donors to concentrations
of 1 × 1020 and 3 × 1020 repectively. If
the hole concentration in A is 9 × 1012, then the
hole concentration in B at the same temperature
will be
(a) 3 1012 m−3 (b) 7 × 1012 m−3
(c) 11 × 1012 m−3 (d) 27 × 1012 m−3 - Hall effect is observed in a specimen when it
(metal or a semiconductor) is carrying current
and is placed in a magnetic field. The resultant
electric field inside the specimen will be in
(a) a direction normal to both current and
magnetic field
(b) the direction of current
(c) a direction antiparallel to the magnetic
field
(d) an arbitrary direction depending upon
the conductivity of the specimen.
- (b) 2. (d) 3. (c) 4. (b) 5. (b) 6. (b) 7. (b) 8.(a) 9. (d) 10. (d) 11. (d) 12. (b) 13. (b) 14. (b 15(a) 16. (d) 17. (a) 18. (a) 19. (c) 20. (a) 21. (d) 22.(d) 23. (a) 24. (a)