Electronic Device Physics Quiz | objective questions | Physics General Knowledge Questions | MCQ | Electronic device and communication

Electronic Device Physics Quiz | objective questions | Physics General Knowledge Questions | MCQ | Electronic device and communication

1 >>basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc are ?

• (A) metals
• (B) insulators
• (C) semiconductors
• (D) conductors

Solution metals are used as basic material in present solid state device.

2 >>In the case of metals the valence and conduction bands have ?

• (A) no overlap, energy gap is small
• (B) no overlap, energy gap =0
• (C) no overlap, energy gap is large
• (D) overlap, energy gap =0

Solution In the case of metals the valence and conduction bands have no overlap, energy gap is small

3 >>In the case of semiconductors the valence and conduction bands have ?

• (A) overlap, energy gap =0
• (B) no overlap, energy gap =0
• (C) no overlap, energy gap is large
• (D) no overlap, energy gap is small

Solution In the case of semiconductors the valence and conduction bands have no overlap, energy gap is small

4 >>Hole is a vacancy or lack of an electron and can travel through the material. It can ?

• (A) None of these
• (B) move only if an electron stops
• (C) serves as an additional current carrier
• (D) only serves as a vacant spot and cannot conduct current

Solution Hole is a vacancy or lack of an electron and can travel through the material. It can only serves as a vacant spot and cannot conduct current

5 >>In a pure, or intrinsic, semiconductor, valence band holes and conduction-band electrons are always present ?

• (A) in equal numbers
• (B) None of these
• (C) such that number of electrons is greater than the number of holes
• (D) such that number of holes is greater than the number of electrons

Solution An intrinsic semiconductor is an undoped semiconductor. This means that holes in the valence band are vacancies created by electrons that have been thermally excited to the conduction band, as opposed to doped semiconductors where holes or electrons are supplied by a “foreign” atom acting as an impurity.

6 >>doping of semiconductor is the process of ?

• (A) removing impurity elements
• (B) adding a surface coating
• (C) None of these
• (D) adding of impurity elements

Solution Doping is the process of adding impurities to intrinsic semiconductors to alter their properties. Normally Trivalent and Pentavalent elements are used to dope Silicon and Germanium. When a intrinsic semiconductor is doped with Trivalent impurity it becomes a P-Type semiconductor.

7 >>Motion of hole is a convenient way of describing ?

• (A) the actual motion of conduction electrons
• (B) the actual motion of energy gap
• (C) the actual motion of free electrons
• (D) the actual motion of bound electrons

Solution Motion of hole is a convenient way of describing the actual motion of bound electrons

8 >>The total current in a semiconductor is ?

• (A) hole current only
• (B) the sum of electron and hole currents
• (C) the difference of electron and hole currents
• (D) electron current only

Solution This current is called the diffusion current. The drift current and the diffusion current make up the total current in the conductor. The change in the concentration of the carrier particles develops a gradient. Due to this gradient, an electric field is produced in the semiconductor.

9 >>In n-type semiconductor the fifth electron ?

• (A) is not capable of moving
• (B) is not present
• (C) needs high energy to be set free
• (D) needs low energy to be set free

Solution Impurity atoms with 5 valence electrons produce n-type semiconductors by contributing extra electrons.

10 >>In n-type semiconductor the total number of conduction electrons n_e is due to the, ?

• (A) holes contributed by donors and those generated intrinsically
• (B) electrons contributed by donors and those generated intrinsically
• (C) electrons generated intrinsically only
• (D) holes generated intrinsically only

Solution total conduction electrons are contributed by donors and those generated intrinsically

11 >>in n-type semiconductor majority carriers and minority carriers are respectively ?

• (A) germanium and silicon
• (B) aluminium and boron
• (C) electrons and holes
• (D) holes and electrons

Solution in n-type semiconductor majority carriers and minority carriers are respectively electrons and holes

12 >>in p-type semiconductor the dopant is ?

• (A) always germanium
• (B) always silicon
• (C) acceptor
• (D) donor

Solution in p-type semiconductor the dopant is acceptor

.13 >>in p-type semiconductor ?

• (A) n_he
• (B) n_h>>n_e
• (C) n_h>n_e
• (D) n_h=n_e

Solution The addition of trivalent impurities such as boron, aluminium or gallium to an intrinsic semiconductor creates deficiencies of valence electrons,called holes. It is typical to use B2H6 diborane gas to diffuse boron into the silicon material.14 >>The electron and hole concentration in a semiconductor in thermal equilibrium is given by ?

• (A) n_en_h=2n²_i
• (B) 2n_en_h=n²_i
• (C) n_en_h=n²_i
• (D) n_en_h=2n³_i

Solution The electron and hole concentration in a semiconductor in thermal equilibrium is given by 2nenh=n2i

15 >>Diffusion in a p-n junction is due to ?

• (A) concentration gradient
• (B) carrier injection
• (C) None of these
• (D) minority carriers

Solution Diffusion in a p-n junction is due to concentration gradient

16 >>Depletion region (space charge) is formed because ?

• (A) majority carriers while diffusing to the other side leave behind immobile ionized atoms
• (B) majority carriers while diffusing to the other side leave behind highly mobile ionized atoms
• (C) majority carriers while drifting to the other side leave behind immobile ionized atoms
• (D) minority carriers while diffusing to the other side leave behind immobile ionized atoms

Solution In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile charge carriers have been diffused away

17 >>In a p-n junction, as the diffusion process continues the width of the depletion zone ?

• (A) remain same
• (B) decrease
• (C) oscillate
• (D) decrease

Solution In a p-n junction, as the diffusion process continues the width of the depletion zone decreases

18 >>Which of the following is not a semiconductor? ?

• (A) Si
• (B) Ge
• (C) As
• (D) All of these

Solution As is not a semiconductor

19 >>In a semiconductor, the forbidden energy gap between the valance band and the conduction band is of the order of ?

• (A) 15ev
• (B) 5ev
• (C) 1 Mev
• (D) Mev

Solution The forbidden gap between the valence band and conduction band is very large in insulators. The energy gap of insulator is approximately equal to 15 electron volts (eV). The electrons in valence band cannot move because they are locked up between the atoms.

20 >>The main difference between conductors, semiconductors and insulators is because of ?

• (A) Work function
• (B) Width of forbidden energy gap
• (C) energy of electrons
• (D) Mobility of electrons

Solution The main difference between conductors, semiconductors and insulators is because of Width of forbidden energy gap

21 >>In an insulator, the forbidden energy gap between the valance band and conduction band is of the order of ?

• (A) 1 ev
• (B) 5 ev
• (C) 10^-3 ev
• (D) 2 Mev

Solution In an insulator, the forbidden energy gap between the valance band and conduction band is of the order of 5ev

22 >>When the conductivity of a semiconductor is only due to breaking of the covalent bonds, the semiconductor is called ?

• (A) extrinsic
• (B) donor
• (C) intrinsic
• (D) acceptor

Solution An intrinsic semiconductor is an undoped semiconductor. This means that holes in the valence band are vacancies created by electrons that have been thermally excited to the conduction band, as opposed to doped semiconductors where holes or electrons are supplied by a “foreign” atom acting as an impurity.

23 >>A small impurity is added to germanium to get p-type semiconductor. This impurity is a ?

• (A) Bivalent substance
• (B) Monovalent substance
• (C) Trivalent substance
• (D) Pentavalent substance

Solution A small impurity is added to germanium to get p-type semiconductor. This impurity is a Trivalent substance

24 >>To obtain a p-type germanium semiconductor, it must be doped with ?

• (A) An
• (B) In
• (C) As
• (D) P

Solution To obtain a p-type germanium semiconductor, it must be doped with As

25 >>The impurity atoms with which pure silicon should be doped to make a p-type semiconductor are those of ?

• (A) Bi
• (B) B
• (C) An
• (D) P

Solution The impurity atoms with which pure silicon should be doped to make a p-type semiconductor are those of B

26 >>When arsenic is added as an impurity to silicon, the resulting material is ?

• (A) p-type semiconductor
• (B) n-type semiconductor
• (C) n-type conductor
• (D) none of these

Solution When arsenic is added as an impurity to silicon, the resulting material is n type semiconductor

27 >>When Ge crystal is doped with phosphorus atoms, it becomes ?

• (A) superconductor
• (B) insulators
• (C) p type
• (D) n type

Solution When Ge crystal is doped with phosphorus atoms, it becomes n type

28 >>The depletion layer in the p-n junction region is caused by ?

• (A) Drift of electrons
• (B) Diffusion of carriers
• (C) Migration of impurity ions
• (D) Drift of holes

Solution In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating regionwithin a conductive, doped semiconductor material where the mobile charge carriers have been diffused away

29 >>The potential barrier in the depletion layer is due to ?

• (A) ions
• (B) holes
• (C) electrons
• (D) forbidden gap

Solution The potential barrier in the depletion layer is due to ions

30 >>A p-n junction has a thickness of the order of ?

• (A) 1 mm
• (B) 10^-12 cm
• (C) 1 cm
• (D) 10^-6cm

Solution A p-n junction has a thickness of the order of 10-6cm

31 >>The conductivity of P – type semiconductor is due to ?

• (A) none of the above.
• (B) both electron and holes
• (C) electrons
• (D) holes

Solution The conductivity of P – type semiconductor is due to electrons

32 >>An N-type Ge is obtained on doping the Ge- crystal with ?

• (A) B
• (B) gold
• (C) p type
• (D) Al

Solution An N-type Ge is obtained on doping the Ge- crystal with p type

33 >>A P – type crystal is obtained by doping A) silicon with arsenic, B) silicon with aluminium, C) Ge with boron, D) Ge with phosphorus, Hence, say whether ?

• (A) (A and C) are correct
• (B) (B and D) are correct
• (C) (B and C) are correct
• (D) (A and D) are correct

Solution silicon with aluminium, Ge with boron form p type semiconductor

34 >>Majority current carriers in N – types are ?

• (A) positive ions
• (B) electrons
• (C) negative ions
• (D) holes

Solution Majority current carriers in N – types are electrons

35 >>A solid having uppermost energy – band partially filled with electrons is called ?

• (A) a semi – conductor
• (B) none of the above
• (C) a conductor
• (D) an insulator

Solution conductor is an object or type of material that allows the flow of an electrical current in one or more directions. A metal wire is a common electrical conductor. In metals such as copper or aluminium, the mobile charged particles are electrons.

36 >>The number of valence electrons in a good conductor is generally ?

• (A) 5
• (B) 4
• (C) 3 or less than 3
• (D) 6 or more than 6

Solution The number of valence electrons in a good conductor is generally 3 or less than 3

37 >>Electrons are forbidden in a band (in a crystal) called the ?

• (A) conduction band
• (B) forbidden band
• (C) one of the above
• (D) valance band

Solution Electrons are forbidden in a band (in a crystal) called the forbidden band

38 >>The behavior of Ge as a semi – conductor is due to the width of ?

• (A) conduction band being small and narrow
• (B) forbidden band being small and narrow
• (C) conduction band being large
• (D) forbidden band being large

Solution The behavior of Ge as a semi – conductor is due to the width of forbidden band being small and narrow

39 >>P-N junction can be used as ?

• (A) modulator
• (B) rectifier
• (C) amplifier
• (D) oscillator

Solution P-N junction can be used as rectifier

40 >>To provide the abundance of holes the impurity added should be ?

• (A) tetravalent
• (B) pentavalent
• (C) monovalent
• (D) trivalent

Solution To provide the abundance of holes the impurity added should be trivalent

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