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Materials and Components – Section 4

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Materials and Components – Section 4

1.  Assertion (A): Diamond and carborudum are both very hard materials.

Reason (R): Valence band can be extremely strong.
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

Answer: Option A

Explanation:

Valence bond results in hardness.
2.  The chemical properties of atoms are determined by all the electrons and their configuration.
A. True
B. False

Answer: Option B

Explanation:

Chemical properties are governed by valence electrons only.
3.  Nichrome is used for
A. overload line wires
B. heater coils
C. lamp filaments
D. all of the above

Answer: Option B

Explanation:

Because heater coil must be made of high resistivity material.
4.  If k is Boltzmann’s constant and T is absolute temp, then at room temp.
A. kT
0.025 eV
B. kT 0.5 eV
C. kT 1 eV
D. kT 100 eV

Answer: Option A
5.  If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of
A. 1
B. – 1
C. 0
D. + 3

Answer: Option A
6.  The dielectrics having only one kind of atoms are known as elemental dielectrics.
A. True
B. False

Answer: Option A
7.  For a core having a relative permeability μr, magnetic dipole moment per unit volume M and field strength H, the flux density B is
A. B = μr (H + M)
B. B = μ0 (H + M)
C. B = μ0μr (H + M)
D. B = μ0μr (H – M)

Answer: Option B
8.  The law that (where K is thermal conductivity, σ is electrical conductivity and T is absolute temperature) for all metals is equal to a universal constant is known as
A. Lorentz law
B. Wiedemann Franz law
C. Curie Weiss law
D. Kittel law

Answer: Option A
9.  In elemental dielectrics, the orientation and ionic polarization are absent.
A. True
B. False

Answer: Option A
10.  In which of the following semiconductor are holes majority carriers
A. intrinsic
B. extrinsic
C. p type
D. n type

Answer: Option C

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