Materials and Components – Section 4

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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