Materials and Components - Section 1 (6)

Directions to Solve

Materials and Components - Section 1

41.

Two materials having temperature coefficients of 0.004 and 0.0004 respectively are joined in series. The overall temperature coefficient is likely to be

A.	0.08
B.	0.04
C.	0.001
D.	0.0001

Answer: Option C

Explanation:

The overall temperature coefficient will be less than 0.004 and more than 0.0004.

42.

Assertion (A): Electronic and Ionic polarization in a polyatomic gas are independent of temperature.

Reason (R): The orientation polarization is independent of temperature.

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 C

Explanation:

Orientation polarization is inversely proportional to temperature.

43.

The minority carrier life time and diffusion constant in a semiconducting material are 100 μs and 100 cm2/s respectively. The diffusion length of carriers is

A.	0.1 cm
B.	0.01 cm
C.	0.0141 cm
D.	1 cm

Answer: Option A

Explanation:

Diffusion length = sqrt(Carrier life time x Diffusion constant) = (100 x 10-6 x 100)0.5 = 0.1 cm.

44.

The core of a coil has a length of 10 cm. The self inductance is 8 mH. If the core length is doubled, all other quantities remaining the same, the self inductance will be

A.	32 mH
B.	16 mH
C.	16 mH
D.	8 mH
E.	4 mH

Answer: Option D

Explanation:

Inductance is inversely proportional to the core length.

45.

The conductivity of intrinsic semiconductor is given by

A.	eni(μp - μn)
B.	eni(μp + μn)
C.	ni(μp + μn)
D.	ni(μpμn)

Answer: Option B

Explanation:

For intrinsic semiconductor,

Conductivity = (Electron charge) x (Number of charge carriers) x (Sum of mobilities of holes and electrons).

46.

Assertion (A): Atomic number of sodium is 11.

Reason (R): Sodium has a body centred cubic lattice.

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 B

Explanation:

Atomic number is not dependent on lattice structure.

47.

In paramagnetic materials

A.	permanent magnetic dipoles exist but the interaction between neighbouring dipoles is negligible
B.	permanent magnetic dipole do not exist
C.	permanent magnetic dipoles exist and the interaction between neighbouring dipoles is very strong
D.	permanent magnetic dipole moment may or may not exist

Answer: Option A

Explanation:

In paramagnetic materials interaction between neighbouring dipoles is negligible.

48.

Above ferroelectric curie temperature, spontaneous polarization in ferroelectric materials becomes stronger.

A.	True
B.	False

Answer: Option B

Explanation:

Spontaneous polarization vanishes above ferro-electric Curie temperature.

Materials and Components - Section 1 (6)

Materials and Components - Section 1

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