Materials and Components – Section 4(Page 4)

Materials and Components – Section 4

31.Lines of magnetic field cannot intersect.
A.True
B.False

Answer: Option A

32. Assertion (A): Dielectric losses are proportional to tan δ.

Reason (R): tan δ =

where ∈r and ∈r denote the real and imaginary parts of ∈r.
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

33. At T = 0, the resistivity of a perfect single crystal of a metal is
A.0
B.low
C.high
D.finite

Answer: Option A

Explanation:

At absolute zero temperature resistivity of metals is zero.

34. In a polyatomic gas, the types of polarization which exist together are
A.electronic and orientational
B.electronic and ionic
C.ionic and orientational
D.electronic, orientational and ionic

Answer: Option D

Explanation:

All the three types of polarization exist in polyatomic gases.

35.Assertion (A): Metals are better heat conductors than insulators.

Reason (R): If is temperature gradient, Q is heat flow density and K is thermal conductivity, then Q = – K (dT/dx).

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

36. The number of tightly bound electrons in silicon atom are
A.14
B.10
C.6
D.4

Answer: Option B

Explanation:

Silicon has 14 electons and 4 valence electrons. The 10 electrons in the inner orbits are tightly bound.

37. Electric dipole moment is usually expressed in debye units. Here, 1 debye unit equals
A.3.33 x 10-30 C-m
B.3.33 x 10-30 C-m2
C.3.30 x 10-10 C-m
D.3.33 x 10-10 C-m2

Answer: Option A

38. A particle of charge Q coulombs is bound elastically to an equilibrium position with a force constant of f newton per metre. The polarizability of the system is
A.
B.
C.
D.Qf

Answer: Option B

39. 1 Bohr magneton = .
A.True
B.False

Answer: Option A

40. An electron (charge –e) is rotating in a circular orbit of radius R, around a proton with charge +e at a constant angular velocity ω. The orbital magnetic dipole moment is
A.0.5 eω R2
B.eω R2
C.2 eω R2
D.0.5 eω R3

Answer: Option A

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