Materials and Components – Section 4(Page 4)

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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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