Exercise: Materials And Components

Questions for: Materials And Components

Electrical conductivity of metals expressed in ohm-1 m-1 is of the order of
A:
1010
B:
105
C:
10-4
D:
10-6
Answer: B

Conductivity is reciprocal of resistivity. Since resistivity of metals is around 10-7 ohm-m, conductivity is about 107 ohm-1 m-1. So 105 is the nearest value.

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For a given value (n) of principle quantum number, the number of possible electronic states are
A:
n
B:
n2
C:
n3
D:
n
Answer: B

The total number of states corresponding to a given value of n is equal to

(2l + 1) = 1 + 3 + .... + [2(n-1) + 1] = n2.

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Spontaneous polarization occurs in ferroelectric materials.
A:
True
B:
False
C:
D:
Answer: A
No answer description is available. Let's discuss.
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An electron in a homogeneous magnetic field and having velocity perpendicular to the direction of field moves
A:
perpendicular to the field
B:
along the field
C:
along a straight line inclined at 45° to field
D:
in a circular path
Answer: D
No answer description is available. Let's discuss.
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Assertion (A): In some materials, ∈r is independent of temperature while in others, ∈r depends on temperature.

Reason (R): If permanent dipoles are absent, ∈r varies with 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: C
No answer description is available. Let's discuss.
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