Exercise: Materials And Components

Questions for: Materials And Components

Assertion (A): In many materials, dielectric polarization causes mechanical distortion.

Reason (R): If dielectric polarization causes mechanical distortion then mechanical distortion must cause dielectric polarization.

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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As the temperature of a pure silicon specimen is increased
A:
the number of free electrons increases
B:
the number of holes decreases
C:
the number of holes increases
D:
the number of free electrons and holes increases
Answer: D
No answer description is available. Let's discuss.
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Consider the following statement
If an electric field is applied to an n type semiconductor bar, the electrons and holes move in opposite directions due to their opposite charges. The net currents is
  1. both due to electrons and holes with electrons as majority carriers
  2. sum of hole and electron currents
  3. difference between electron and hole currents.
Which of above statements are correct?
A:
1 only
B:
1 and 2
C:
2 only
D:
3 only
Answer: B

The net current is sum of currents due to holes and electrons.

In n type materials, electrons are majority carriers.

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In a piezoelectric crystal, the application of mechanical force will cause
A:
plastic deformation of crystal
B:
magnetic dipoles in the crystal
C:
electrical polarization in the crystal
D:
shift in Fermi level
Answer: B

Piezoelectric materials permit conversion of mechanical force into electrical energy.

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When a material becomes a superconductor, its resistivity becomes
A:
very small
B:
zero
C:
about 10% of normal value
D:
about 20% of normal value
Answer: B

A superconductor has zero resistance.

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