Exercise: Materials And Components

Questions for: Materials And Components

If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature
A:
both will have equal value of resistivity
B:
both will have equal negative resistivity
C:
resistivity of germanium will be higher than that of silicon
D:
resistivity of silicon will be higher than that of germanium
Answer: D

Resistivity of silicon is more than that of germanium.

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In atomic physics, a state with l = 0 is called p state.
A:
True
B:
False
C:
D:
Answer: B

The state with l = 0 is called s state.

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Assertion (A): In imperfect capacitors, the current does not lead the applied ac voltage by 90°.

Reason (R): When subjected to ac fields, the dielectric constant can be expressed as ∈'r - j∈"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: A

Imaginary part of ∈r gives rise to absorption of energy by the material from alternating field.

Hence current does not lead the voltage by 90°.

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A parallel plate capacitor has its length, width and separation doubled. It fringing effects are neglected, to keep the capacitance same, the dielectric constant must be
A:
halved
B:
kept the same
C:
doubled
D:
made 4 times
Answer: A

. When dimensions are changed, A become four times and d becomes twice.

Since ∈0 is constant, ∈r must be halved to keep C constant.

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Material which lack permanent magnetic dipoles are known as
A:
paramagnetic
B:
diamagnetic
C:
ferromagnetic
D:
ferrimagnetic
Answer: B

Diamagnetic materials have no permanent magnetic diploes.

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