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Materials and Components

1.

In molecules of ionic crystals, orientation polarization is zero.

Answer: A

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2.

Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.

Reason (R): Thermionic emission current ∝ T2 e-Ew/kT.

Answer: A

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3.

Assertion (A): At a temperature of 1000 K, thermionic emission current is about 0.1 A/cm2 of surface.

Reason (R): Thermionic emission current is given by Ith = SA0 Te-Ew/kT.

Answer: A

If different values are substituted in the equation for Ith the value of emission current comes out to be about 0.1 A/cm2.

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4.

Assertion (A): CO2 has no resultant dipole moment but CO has a dipole moment.

Reason (R): The structure of CO2 is O = C = O.

Answer: A

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5.

The colour code on a carbon resistor is green-blue-yellow. The tolerance is

Answer: C

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Answer: A

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Answer: D

Resistivity of silicon is more than that of germanium.

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8.

In crystalline solids, atoms are stacked in a regular manner.

Answer: A

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9.

The minority carrier life time and diffusion constant in a semiconducting material are 100 μs and 100 cm2/s respectively. The diffusion length of carriers is

Answer: B

Diffusion length = sqrt(Carrier life time x Diffusion constant) = (100 x 10-6 x 100)0.5 = 0.1 cm.

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10.

Which solid dielectric has highest temperature limit?

Answer: C

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