Q. Semi conducting materials are all

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Q. Silicon and germanium atoms combine orderly into array of atoms located in repetitive geometric pattern. This pattern is called

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Q. In a pure sample of silicon

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Q. Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus.

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Q. Assertion (A): ∈ᵣ can be determined experimentally by measuring the capacitance of a parallel plate capacitor with and without the dielectric.
Reason (R): Capacitance of a parallel plate capacitor = Ɛ₀ƐᵣA/d .

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Q. Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - (e/m) E.

Reason (R): If there are n electrons/m³ moving with velocity vᵪ and each electron has a charge - e, the current density J = - n evᵪ.

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Q. When a pentavalent impurity is added, the semiconductor becomes

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Q. In body centred cubic structure, comers and centre of the cube are occupied by identical atoms.

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Q. For a multiplate capacitor having n plates, A as area of each plate, the capacitance is proportional to

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Q. The orientation polarization is

1. directly proportional to temperature
2. inversely proportional to temperature
3. inversely proportional to square of permanent dipole moment
4. directly proportional to square of permanent dipole moment.

Which of the above are correct?

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Q. The relaxation time of electrons in a metal is of the order of

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Q. Assertion (A): For elemental dielectrics, P = NaeEi where N is number of atoms/m³, P is polarization, ae is electronic polarization and Ei is internal electric field.

Reason (R): In elemental dielectrics there are no permanent dipoles or ions.

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Q. The circumference of an electron orbit is equal to integer times the wavelength of electron.

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Q. In a specimen of silicon steel, a field strength of 200 A/m causes a flux density of 0.5 T. In a specimen of cast iron, the same H would cause B to be

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Q. In a rare gas, the molecules of some atoms have an excess positive or negative charge. The electric field tends to shift positive ions relative to negative ions. This is known as ionic polarization.

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Q. Thermistor is used in

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Q. Nichrome is used for

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Q. The electric dipole moment of a neutral system of point charges Q1, Q2.... is ∑Qiri . The charges Qi

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Q. The class of insulation of impregnated paper is

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Q. Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700°C.

Reason (R): The physical properties of a material are determined mostly by the extent of impurities.

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