Q. Assertion (A): The optical dielectric constant (i.e., εr at optical frequencies)of ionic dielectrics is less than static dielectric constant.

Reason (R): At optical frequencies, Pi = 0.

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Q. A piece of iron is placed in a magnetic field

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Q. Assertion (A): Magnetism can be explained by the theory of magnetic domains.

Reason (R): The existence of magnetic domains is evident from the Bitter powder patterns.

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Q. Ferromagnetic materials

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Q. In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µᵣ will

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Q. In molecules of ionic crystals, orientation polarization is zero.

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Q. Assertion (A): CO₂ has no resultant dipole moment but CO has a dipole moment.
Reason (R): The structure of CO₂ is O = C = O.

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Q. For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in intensity of optical illumination results in

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Q. A permeable substance is one

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Q. When subjected to alternating stresses, an insulating material is characterised by complex dielectric constant ∈'r - j∈"r . In such materials, the dielectric losses under alternating stress is proportional

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Q. In carbon resistor colour code, the third band is red. It indicates

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Q. Rochelle salt is a ferroelectric material.

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Q. Paramagnetic materials have permanent magnetic dipoles but interaction between neighbouring dipoles is negligible.

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Q. Assertion (A): If difference between static and optical dielectric constant is high, the mechanical compressiblity of that material is also high.
Reason (R): For soft ions, ionic polarization per unit field is higher than that of hard ions.

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

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Q. The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called

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Q. In metals, the average drift velocity of electron per unit field is called mobility.

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Q. Ferrites have

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Q. In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.

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Q. Assertion (A): Relaxation time and mean time between collisions are equal when scattering is isotropic.

Reason (R): Mean free path of an electron λ, velocity of electron v and mean time between collisions tc are related as λ = vTc.

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