From a homogeneous and isotropic dielectric material of dielectric constant ?r,

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Question
From a homogeneous and isotropic dielectric material of dielectric constant ?_r, a small volume element is taken out creating a cavity. The field can be kept homogeneous if D_i. (i.e., electric flux density inside the cavity) and D₀ (i.e., electric flux density outside the cavity) are such that
Options
A. D₀ = D_i
B.
C.
D. either (a) or (b)

Correct Answer

Explanation

Since the field is homogeneous

From a homogeneous and isotropic dielectric material of dielectric constant ?r, a small volume eleme

.

Materials and Components problems

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2. The chemical properties of atoms are determined by all the electrons and their configuration.
Options
A. True
B. False

3. The law that (where K is thermal conductivity, ? is electrical conductivity and T is absolute temperature) for all metals is equal to a universal constant is known as
Options
A. Lorentz law
B. Wiedemann Franz law
C. Curie Weiss law
D. Kittel law

5. In a ferromagnetic material, the internal field seen by a dipole is
Options
A. equal to applied field
B. equal to applied field minus a contribution from neighbouring dipoles
C. equal to applied field plus a contribution from neighbouring dipoles
D. equal to or less than applied field

6. At T = 0, the resistivity of a perfect single crystal of a metal is
Options
A. 0
B. low
C. high
D. finite

7. The iron core of a coil is removed so that it becomes an air cored coil. Its inductance will
Options
A. increase
B. decrease
C. remain the same
D. may increase or decrease

8. In a metal the probability of a state 0.1 eV below Fermi level being occupied
Options
A. is more than the probability of state 0.1 eV above Fermi level being occupied
B. is the same as the probability of state 0.1 eV above Fermi level being occupied
C. is less than the probability of state 0.1 eV above Fermi level being occupied
D. may be equal to or more or less than the probability of state 0.1 eV above Fermi level being occupied

10. Electrical conductivity of metals expressed in ohm^-1 m^-1 is of the order of
Options
A. 10¹⁰
B. 10⁵
C. 10^-4
D. 10^-6

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