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The correct answer is (c) 63

To EXPLAIN I would say: The relation between flux density and permittivity is given by En1/EN2 = ε2/ ε1. Put En1 = 18, ε1 = 3.5 and ε2 = 1. We GET En2 = 18 X 3.5 = 63 units.

Right choice is (c) 10.4

Explanation: By Snell’s law, the relation between incident and reflected waves is given by, E1 SIN θ1 = E2 sin θ2. THUS 6 sin 60 = E2 sin 30. We GET E2 = 6 x 1.732 = 10.4 units.

The correct OPTION is (B) 6

Explanation: The relation between ELECTRIC field and permittivity is GIVEN by Dt1/Dt2 = ε1/ε2. Put Dt1 = 12, ε1 = 2 and ε2 =1, we get Dt2 = 12 x 1/ 2 = 6 units.

Correct choice is (B) 24

To explain: At the boundary of a conductor- free space INTERFACE, the flux DENSITY is EQUAL to the charge density. Thus D = ρv = 24 units.

Right OPTION is (C) 36π

The best I can EXPLAIN: It is the conductor-free space boundary. At the boundary, E = ρ/εo. Put ρ = 10^-9 and εo = 10^-9/36π. We GET E = 36π units.

Correct choice is (a) ∫ E.dl = 0

The BEST I can explain: A CONSERVATIVE field implies the WORK DONE in a closed path will be zero. This is GIVEN by ∫ E.dl = 0.

The correct OPTION is (d) 24.6

Easy explanation: The ELECTRIC field is GIVEN by E = V/L. To get V, put E = 12.3 and L = 2.Thus we get V = E x L = 12.3 x 2 = 24.6 units.

Correct option is (d) 1.2

For EXPLANATION I would say: The conduction current density is given by J = σE and the convection current density is J = ρe v. When both are EQUAL, ρe v = σE. To get E, put σ = 20, ρe = 2.4 and v = 10, E = 2.4 x 10/20 = 1.2 units.

The correct CHOICE is (B) 2.2

For explanation: The mobility is DEFINED as the drift velocity per unit electric FIELD. Thus μe = vd/E = 23/11 = 2.1 UNITS.

Correct answer is (c) 24

For EXPLANATION I WOULD say: The convection current density is given by J = ρe x v. To get ρe, put J = 120 and v = 5. ρe = 120/5 = 24 units.

Correct option is (B) 21t

Explanation: Using continuity EQUATION, the PROBLEM can be solved. Div(J) =

– dρ/dt. Div(J) = 20cos x + cos z. At origin, we get 20cos 0 + cos 0 = 21. To get ρ, on integrating the Div(J) with respect to t, the charge DENSITY will be 21t.

Right choice is (C) 7

Explanation: The current is defined as the rate of change of charge in a circuit ie, I = dq/dt. On differentiating the charge with respect to TIME, we GET 3 + 2t. At time t = 2s, I = 7A.

Correct answer is (c) 0.6, DIELECTRIC

For explanation I would say: The current DENSITY is the product of conductivity and electric field intensity. J = σE. To get σ, PUT J = 12 and E = 20. σ = 12/20 = 0.6. Since the conductivity is less than unity, the MATERIAL is a dielectric.

The correct option is (a) Absorption of electric energy by DIELECTRIC in an AC field

Best EXPLANATION: In the scenario of an AC field, the absorption of electrical energy by a dielectric material is called as dielectric loss. This will RESULT in dissipation of energy in the form of HEAT.

The correct ANSWER is (d) (-2/3)

EASIEST explanation: The AC DIELECTRIC CONSTANT is given by εr = ε` – jε“, where ε` is the real part of AC dielectric and ε“ is the imaginary part of AC dielectric. The loss tangent is given by tan δ = ε“/ε` = -2/3.

Correct choice is (C) ELECTRIC SUSCEPTIBILITY

Explanation: Curie-Weiss law is GIVEN by χe = εr -1. Thus it is used to CALCULATE the electric susceptibility of a material.

Correct option is (b) Dielectric breakdown

Explanation: Due to VARIOUS TREATMENTS performed on the dielectric, in ORDER to make it conduct, the dielectric reaches a state, where it LOSES its dielectric property and starts to conduct. This PHENOMENON is called as dielectric breakdown.

Correct CHOICE is (B) Ferroelectric

The EXPLANATION: Curie-Weiss law is given by χe = εr -1 = C/(T-θ), where C is the curie constant and θ is the characteristic TEMPERATURE which is usually a few degrees HIGHER than the curie temperature for ferromagnetic materials.

The correct ANSWER is (a) True

The EXPLANATION is: In IONIC crystals, the total polarisation is ELECTRONIC and ionic in nature. Thus, it implies that it contains more than one type of atom and no PERMANENT dipoles.

Correct answer is (B) Sum of all TYPES of polarisation

The EXPLANATION: The total polarisation of a material is given by the sum of ELECTRONIC, ionic, orientational and interfacial polarisation of the material.

The correct OPTION is (c) Silicon

Best explanation: Elemental solid dielectrics are the materials consisting of single TYPE of atoms. Such materials have neither IONS nor permanent dipoles and possess only ELECTRONIC polarisation. Its EXAMPLES are diamond, sulphur and germanium.

Correct answer is (c) 60

To EXPLAIN I would say: The polarisation vector is given by, P = ε0 X χe x E, where χe = 5 and ε0 = 12. On SUBSTITUTING, we get P = 1 x 5 x 12 = 60 units.

Right answer is (c) 36

The explanation: The energy stored per unit VOLUME in a DIELECTRIC MEDIUM is GIVEN by, W = 0.5 X PE = 0.5 X 9 X 8 = 36 units.

Correct OPTION is (B) RATIO of DIPOLE moment to electric field

Easy explanation: Polarizability is a constant that is defined as the ratio of elemental dipole moment to the electric field strength.

Correct OPTION is (a) 200

For explanation I WOULD say: POLARISATION vector P = N x p, where N = 100 and p = 2. On substituting we GET P = 200 units.

Correct answer is (C) Conductivity

The explanation is: In free SPACE, ε = ε0 and μ = μ0. The relative PERMITTIVITY and permeability will be unity. Since the free space will contain no CHARGES in it, the conductivity will be zero.

Right ANSWER is (B) tan 40

Easy EXPLANATION: The LOSS tangent is given by tan 2θn, where θn = 20. Thus the loss tangent will be tan 40.

Correct option is (b) 45 out of phase

To EXPLAIN: The electric and MAGNETIC FIELDS will be out of phase by 45 in good CONDUCTORS. This is because their intrinsic impedance is given by η = √(ωμ/σ) X (1+j). In polar form we get 45 out of phase.

Correct OPTION is (B) Lossless DIELECTRIC

Best explanation: If loss tangent is less, then σ /ε ω <<1. This IMPLIES the conductivity is very poor and the material should be a dielectric. Since it is specifically mentioned very less, assuming the conductivity to be zero, the dielectric will be lossless (ideal).

The correct answer is (c) Loss tangent

Easiest EXPLANATION: JC /JD is a standard ratio, which is REFERRED to as loss tangent given by σ /ε ω. The loss tangent is USED to determine if the material is a conductor or dielectric.

Correct option is (d) 4

The explanation: Jd = dD/dt = εdE/dt in TIME domain. For frequency domain, CONVERT using Fourier TRANSFORM, Jd = εjωE. The magnitude of

Jd = εωE = ε(2πf)E. On SUBSTITUTING, we get 4 ampere.

Right option is (b) 36

Best explanation: The mean free path is defined as the average DISTANCE travelled by an electron before COLLISION TAKES place. It is given by, d = v X τc, where v is the velocity and τc is the collision time. Thus d = 18 x 2 = 36m.

The correct option is (a) 25

For explanation I WOULD say: The CONDUCTION CURRENT density is given by, Jc = σE. To get CONDUCTIVITY, σ = J/E = 100/4 = 25 units.

Correct option is (b) ELECTRIC field

Easy explanation: SUPERCONDUCTING materials DEPENDS only on the applied MAGNETIC field, resultant magnetization at the temperature considered. It is independent of the applied electric field and the corresponding polarization.

Correct answer is (b) Negative

Explanation: Due to PERFECT DIAMAGNETISM in a superconductor, its MAGNETIC SUSCEPTIBILITY will be negative. This phenomenon is called Meissner effect.

Correct option is (b) 5

To explain I WOULD say: The electric SUSCEPTIBILITY is given by χe = εr – 1. For a susceptibility of 4, the dielectric constant will be 5. It has no UNIT.