## 1. Which one of the following current densities, $$\overrightarrow {\bf{J}} $$ can generate the magnetic vector potential $$\overrightarrow {\bf{A}} = \left( {{y^2}{\bf{\hat i}} + {x^2}{\bf{\hat j}}} \right)?$$

## 2. A metal has free-electron density n = 10^{29} m^{-3}. Which of the following wavelengths will excite plasma oscillations?

^{29}m

^{-3}. Which of the following wavelengths will excite plasma oscillations?

## 3. The electric field of a plane electromagnetic wave is $$\overrightarrow {\bf{E}} = \overrightarrow {{{\bf{E}}_0}} \exp \left[ {i\left( {{\bf{\hat x}}k\cos \alpha + {\bf{\hat y}}k\sin \alpha - \omega t} \right)} \right].$$ If $${\bf{\hat x}},\,{\bf{\hat y}}$$ and $${{\bf{\hat z}}}$$ are cartesian unit vectors, the wave vector $$\overrightarrow {\bf{k}} $$ of the electromagnetic wave is

## 4. The dispersion relation for a, low density plasma is ω^{2} = ω_{0}^{2} + c^{2} k^{2}, where ω_{0} is the plasma frequency and c is the speed of light in free space. The relationship between the group velocity (v_{g}) and phase velocity (v_{p}) is

^{2}= ω

_{0}

^{2}+ c

^{2}k

^{2}, where ω

_{0}is the plasma frequency and c is the speed of light in free space. The relationship between the group velocity (v

_{g}) and phase velocity (v

_{p}) is

## 5. Aspherical conductor of radius a is placed in a uniform electric field $$\overrightarrow {\bf{E}} = {E_0}\,{\bf{\hat k}}.$$ The potential at a point P(r, θ) for r > a, is given by $$\phi \left( {r,\,\theta } \right) = {\text{constant}} - {E_0}r\cos \theta + \frac{{{E_0}{a^3}}}{{{r^2}}}\cos \theta $$

where, r is the distance of P from the centre O of the sphere and θ is the angle, OP makes with the Z-axis.

The charge density on the sphere at θ = 30° is

where, r is the distance of P from the centre O of the sphere and θ is the angle, OP makes with the Z-axis.

The charge density on the sphere at θ = 30° is

## 6. A non-relativistic charged particle moves along the positive X-axis with a constant positive acceleration $$a{\bf{\hat x}}.$$ The particle is at the origin at t = 0. Radiation is observed at t = 0 at a distant point (0, d, 0) on the Y-axis. Which one of the following statements is correct?

## 7. In a non-conducting medium characterized by ε = ε_{0}, μ = μ_{0} and conductivity σ = 0, the electric field (in V/m) is given by $$\overrightarrow {\bf{E}} = 20\sin \left[ {{{10}^8}t - kz} \right]{\bf{\hat j}}.$$ The magnetic field $$\overrightarrow {\bf{H}} $$ (in A/m), is given by

_{0}, μ = μ

_{0}and conductivity σ = 0, the electric field (in V/m) is given by $$\overrightarrow {\bf{E}} = 20\sin \left[ {{{10}^8}t - kz} \right]{\bf{\hat j}}.$$ The magnetic field $$\overrightarrow {\bf{H}} $$ (in A/m), is given by

## 8. An electromagnetic wave with $$\overrightarrow {\bf{E}} \left( {z,\,t} \right) = {E_0}\cos \left( {\omega t - kz} \right){\bf{\hat i}}$$ is travelling in free space and crosses a disc of radius 2 m placed perpendicular to the Z-axis. If E_{0} = 60 V/m, the average power in watt, crossing the disc along the Z-direction is

_{0}= 60 V/m, the average power in watt, crossing the disc along the Z-direction is