A long conducting cylinder having a radius b is placed along the z-axis. The current density is $$\overrightarrow J = {J_a}{r^3}\widehat z$$ for the region r < b where r is the distance in the radial direction. The magnetic field intensity ($$\overrightarrow H $$) for the region inside the conductor (i.e., for r < b) is

If the magnetic field intensity ($$\overrightarrow H $$) in a conducting region is given by the expression, $$\overrightarrow H = {x^2}\widehat i + {x^2}{y^2}\widehat j + {x^2}{y^2}{z^2}\widehat k$$ A/m. The magnitude of the current density, in A/m², at x = 1 m, y = 2 m and z = 1 m is

As shown in the figure below, to concentric conducting spherical shells, centred at r = 0 and having radii r = c and r = d are maintained at potentials such that the potential V(r) at r = c is V₁ and V(r) at r = d is V₂. Assume that V(r) depends only on r, where r is the radial distance. The expression for V(r) in the region between r = c and r = d is

Consider a 3 $$\times$$ 3 matrix A whose (i, j)-th element, a_i,j = (i $$-$$ j)³. Then the matrix A will be