(a) Find the electrostatic energy per unit volume at a point in the presence of an electrostatic potential V=5x+3z, where x and z are the Cartesian coordinates of the points. [2]
(b) Find the electrostatic energy per unit length of the following system consisting of two long co-axial conducting hollow cylinders of radii 5cm (R) and 7cm (R2), as shown below, placed in vacuum. The inner and outer cylinders carry a charge +A and -A per unit length respectively. [3]