Conservation of charge a) from first principles, derive an expression for the conservation of charge (also known as the continuity equation) for a medium with uniform conductivity and permittivity. b) derive an expression for the continuity equation for a medium with a nonuniform conductivity c) using gauss's law as applied to a medium with a nonuniform permittivity, and combining it with your result for b), derive a generalized expression known as the charge relaxation equation where t, = €) is the relaxation time. scanned w camscanner ics