4. Electric potential due to a point charge. The electric field due to a point charge of strength Q at the origin has a potential function K P = TQ where 2 =x2+y*+z2 is the square of the distance between a variable point P(x,y,z) and the charge. k>0 is a constant. The electric field is given by E=-Ve Where Vg is the gradient in three dimensions. a. Show that the three-dimensional electric field due to a point charge is given by Xy z E(x,y z) = kQ (rgrgr) r3 73 b. Show that the electric field at a point has a magnitude k 1] = X 2