Two small solid metal spheres A and B have equal radii and are in a vacuum. Their centres are 
apart. Sphere A has charge 
and sphere B has charge 
. The arrangement is illustrated in the figure below.
Point P lies on the line joining the centres of the spheres and is a distance of 
from the centre of sphere A.
Suggest why the electric field strength in both spheres is zero.
Show that the electric field strength is zero at point P. Explain your working.
