An isolated solid metal sphere is positively charged. The variation of the potential 
with distance 
from the centre of the sphere is shown in the graph below.
Use the graph above to suggest
why the radius of the sphere cannot be greater than 
,
that the charge on the sphere behaves as if it were a point charge.
Assuming that the charge on the sphere does behave as a point charge, use data from the graph above to determine the charge on the sphere.
.
