An isolated uniform conducting sphere has mass 
and charge 
. The gravitational field strength at the surface of the sphere is 
. The electric field strength at the surface of the sphere is 
.
Show that
where 
is a constant.
Show that the numerical value of is 
.
Assume that the Earth is a uniform conducting sphere of mass 
. The surface of the Earth carries a charge of 
that is evenly distributed.
Use the information in (a) to determine the electric field strength at the surface of the Earth. Give a unit with your answer.
State how the direction of the electric field at the surface of the Earth compares with the direction of the gravitational field.
.
