WAEC - Physics (2009 - No. 35)
An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, Er. A test charge is placed at a point p, distance r from the surface of the sphere. Let Eo represent the permitivity of free space. The magnitude of the electric field intensity at P is given by the expression
\(\frac{Q}{4 \pi E_o E_r r^2}\)
\(\frac{Q}{4 \pi E_o E_r(R + r)^2}\)
\(\frac{Q}{4 \pi E_o E_r(R - r)^2}\)
\(\frac{Q}{4 \pi E_o E_rR^2}\)