Find the electricity field intensity at any point due to point charge in terms of position vector .

Electricity field intensity is a vector with the direction outwards for a +ve charge and inwards for a -ve charge and magnitude :

E = k * q / r².

where,

k = constant of proportionality ( approx. used for cal. 9 * 10⁹ Nm²c-2 for air)

q = charge of the point charge

r = distance or magnitude of the position vector with the point charge at origin.

The direction of E is same as that of position vector in case of +ve charge and opposite of postion vector in case of -ve charge.