Two electrons are placed; one at north pole and other at south pole of earth. Find the force between them. Given diameter of earth= 12800 km.

Answer 1

recall that the electric force

F = 9.0*10^9 (q1*q2)/r^2
So, plug in your values, remembering how many electrons are in a Coulomb, and you have only 1 electron at each pole. r must be in meters, of course, not km.

Answer 2

(1.8)10to the power -24