Key Idea : Search for the relations of electric potential and electric field at a particular point. At any point, electric potential due to charge Q is V=4πε01⋅rQ where r is the distance of observation point from the charge. At the same point, electric field is E=4πε01⋅r2Q Combining Eqs. (i) and (ii), we have E=Q4πε0V2=Q4πε0×(Q×1011)2=4πε0Q×1022 V/m