Equation of an equipotential line in an electric field is y=2x , then the electric field strength vector at(1,2) may be ------ 1.4î+3j^ 2.4î+8j. 3. 8î+4j. 4.-8î+4j

Electric field line are always perpendicular to equipotential surface. So find perpendicular to i^ +2j^. Which is option (4.) -8i + 4j.Hope it clears. If u have doubts then please clearify. And if u like my answer then please approve answer