Two positive point charges Q1 = 16 micro-coulombs and Q2 = 4 micro-coulombs are separated in a line by a distance of 3 meters. Find the spot on the line between the charges where the electric field is zero.

Explanation

We have to search for the null point where the resultant field is zero. Since the two point charges are of similar nature (both positive), there cannot be a null point on the line lying either left of point A or right of point B as in these regions the individual fields produced by the charges are parallel and hence cannot nullify each other. However there is a possibility of a null point between the points A and B. Let P be that point (lying at a distance x from point A).Therefore, the resultant electrostatic field is zero at a point (on the line joining the two charges) lying 2m right of the charge 16 μC or 1m left of the charge 4μC.