Question

+Q ————•————-+Q
Find the charge for of the dot for
Which net force is zero on
all the
charges

Answer 1

Answer:

Neither net charge is zero nor is the case that charge is not present(atleast not necessarily). Electric Field is a vector quantity, think of it like force(for an analogy), you can have net force at a point zero, that doesn't mean sources of forces doesn't exist. It just that the vector sum of all the forces at the point is zero.

So you can have following 3 cases in which electric field at a point can be zero.

No nearby charges. No source of electric field hence 0 electric field.

Symmetric arrangement of charges around a point, with all charges having same sign. E.g,n number of charges placed around a circle, equidistant to each of their adjacent counterparts all in a same plane. E=0 at center.(here net charge is not zero)

You can have 2 +ve charges placed diagonally at the corner of a square, and 2 -ve charges placed at other diagonal, net charge is zero, and net electric field is also zero. But the point here is, even if you remove any 1 diagonal pair, you can still have net E=0, at the centre point.

P.S : For net electric potential to be zero you need to have equal no. Of +ve and -ve charges equidistant to the point of consideration.