Answer
a. The top and bottom charges are positive, and the middle one is negative.
b. There are 2 points equally spaced on either side of the negative charge, on a horizontal line passing through that charge.
Work Step by Step
a. Electric field lines emerge from positive charges and end on negative charges.
b. From the diagram it is clear that there will be 2 points at the described locations where the field line density is lowest. At such a point, the y-components of the fields from the 2 positive charges cancel, and the negative charge’s electric field cancels the x-component of the net field from the 2 positive charges.
