Answer to Question #141047 in Electricity and Magnetism for Muhamnad Ali

Question

Two point charges of unknown magnitude and sign are placed
a distance d apart. (a) If it is possible to have E= 0 at any
point not between the charges but on the line joining them,
what are the necessary conditions and where is the point located(b) Is it possible, for any arrangement of two points charges, to find two points (neither at infinity) at which E=0 if so under what conditions?

Answer 1

Net electric field intensity E due to fields of two charges of intensities is zero only when the electric field intensities cancel each other out due to same magnitudes and opposite directions there. That point is called neutral zone.

When there are like charges(having same sign of charges),they “cancel” each other’s field at a point between them.Why? because their fields become equal and oppositely directed at that particular point.That becomes a sort of equipotential surface where there is no potential difference.

Or if the concerned charges are with same sign and equal magnitude,the zero field spot would exist in the exact middle of the separating distance of charges.

The concerned charges are with the same sign.

Zero field spot can exist in middle of the separating distance (if the concerned charges are with same magnitude) or nearer to the weak charge (in case of unequal magnitude)