Two charges 2 mC and –2 mC are placed at points A and B 6 cm apart.
Identify an equipotential surface of the system.
The equipotential surface of this system is a plane perpendicular to the line joining the two charges, passing through its midpoint. At every point on this plane, the distances from both charges are equal. Since the charges are equal in magnitude (2 mC) but opposite in sign, their potentials cancel each other out, resulting in zero potential throughout this surface.
What is the direction of the electric field at every point on this surface?
The direction of the electric field at every point on this equipotential surface is perpendicular to the surface. Since the surface is a plane perpendicular to line AB, the electric field is directed along the line AB, from the positive charge (+2 mC at point A) toward the negative charge (–2 mC at point B).
Explanation
This question tests understanding of equipotential surfaces in an electric dipole system. For two equal and opposite charges, the perpendicular bisector plane is an equipotential surface with zero potential because potentials due to both charges cancel at equidistant points. The electric field is always perpendicular to equipotential surfaces, and for a dipole configuration, it points from the positive to the negative charge along the axial line.