The two pages discuss the electric field and surface force for two equal, separated point charges ($\mathbf{q}$). The first focuses on calculating the total electric field ($\mathbf{E}$) on the equidistant plane of symmetry ($x_3=0$). Due to symmetry and superposition, the axial components of the individual fields cancel, leaving a field that is purely radial and parallel to the surface, which is key to generating the force. The second and the third examine the resulting surface force on the electric field, revealing that for equal (repelling) charges the total surface force is attractive (pointing inward) and balances the Coulomb repulsion, while for opposite (attracting) charges the surface force is repulsive (pointing outward), with the magnitude of the surface force being equal to the Coulomb force in both cases.

Brief audio

Electric Field and Surface Force-L.mp4

Cue Columns

<aside> ❓

1. What is the total electric field on the plane equidistant from two equal charges separated by a distance?
2. How does the surface force on the field differ when the two charges are equal compared to opposite?
3. In which direction does the surface force on the field point for two equal charges? </aside>