A 5.0-nC charge is at (0, 0) and a -2.0-nC charge is at (3.0 m, 0). If the potential is taken to be zero at infinity, what is the work required to bring a 1.0-nC charge from infinity to point (0, 4.0 m)?

Three reasons for adding a dielectric material between the plates of a capacitor.
1. Dielectrics do not break down (allowing electric charge to flow"as readily as air, so a higher voltage can be applied without charge passing across the gap.
2. A dielectric allows the plates to be placed closer together without touching thus allowing an increased capacitance because the plate separation is less.
3. If a dielectric fills the space between the two conductors, it increases the capacitance.