Electric charge is conserved in an isolated system and occurs in quantised amounts for ordinary isolated particles. Like charges repel and unlike charges attract.

For point charges in vacuum, Coulomb’s law gives force magnitude F = k|q₁q₂|/r². Direction and superposition must also be considered.

The formula assumes an appropriate point-charge or symmetric model; an arbitrary extended distribution needs further analysis.

Electric field is force per unit positive test charge; its direction is the force direction on a positive charge.

Electric potential is potential energy per unit charge and is scalar. A zero potential at a point does not automatically imply zero field.

For electrostatic work, potential difference relates energy change to charge; the reference chosen for potential does not alter physical field predictions.

In electrostatic equilibrium, the field within the material of an ideal conductor is zero and its surface is equipotential. This is a specific equilibrium statement.

Capacitance is C = Q/V for the stated conductor arrangement and potential difference; one farad is one coulomb per volt.

For an ideal capacitor, stored energy can be written ½CV². Geometry and dielectric conditions influence capacitance.