Where does electrostatic energy live? Classical physics’ answer is as elegant as it is revolutionary: it is not on the charges, but in the space where the field exists. Wherever there is a field , there is an energy density per unit volume. Integrating over all space recovers the total energy of the system, in perfect agreement with the count “on the charges”.
This section develops the idea starting from the parallel-plate capacitor case, generalises it to any distribution, and tests it on different geometries — the charged sphere, the cylindrical capacitor and the spherical one — showing how powerful it is to think of energy as a local property of the field.
- Electric energy density — , general validity, field energy of a charged sphere.
- Cylindrical and spherical capacitor — capacitance of coaxial and concentric geometries, coaxial cables.