The bi-criteria grouping of energy into potential energy (P.E) and kinetic energy (K.E) is expanded by P.E --> K.E paths that have resulted in various energy forms (specific manifestations of energy). Consequently, there exist: light energy, nuclear energy, heat energy, chemical energy, electrical energy, mechanical energy, etc. An energy conversion is the change from one energy form to another. Implicit in the orchestration of this change are the containership of P.E in matter and the forces and motions that establish the K.E paths. The energy forms listed above are frequent candidates for conversions because they have become very beneficial to humans.
The establishment of P.E --> K.E paths is the fundamental prerequisite for energy conversions. For example, the P.E --> K.E paths that manifests heat energy is the consistent motions of the atoms of substances. The faster the motions, the more heat energy is produced. Other examples of P.E --> K.E paths manifestations are the fission of the nucleus of atoms and the motions of charged atomic particles.
The energy and the P.E --> K.E paths are expressions of Pj Problems. Consequently, energy conversions are expressions of Pj Problems