The radiation emitted by a charged particle moving with arbitrary acceleration is considered. The field generated by such a particle, described by a potential having both spatial and temporal components, is investigated. To analyze the flow and production of energy, the law of change of momentum in a covariant form, previously obtained based on a covariant analysis of the variation of the electromagnetic field Lagrangian, is applied. It is shown that a charge moving with acceleration transfers energy to the field, which is then carried away by the field into the surrounding space. The presented approach can also be applied to the analysis of the law of change of momentum during the emission of gravitational waves.