The equivalence principle is a fundamental concept of the general relativity and it essentially express the equality between inertial and gravitational mass. The idealizations concerning the so-called “Einstein elevator” containing observers and test masses enable us to readily understand such a concept, however the scenario becomes more complex when there are electric charges involved because they emit radiation when accelerated. Hastily, we could claim that a resting charge in a gravitational field does not radiate, while another inside an accelerated elevator relatively to an inertial frame of reference does emit radiation, seemingly violating the equivalence principle. Such a problem has stirred up many discussions and we present here the analysis put forth by Fritz Rohrlich in the 1960s. The author shows that the electromagnetic field of an accelerated charge has radiative form for some frames of reference only, thereby such a phenomenon does not have an absolute nature. The approach is simple and it defines the spacetime curvature as being null in the domain, and therefore it does not in fact represent a solution for the apparent paradox (once it does not consider a real gravitational field); however, its results have a didactic interest once they are useful as a motivation for a more profound discussion and help us to understand that there is no incompatibility between the equivalence principle and electrical charges. Also, the discussion shown here may be used as a starting point for more recent and general works on the problem.
Keywords
General Relativity; Equivalence Principle; Electromagnetism; Accelerated Charges
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