Effects of an electric charge on Casimir wormholes: changing the throat size

In this paper we continue the investigation of the connection between Casimir energy and the traversability of a wormhole. In addition to the negative energy density obtained by a Casimir device, we include the effect of an electromagnetic field generated by an electric charge. This combination defines an electrovacuum source which has an extra parameter related to the size of the throat. Even if the electromagnetic energy density is positive, the null energy condition is still violated. The main reason is that the electromagnetic field satisfies the property ρ =-p_r . As a consequence, the traversable wormhole throat can be changed as a function of the electric charge. This means that the throat is no longer Planckian and the traversability is slightly less in principle but slightly greater in practice.