  In Field theories with simple or semi-simple unitary, local or global
symmetries, the electric charge is related to a global one. This is the case
also in electroweak gauge theories even before the spontaneous symmetry
breaking (SSB), where these quantities are defined in order to expand the
Lagrangian respecting the conservation laws after the breaking. So, the
electric charge assignment within a given multiplet is done (in units of jej)
considering only global symmetries, even though in general, the electric charge
operator is a linear combination of the diagonal generators of the non-Abelian
symmetry plus some Abelian factor. In this work we show how this operator can
be systematically constructed from any representation in the Standard Model and
some of its extensions as the 3-3-1, left-right symmetric and grand unified
models.
