  The Penrose-Gibbons inequality for charged black holes is proved in spherical
symmetry, assuming that outside the black hole there are no current sources,
meaning that the charge e is constant, with the remaining fields satisfying the
dominant energy condition. Specifically, for any achronal hypersurface which is
asymptotically flat at spatial or null infinity and has an outermost marginal
surface of areal radius r, the asymptotic mass m satisfies 2m >= r + e^2/r.
Replacing m by a local energy, the inequality holds locally outside the black
hole. A recent definition of dynamic surface gravity k also satisfies
inequalities 2k <= 1/r - e^2/r^3 and m >= r^2 k + e^2/r. All these inequalities
are sharp in the sense that equality is attained for the Reissner-Nordstrom
black hole.
