The Reissner-Nordström metric is the spherically symmetric metric tensor on a Lorentzian manifold for an
electrovacuum with mass 
and total charge 
.
Its static line element is
 |
where 
. For electric and magnetic charges,
. When 
, the two horizon radii are
 |
The exterior has 
,
and 
gives the Schwarzschild metric. The charged
Penrose inequality compares enclosing area with the outer radius in this model.
