The addition of electrons (which have a negative charge) to a positively-charged Black Hole would merely result in a gradual neutralization of the Black Hole's positive charge, while its total mass (and thus the area of its event horizon) would increase.
It has been established that a Black Hole can have only three different measurable (by an outside observer) properties: mass (measured by its gravitational field and size of event horizon); spin (measured by its oblateness); and electrical charge (which could be measured by bringing another charged body near it and measuring the repulsion / attraction).
But is there a limit to the amount of charge that a Black Hole could accumulate? Would the "internal pressure" that would build up if one were to continually add, say, only protons eventually elicit any unusual effect measurable by outside observers?
That's what I'd like to know.
Regards,
I’d like to know, too.
What I was alluding to in that thought experiment was that the electrical repulsive force in the positively charged black hole could be significant compared to the gravitational force. I would think that would enlarge the event horizon, at least for some outside positively charged particle that happened to stray nearby. Electrons would neutralize that black hole, but increase its mass relatively modestly, making me think that would tend to shrink the event horizon.
But I’m not a cosmologist. I think of “event horizon” as “point of no return”. Maybe that’s wrong, or maybe I’m missing something.
Example: California’s power grid.