In this diagram you can see the potential difference across the battery and resistor is the same as the pd created by the battery (the battery and resistor are representing a battery with internal resistance):


I know the route through the voltmeter is not actually a route, so I'm guessing here is no current? But why* is there no difference in the voltmeter reading, whether you put the voltmeter across the battery and resistor or just the battery?

The following diagram makes sense to me as some pd should be dropped over the internal resistance (the 680ohm resistor):


*(physically, when I put the numbers into the equations it make sense mathematically, but I don't understand the physics side)


Question: event horizons are untraversable by observers far from the collapse?
Answer: It's key to remember that the observer outside of the black hole will never see you fall into the black hole.  However, this observer can jump into the black hole himself, and see what happened to you.  Outside of the black hole, since he is unable to receive light signals from you, he may say that you have stopped at the event horizon.  But since he can go in and see you (assuming you haven't been crushed by the singularity yet), it is a matter of philosophy of whether the infalling observer actually fell in or if he 'froze' at the event horizon.

Analogy: If you are accelerating in a rocket, you don't have to believe that time on earth slowed to a stop corresponding to your Rindler horizon. If you wish, you can conclude no such thing. However, it is indisputable that no signals from earth past a certain time will reach you as long as you continue accelerating. But you can stop accelerating and then see what you missed. Similarly, you can 'stop accelerating away from the SC horizon' - i.e. fall into it - and then see all the history of infaller's you missed.

You should read the entry on the Usenet Physics FAQ:

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html