People in and out of a bar

So, I am still in Alabama because of lack of electricity in Louisiana (although we got power back last night - YAY!). My wife convinced me to go out and hear this band since we are staying at my parents and they said they would watch the kids. In general, I am way too old and crotchety to go out - but it appears I had no choice. Overall, it was not too bad except for staying out too late. (the band was actually pretty good - I think they were called [Fly By Radio](http://www.fly-byradio.com/) and they played 80s musics) The one thing I thought about while in the bar was the long line of people waiting to go in. At some point, the number of people inside reaches its maximum capacity. People still come in because some people leave. Here is my rough sketch of this: (I call it a bar graph - get it?)


My first idea was to think of the bar as a capacitor and maybe this works. Ok, now I made something positive out of my trip.