In the glory days of this forum by now you would have had several replies. Some would have ridiculed you and the rest would have told you about brushes and slip rings.
The tower has stationary insulated rings of brass, and the rotating part has hunks of carbon called brushes that rub against it to transfer the power to what moves. That's oversimplified, but you get the idea. Google commentator for more.
Your "slipknot" concept is interesting. I would have never thought of it.