Answer:
The current is not used up. The electrons flow through the entire circuit and this travel is the current. They flow until they are not charged anymore. That is also why the circuit must be closed or else electrons would escape not just light it up for a second then go out.
Explanation:
It is 6 g/cm3 because density cannot be negative, and it is not speed in which the unit would be m/s.
It will sink because mass does not affect the physical properties of the object.
The sun?? It stays in one spot, but from our point of view, it travels around the earth...