Final answer:
The internal float device that is connected to the fill valve is called the ballcock.
Step-by-step explanation:
The internal float device that is connected to the fill valve is called the ballcock. It is commonly used in toilet cisterns to control the water level.
When the water level drops, the ballcock falls and opens the fill valve, allowing water to enter the cistern until the desired level is reached.
Once the water level is high enough, the ballcock rises and closes the fill valve.