what will happen if we remove the red wire from the circuit i the first circuit? as it is not connected to any components.

bekathwia28 days ago

Nothing will happen. It is used in later lessons. It's standard practice to always connect power and ground at the same time, as described in the lesson:

"This is a common configuration you will use again and again, and should be your go-to setup for new breadboards, even if you aren't using both buses immediately. Circuits in this lesson will connect to the ground bus, and in the next lesson you'll use some components that will connect to the 5V power bus."