The arduino does not know if something is connected to the analog input pin or not. So you get a conversion of whatever the voltage is on the pin.
With nothing connected to the pin, the pin is "floating" and may drift higher or lower.
The arduino does not know if something is connected to the analog input pin or not. So you get a conversion of whatever the voltage is on the pin.
With nothing connected to the pin, the pin is "floating" and may drift higher or lower.