I have a question in my mind. What if I keep holding a Duracell(1.5V Battery) touching both the terminals with my fingertips? Will the circuit be completed and the battery drain? Or will it have no effect? Why?
You have to consider the electrical resistance of your fingers. This Aricle shows that the human body has a resistance of up to 100,000 ohms. Air has a resistance of about 2 x 10^16 ohms. While a very long thick wire has a resistance of 4 ohms. So, it looks like your fingers would indeed conduct electricity faster than air, but you'd have to hold the battery for a REALLY long time before you drain it.