[quote user="Niranjan Manoharan"]Connected it to the ground and it works. I'm yet to test it with a potentiometer..... Can you explain why this is happening ??, so the voltage on the pin is "high" without any connection ?[/quote]
Not necessarily. Consider it's just undefined, depends on pin input impedance, isolation quality, surrounding EMI or DC/static potential level. For example on high impedance input pin especially if it is connected to PCB trace, you easily can receive nearby switching PSU noise or other EMI, or just your VCC can leak into pin/trace through conducting dirt on PCB. Check datasheet for input pin leakage current of your chip and you will see that not much input current is needed for pin: 50 nA.
You shall _never_ ever leave input pins floating. It's one of the basic electronics rules. Well of course there are exceptions like touch sense.