I am making a project on 'Transistor as a switch' and I am not really sure how to connect the potentiometer.Main aim is to vary the voltage.
I connected the -ve end of the battery to one of the ends of the pot, +ve end of the battery to the other end of the pot,-ve of multimeter to -ve of battery, +ve of mutimeter to the middle point of the pot and I got a perfect reading.
But doing the same in the circuit but it did not work.

Have to connect the pot with Vbb in the given diagram

 

Why did you start this new thread when I answered it yesterday in your original thread, here:
http://forum.allaboutcircuits.com/showthread.php?t=76739

EDIT: In your original thread you said, "Rb = 680k+680k+120k resistors in parallel" which is a total of 88.7k, not 200k. Your 100k pot might not work well if RB is 200k because then the maximum base current will be too low.

 

Sorry for starting a new thread.I have attached new readings in my previous post.I had connected the transistor and pot wrongly.Please let me know if the readings are correct.
Thanks a lot for helping me out.