1057could you give the solution?
Akash Anand Take two things in your mind.
1)If no current is flowing through any resistance then that resistance has no use (no PD) and at null deflection only external battery will provide current.
2) Find the potential at the two points (across the middle battery) and the diff in potential will be equal to the EMF of battery.
That information is enough. Just give a try and you will get the answer.Akash Anand Did you able to solve this question or still confused??
1057actually i did the first question....but not getting the answer to the second one...and in the answer key second question's answer is given as 60cm and not 90cm.
Akash Anand As far as I think if first answer is correct then second has to be correct, because the only change is in internal resistance and that wont going to play any role again. 