(i) As, per initial balance situation of meter bridge we find that R/X = l/100- l ----(i)
If R and X are doubled and then interchanged. Let new position of null point be at length l' from end A.
Thus, we have 2X/2R = l'/100 - l' ----(ii)
Multiplying Eqs. (i) and (ii), we get
1= l/100-l x l'/100-l'
===> l' = 100-l
(ii) If the galvanometer and the battery are interchanged, there is no effect on the position of balance point at all and balance point remains unchanged.