In a meter bridge, the wire of length 1 m has a non- uniform cross - section such that , the variation `(dR)/(dl)` of its resistance R with length l is `(dR)/(dl) prop (1)/(sqrt(l))` ,Two equal resistances are connected as shown in the figure , the galvanometer has zero deflection when the jockey is at point P, what is the length Ap?

Options

A. 0.25m
B. 0.2m
C. 0.3m
D. 0.35m

Explanation

`(dr)/(dl)=k 1/sqrt1 , int dR =k int (dl)/sqrtl implies int_0^j k (dl)/sqrtl=int_l ^1 k (dl)/l`
`implies 2sqrtl=2-2sqrt1 implies 4sqrtI=2 implies 1=1/4 =0.25m`