If the wheat stone bridge depend on p.d. or volt across the ends then why there is a rule that r1×r3=r2 ×r4 then only no current will flow

Dear student,

We actually derive the condictionfrom the zero potential drop condition. We first assert that since no current flows in the resistor, the potential difference across its end must be zero. Then we write potential across the two points in terms of curerrents in the branches and the given resitors. In the end we get the above condition.

Hope it helps.