Question

Capillary tubes of length `l` and `2l` are connected in series, their radii are r and `2r` respectively. If stream line flow is maintained and pressure difference across first and second capillary tubes are `P_(1)` and `P_(2)` respectively then find the ratio `(P_(1))/(P_(2))`.

Answer 1

Equating the rate of flow of liquid,
Here `Q_(1)=Q_(2)` and `Q=(pir^(4)P)/(8etal)`
`because(pi(r)^(4)P_(1))/(8etal)=(pi(2r)^(4)P_(2))/(8eta(2l))implies(P_(1))/(P_(2))=8`