Venturimeter is based on Bernoulli s theorem. It consists of a two truncated tubes connected by a pipe at narrow ends. The pipe connecting the two tubes is called throat as shown in figure.
The venturimeter tube is positioned horizontally and the liquid is made to enter in it at end A and after passing through throat BC, it leaves tube at end D. Let at A, the area of cross-section of tube be a1, pressure of liquid be P1 and velocity be v1 And at the throat, the area of cross-section of tube be a2 pressure of liquid be P2 and velocity be v2