Physical law made use in flow meter is:-
Velocity Flow Meters. Magnetic flow meters operate on Faraday'slaw of electromagnetic induction that states that a voltage is induced when a conductor moves through a magnetic field. The liquid serves as the conductor and the magnetic field is created by energized coils outside the flowtube.
Henrys law
Grahams law
Daltons law
Faraday'slaw
Anesthesia Machine