Working- 

Electromagnetic flow meter works based on Faraday’s Law of Electromagnetic Induction. According to this principle,
"When any conductive material (fluid) passes through a magnetic field , a voltage is generated, this voltage is directly proportional to the velocity of the material (fluid) ".

Mathematically:-

 Magnetic flow meters works based on Faraday’s Law of Electromagnetic Induction. According to this principle, when a conductive medium passes through a magnetic field B, a voltage E is generated which is proportional to the velocity v of the medium, the density of the magnetic field and the length of the conductor. In a magnetic flow meter, a current is applied to wire coils mounted within or outside the meter body to generate a magnetic field. The liquid flowing through the pipe acts as the conductor and this induces a voltage which is proportional to the average flow velocity. This voltage is detected by sensing electrodes mounted in the Magflowmeter body and sent to a transmitter which calculates the volumetric flow rate based on the pipe dimensions.
 we can state Faraday’s law as-

E is proportional to V x B x L
[E is the voltage generated in a conductor, V is the velocity of the conductor, B is the magnetic field strength and L is the length of the conductor].