The generated emf is collected by the electrodes and is given to the external circuitry. If we assume constant magnetic field, the emf is directly proportional to velocity.
e α v
The pipe used must be non magnetic to allow the field to penetrate the fluid and usually is non conductive such as plastic or glass so that it doesn’t provide a short circuit path between positive and negative induced potential at the fluid surface.
electromagnetic flow meter is shown in above figure. It consist of a pair of insulating electrodes buried flush in opposites sides of non conducting, non magnetic pipe carrying liquid whose flow is to be measured. It is surrounded by electromagnet which produces magnetic field. The fluid passes through this pipe. As the fluid passes, an emf is produced which is proportional to the velocity of flow. According to the faraday’s law.
e = BLv
B = flux density in testla.
L = length of conductor.
E = emf generated.