'Flow measurement' by an electromagnetic (EM) flowmeter relies on:
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Pressure difference across an orifice
Faraday''s law: conductive fluid in magnetic field generates EMF ∝ velocity — no pressure drop, works with slurries
Counting bubbles in flow
Sonic pulses reflected by particles
Correct Answer
B. Faraday''s law: conductive fluid in magnetic field generates EMF ∝ velocity — no pressure drop, works with slurries
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EM flowmeter: Faraday''s law of induction — electrically conducting liquid flowing through magnetic field generates EMF proportional to velocity. E = B×D×V (E = EMF, B = magnetic flux, D = pipe diameter). Requires: electrically conductive fluid (water, sewage, slurry — minimum σ ~ 5 μS/cm). Not for: petroleum (non-conducting) — use Coriolis. Advantages: no moving parts, zero pressure drop, measures any direction, works with solids-laden flow.
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