Why magnetic flowmeters avoid hydrocarbons: Magnetic (electromagnetic) flowmeters are generally not used for measuring hydrocarbon flow/velocity because hydrocarbons typically have which limiting property?

Introduction / Context:
Electromagnetic flowmeters employ Faraday’s law: a conductive fluid moving through a magnetic field induces a voltage proportional to velocity. They are popular for slurries and conductive liquids, but they require a minimum electrical conductivity to function. Hydrocarbons, being non-aqueous and largely non-ionic, fall well below that threshold.

Given Data / Assumptions:

• Standard magmeter with typical conductivity requirement (often > 1–5 μS/cm).
• Measured fluid class: petroleum hydrocarbons (gasoline, diesel, kerosene, crude).
• No special electrodes or injected conductivity enhancers are used.

Concept / Approach:
For magmeters, induced EMF E = k * B * L * v * σ_effective, where σ (conductivity) must be high enough to produce a measurable signal. Hydrocarbons have extremely low σ (near insulating), so the induced voltage is negligible relative to noise, rendering measurements unreliable. Their viscosity, flash point, or thermal conductivity are unrelated to the sensing principle and do not preclude other meter technologies (turbine, PD, Coriolis, ultrasonic clamp-on, etc.).

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer selection charts explicitly exclude low-conductivity fluids like oils and fuels from standard electromagnetic flowmeter applications.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing conductivity prerequisites with other physical properties; only conductivity is decisive for magmeter feasibility.

Final Answer:
Low electrical conductivity