To accurately measure low viscosities of liquids, we describe how a Zimm–Crothers viscometer works and how to build it. The viscometer involves the action of a rotating magnetic field on a metallic cylinder floating on the liquid to be studied. The principles of electromagnetism and fluid mechanics involved make the viscometer an excellent tool for undergraduate laboratory courses and for measuring the shear viscosity of low viscous fluids. We discuss the advantages and limitations of this inexpensive and easy to use apparatus compared to other classical techniques. Calibrations with Newtonian fluids are explained and experiments with Non-Newtonian materials are discussed.
REFERENCES
Note that Foucault’s currents are generated inside the whole aluminum ring only if the penetration length of the electromagnetic field is larger than , the radius of the metallic ring. For aluminum we obtain at 100 Hz.
