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uestion I The drawing shows a type of flow meter that can be used to measure the

ID: 1771259 • Letter: U

Question

uestion I The drawing shows a type of flow meter that can be used to measure the speed of blood in situations when a blood vessel is sufficiently exposed (e.g., during surgery). Blood is conductive enough that it can be treated as a moving conductor. When it flows perpendicularly with respect to a magnetic field, as in the drawing, electrodes can be used to measure the small voltage that develops across the vessel. Suppose the speed of the blood is 0.27 m/s and the diameter of the vessel is 8.1 mm. In a 0.65-T magnetic field what is the magnitude of the voltage that is measured with the electrodes in the drawing? Electrode Blood Electrode Number Units the tolerance is +/-296

Explanation / Answer

The magnetic force on a charge q will be:
F = qvB = q*0.27*0.65 = q*0.1755, so it corresponds to an electric field of 0.1755.

The corresponding voltage is thus:
0.1755* 8.1e-3 = 1.42155*10^-3 = 1.42155 mV