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

Question

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 0.42 m/s and the diameter of the vessel is 6.8 mm. In a 0.92-T magnetic field what is the magnitude of the voltage that is measured with the electrodes in the drawing?

Explanation / Answer

Magnetic Force on charge q

F = qVBsin(theta)

here given values are

theta = 90 degrees

V = 0.42 m/s

B = 0.92 T

F = q*0.42*0.92*1 = 0.3864*q

and also we know that (E = electric field)

F = qE

qE = 0.3864*q

E = 0.3864 V/m

so magnitude of measured voltage

V = E/d = 0.3864/(6.8*10^(-3)) = 56.82 volt

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