Measuring blood flow speed with magnetic field · CAP 2004 #Q22

Physics · electromagnetism

Problem

In order to measure the speed

v

of blood flow through an artery, a uniform magnetic field

B

is applied in a direction perpendicular to the flow and a voltmeter measures the voltage across the diameter

D

of the artery, at right angles to

B

. If positive and negative ions in the blood are longitudinally at rest with respect to the flow, the speed of the flow is closest to (a)

v = V/(BD)

; (b)

v = BD/V

; (c)

v = VD/B

; (d)

v = B/(VD)