An Electromagnetic Flowmeter Is Useful When It Is Desirable Not $v$

An electromagnetic flowmeter is useful when it is desirable not to interrupt the system in which the fluid is flowing (such as the blood in an artery during heart surgery) . Such a device is illustrated in the figure. The conducting fluid moves with speed $v$ in a tube of diameter $d$ . Perpendicular to this tube is a magnetic field B. A voltage $V$ is induced between opposite sides of the tube due to the motion of the conducting fluid in the magnetic field. For a certain case, $B =$ $0.120 \mathrm {~T} , d = 1.2 \mathrm {~cm}$ , and the measured voltage is $V = 2.88 \mathrm { mV }$ . Determine the speed of the fluid.

A) $11 \mathrm {~m} / \mathrm { s }$
B) $750 \mathrm {~m} / \mathrm { s }$
C) $0.075 \mathrm {~m} / \mathrm { s }$
D) $1.1 \mathrm {~m} / \mathrm { s }$
E) $2.0 \mathrm {~m} / \mathrm { s }$