In medicine, it is often important to monitor the blood flow in certain areas of the body. However, the movement of blood is difficult to monitor directly. Instead, some medical devices use the Hall effect, taking advantage of the fact that the blood flowing through a vein contains a considerable number of freeions. Model the vein in a patient's arm to be of rectangular cross section, as shown in the figure, with a width?=4.00mm w = 4.00 mm and height?=2.95mm h = 2.95 mm . The entire section of the vein is immersed in a constant magnetic field of?=0.0755T, B = 0.0755 T, pointing horizontally and parallel to the width. A medical device constantly monitors the resulting Hallvoltage.

Suppose that medical precautions mandate that the speed of the blood flow for this particular component of the body should never drop below21.10cm/s. 21.10 cm / s. At what minimum Hall voltage?H, V H , in millivolts, should the medical device be designed to trigger an alarm to the medicalstaff?0

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