A heart surgeon monitors the flow rate of blood through an artery using an electromagnetic flow meter (Fig. P29.71). Electrodes A and B make contact with the outer surface of the blood vessel, which has interior diameter3.00 mm. (a) For a magnetic field magnitude of 0.040 0 T, an emf of 160 μV appears between the electrodes. Calculate the speed of the blood. (b) Verify that electrode A is positive, as shown. Does the sign of the emf depend on whether the mobile ions in the blood are predominantly positively or negatively charged?

A heart surgeon monitors the flow rate of blood through an artery using an electromagnetic flow meter (Fig. P29.71). Electrodes A and B make contact with the outer surface of the blood vessel, which has interior diameter3.00 mm. (a) For a magnetic field magnitude of 0.040 0 T, an emf of 160 μV appears between the electrodes. Calculate the speed of the blood. (b) Verify that electrode A is positive, as shown. Does the sign of the emf depend on whether the mobile ions in the blood are predominantly positively or negatively charged?

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