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 0.50 m/s and the diameter of the vessel is 4.2 mm. In a 0.78-T magnetic field what is the magnitude of the voltage that is measured with the electrodes in the drawing?