In an experiment designed to measure the earth's magnetic field using the hall effect, a copper bar 0.550 cm thick is positioned along an east–west direction. assume n = 8.46 × 1028 electrons/m3 and the plane of the bar is rotated to be perpendicular to the direction of b. if a current of 8.00 a in the conductor results in a hall voltage of 4.50 10-12 v, what is the magnitude of the earth's magnetic field at this location?