In one of nasa's space tether experiments, a 20.0 km-long conducting wire was deployed by the space shuttle as it orbited at 7.86 ✕ 103 m/s around earth and across earth's magnetic field lines. the resulting motional emf was used as a power source. if the component of earth's magnetic field perpendicular to the tether was 1.38 ✕ 10−5 t, determine the maximum possible potential difference (in v) between the two ends of the tether.