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 x 10^3 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 1.68 x 10^-5 T, determine
the maximum possible potential difference (in V) between the two
ends of the tether.