The electron is accelerated via a potential difference of 2.2 kV and directed into a region among the two parallel plates separated by 20 mm with a potential difference of 200 V between them. The electron is moving perpendicular to electric field of the plates when it enters the region among the plates. Determine what magnetic field is needed perpendicular to both the electron path and the electric field so that the electron travels in the straight line?

A horizontal conductor which is part of a power line carries a current of 7400 A from south to north. The magnetic field of earth (60.0 µT) is directed toward the north and is inclined downward at 70° to the horizontal. Determine the magnitude and direction of the magnetic force on 150 m of the conductor due to the Earth's field.