Velocity Selector: a Beam of Electrons Is Accelerated Through a Potential

Multiple Choice

Velocity selector: A beam of electrons is accelerated through a potential difference of 10 kV before entering a region having uniform electric and magnetic fields that are perpendicular to each other and perpendicular to the direction in which the electron is moving. If the magnetic field in this region has a value of 0.010 T, what magnitude of the electric field is required if the particles are to be undeflected as they pass through the region?

A) 2.3 × 10³ V/m
B) 7.9 × 10³ V/m
C) 5.9 × 10⁵ V/m
D) 6.0 × 10⁵ V/m
E) 7.2 × 10⁶ V/m