7.1. When an electron moves horizontally into a magnetic field that lies perpendicular to its motion, it experiences a magnetic force that acts in a direction perpendicular to both its motion and to the magnetic field. This causes the electron to move in a circular path around the axis of the magnetic field. The direction of the circular motion is perpendicular to both the direction of motion of the electron and to the direction of the magnetic field.
7.2. The force exerted on the electron can be calculated using the formula:
F = Bqv
where F is the force, B is the magnetic field strength, q is the charge of the electron, and v is the velocity of the electron.
Substituting the values in the given problem, we get:
F = (0.5T) x (-1.6 x 10^-19C) x (200m.s^-1)
F = -1.6 x 10^-17N
The negative sign indicates that the direction of the force is perpendicular to both the direction of motion of the electron and to the direction of the magnetic field, as explained in part 7.1.