An electron traveling horizontally enters a region where a uniform magnetic field is directed into the plane of the paper as shown. Which one of the following phrases most accurately describes the motion of the electron once it has entered the field?

Question

Quizplus · Accepted Answer

When an electron enters a magnetic field, it experiences a force perpendicular to its velocity and the direction of the magnetic field. In this case, the force is directed upward, so the electron will move in a circular path in the counterclockwise direction. Since the force is perpendicular to both the velocity and the magnetic field direction, the circular motion will be in the plane of the paper. The fact that the motion is circular means that the electron moves in a curved path, ruling out choices D and E. The motion is also downward, not upward, ruling out choices A and B. Therefore, the correct answer is C, downward and circular.

An Electron Traveling Horizontally Enters a Region Where a Uniform