An electron, moving west, enters a magnetic field of a certain strength. Because of this field the electron curves upward. What is the direction of the magnetic field?
A) towards the north
B) towards the south
C) upward
D) downward
E) towards the west

Question

Quizplus · Accepted Answer

According to the right-hand rule, when a charged particle (such as an electron) moves in a magnetic field, the direction of the magnetic force acting on it is perpendicular to both the direction of its motion and the direction of the magnetic field. Since the electron moves westward and curves upward, the magnetic force must be directed northward (perpendicular to both west and up). Therefore, the direction of the magnetic field is towards the north.

An Electron, Moving West, Enters a Magnetic Field of a Certain