A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the magnetic field must have a component
A) downward.
B) towards the west.
C) upward.
D) towards the east.
E) towards the north.

Question

Quizplus · Accepted Answer

The direction of the force on a moving charge in a magnetic field is given by the right-hand rule. Since the proton (a positively charged particle) curves downward while moving north, the magnetic field must be towards the east to create a force in the downward direction according to the right-hand rule.

A Proton, Moving North, Enters a Magnetic Field