An electron moving in the $+ y$ direction, at right angles to a magnetic field, experiences a magnetic force in the $- x$ direction. The direction of the magnetic field is in the
A) +y direction.
B) $+ z$ direction,
C) $+ x$ direction.
D) $- x$ direction.
E) $- z$ direction.

Question

Quizplus · Accepted Answer

The direction of the magnetic force on a moving charge is given by the right-hand rule, which states that if you point the fingers of your right hand in the direction of the velocity of the charge (in this case, the $+y$ direction) and curl them towards the direction of the magnetic field, your thumb will point in the direction of the force. Since the force is in the $-x$ direction, for an electron (which has a negative charge), the magnetic field must be in the $+z$ direction to satisfy this rule. This is because the force direction is reversed for negative charges like electrons compared to the direction predicted by the conventional right-hand rule.

An Electron Moving in The +y+ y+y Direction, at Right Angles to a Magnetic Field, Experiences a Angles

An Electron Moving in The $+ y$ Direction, at Right Angles to a Magnetic Field, Experiences a Angles