An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, then the magnetic field must have a component
A) along the -y-axis
B) along the +y-axis
C) along the -x-axis
D) along the -z-axis
E) along the +z-axis

Question

Quizplus · Accepted Answer

EThe direction of magnetic deflection of a charged particle, such as an electron, can be determined using the right-hand rule. According to this rule, if the thumb of the right hand points in the direction of the velocity of the electron (here, along the +x-axis) and the fingers point in the direction of the magnetic field, then the force (and thus the deflection) experienced by the electron will be in the direction of the palm's push (perpendicular to both the velocity and the magnetic field). Since the electron is deflected in the -y direction, the magnetic field must be perpendicular to both the +x and -y directions, which means it could only be along the +z or -z directions, making options D and E correct.

An Electron Moving Along the +X-Axis Enters a Magnetic Field