A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current?
A) into the page
B) out of the page
C) downward
D) upward
E) The magnetic force is zero because the velocity is parallel to the current.

Question

A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current? 
A) into the page 
B) out of the page 
C) downward 
D) upward 
E) The magnetic force is zero because the velocity is parallel to the current.

Quizplus · Accepted Answer

The magnetic force on a negatively charged particle moving in a magnetic field is perpendicular to both its velocity and the direction of the magnetic field. The direction of the magnetic field due to the current in the wire can be found using the right-hand rule: curl the fingers of your right hand in the direction of the current (to the right) and the thumb points in the direction of the magnetic field (out of the page). Since the particle is negatively charged, the direction of the magnetic force on it is opposite to the direction of the force on a positively charged particle. Therefore, the magnetic force on the particle is directed upward, perpendicular to both its velocity to the right and the magnetic field out of the page.

A Negatively Charged Particle -Q Is Moving to the Right