In which direction does a magnetic force act on an electron that is moving in the positive x-direction in a magnetic field pointing in the positive z-direction?
 A) any direction in the xy-plane
 B) the negative y-direction
 c) the negative x-direction
 D) the positive y-direction
 a particle with charge q is at rest when a magnetic field is suddenly turned on. The field
 points in the z-direction. What is the direction of the net force acting on the charged particle?
 a) In the z-direction.
 b) There is no force on the particle.
 c) In the y direction
 d) In the x direction