A positively charged particle has a velocity in the negative z direction at point P. The magnetic force on the particle at this point is in the negative y direction. Which one of the following statements about the magnetic field at point P can be determined from this data? A. Bx is positive.
B. Bz­ is positive.
C. By is negative.
D. By is positive.
E. Bx is negative.

When reviewing the correct answer is A

Explanation:

The magnetic force is given by the expression

           F = qv xB

where the bold letters indicate vectors, from this expression the module can be calculated

          F = = q v b sin θ

the direction of the force is given by the rule of the right hand, for a positive charge the speed held by the thumb, the extended fingers point in the direction of the magnetic field and the palm points the direction of the force

in this case

the speed is in the negative part of the z axis

the force is in the negative direction of the axis and

consequently the magnetizing field is in the positive direction of the x axis

When reviewing the correct answer is A