Question

A negatively charged particle is moving through a magnetic field as pictured below. What is the direction off the force on the particle due to the magnetic field at the instant in the picture?

• A. north
• B. west
• C. east
• D. up
• E. down

Answer 1

The correct option is E down

When a charge q is moving with velocity v in the magnetic field B , the magnetic force is $\overrightarrow{F}=q(\overrightarrow{v}\times \overrightarrow{B})$

Thus, force is perpendicular to velocity and magnetic field. So it is normal to the plane of paper. Since the charge is negative so the direction of force will down to the plane of paper.