Question

A negatively charged particle is moving in a circular path in the clockwise direction in a uniform magnetic field, parallel to the plane of the page. Find out the direction in which magnetic field lines point?

• A. Out of the page
• B. Into the page
• C. To the left
• D. To the right
• E. In a clockwise pattern parallel to the plane of the page

Answer 1

Answer: (B)

Into the page

As particle is in circular path, therefore magnetic field will be perpendicular to velocity of particle. For circular motion centripetal force must be directed toward centre, here magnetic force is acting as centripetal force so the direction of force is toward center at any instant. Let the negative (current will be in opposite direction) particle is moving toward right (due to clockwise direction) at the top of circle, force will be vertically downward (toward center of circle) therefore by Fleming's left hand rule, magnetic field is into the page.