Plz tell me ans to this H.C.verma question?

Question

Assume that the magnetic field is uniform in a cubical region and is zero outside.Can you project a charged particle from outside into field so that the particle describes a complete circle in the field ?

Answer 1

no i don think so

this is not possible 4 any charged particle untill and unless external force is applied or the field is non uniform

4 charged particle and uniform field only a semicircular curve can be traced

Answer 2

For the particle to perform circular motion the particle must enter in the plane perpendicular to the magnetic field. If the particle enters at any angle(>0) with the face and we try to draw a complete circle, one part of circle surely lies outside the cube. So for complete circle to be inside, particle must enter parallel to the face which is not possible. answer of the question is "NO".  

Answer 3

look my dear.i am happy that u study good book.may god bless u and help u in achieving ur goal in ur life.

answer ;  when u project a particle pendicular to magnetic field , charged particle will experience a force in a plane perpendicular to the plane containing F and particle velocity V. then it will experince no force at all.so u can not make it finish a circle .,how hard u try.

particle will enter through one side of the cube and leave the other with no change in its magnitude of velocity and only change in the direction by 90.

hope u have got the answer