A magnetic field ` vec(B) = B_(0)hat(j)` , exists in the region `a ltxlt2a` , and `vec(B) = -B_(0) hat(j)` , in the region `2a lt xlt 3a`, where `B_(0)` is a positive constant . A positive point charge moving with a velocity `vec(v) = v_(0) hat (i)` , where `v_(0)` is a positive constant , enters the magnetic field at `x= a` . The trajectory of the charge in this region can be like

Options

A.
B.
C.
D.

Answer

A

Explanation

Magnitic field in the region `a lt x lt 2a` will turn the particle towards positive `Z`-axis while the magnetic field in the region `2a lt x lt 3a` will exert force in opposite direction.The turning is smooth because the magnetic force is NOT impulsive.