Question

A charge particle moving in magnetic field B, has the components of velocity along B as well as perpendicular to B. The path of the charge particle will be 

(1) helical path with the axis perpendicular to the direction of magnetic field B 

(2) straight along the direction of magnetic field B 

(3) helical path with the axis along magnetic field B 

(4) circular path

Answer 1

(3) helical path with the axis along magnetic field B 

Due to component V₁, 

magnetic force F = qv₁Bsinθ = 0

So v₁ remains unchanged but due to component v₂ magnetic force act towards centre i.e. moving it circular. So path is helical with the axis parallel to magnetic field B.