Question

Write a short note on Helical motion.

Answer 1

It has previously been thought that the charged particle moves in a plane parallel to the magnetic field`vecB. `If such a particle has some component of velocity parallel to `vecB, (vecv_"//")` then it leads to helical motion.

Since a componen `vecv_"//"` is parellel to `vec B`,  the magnetic force `vecF_m`will be

`vecF_m = v_"//" xx vecB = v.B sin (0°) = 0`    ....(i)

Thus, `vecv_"//"` will be unaffected, and the partical will proceed in the direction of`vecB` 

At the same time, as previously indicated, the perpendicular component of velocity `vecv_⊥` causes circular motion. As a result, the particle moves parallel to the field `vecB` on a circular route parallel to `vecB`. As a result, the path becomes a helix, as seen in the figure above.