Question

What can be the cause of helical motion of charged partial?

Answer 1

The Motion is due to magnetic field !. The cause of motion of any charged particle is due to magnetic field

Answer 2

Helical motion of charged particle in external magnetic field . When an electron moves in uniform external magnetic field with velocity not perpendicular,I understood that the magnitude of the force is only due to perpendicular component of velocity and is perpendicular to both components of velocity