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cat1995
cat1995
Student

A particle with the specific load q/m, enters into a magnetic field B. How much time does it need for describing a spire of helix.

The entrance of the particle into the magnetic field is made under an angle.

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Posted by cat1995 on Friday June 26, 2009 at 4:53 AM and tagged with magnetic field, particle, physic, specific load.

Answers:

  1. giorgiana1976
    giorgiana1976 Teacher
    Doctorate

    eNotes Editor

    Best answer as selected by question asker.

    The particle is actioned by the magnetic Lorentz' force:

    F=q*vxB, F=qvBsin alfa

    If we decompose the speed into 2 components, one is parallel with B and the other one is perpendicular, then the parallel component won't give any force, so, in a parallel direction with the field, the particle will move even, with the speed vcos alfa. In transversal direction the particle will have an even circular movement, with the speed v sin alfa.

    For the circular movement:

    qvBsin alfa=m*ac=mv^2*sin^2 alfa/R, R= mvsin alfa/qB

    The resultant movement is an even elicoid movement, the trajectory being the same with the thread.

    The time of one rotation doesn't depend on the particle's speed or the speed angle, formed with the lines of field.

    T=2piR/vsin alfa=2pi*m/qB=2pi/(Bq/m)

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    Posted by giorgiana1976 on Friday June 26, 2009 at 1:34 PM