Derived force on moving charge in uniform magnetic field with velocity `vecv_`.

Explanation

1. Current induced from moving charge q with velocity `vecv` form uniform sectional wire,
`I=nAvq`
`thereforeIdvecl=nAvqdvecl`
2. Magnetic force acting on `Idvecl` small current carrying element in uniform magnetic field `vecB` is given as,
`dvecF=IdveclxxvecB`
`=nAvecvqdlxxvecB`
`thereforedvecF=nAqdl(vecvxxvecB)" "...(1)`
but nAdl = number density of charge in dl element.
3. Magnetic force on q electric charge,
`vecF_(m)=(dvecF)/(nAdl)=(nAdlq(vecvxxvecB))/(nAdl)`
`thereforevecF_(m)=q(vecvxxvecB)`