Give features of force on charge particle inside magnetic field.

Explanation

1. Magnetic force acted upon q electric charge moving with `vecv` velocity in magnetic field `vecB` is given by,
`vecF_(m)=q(vecvxxvecB)`
`thereforeF_(m)=qvBsintheta` where `theta` is angle between `vecvandvecB`.
2. Features :
(i) It depends on `q,vecvandvecB` charge of the particle, the velocity and the magnetic field.
3. Force on a negative charge is opposite to that on a positive charge so we can write
as `vecF_(m)=q(vecBxxvecv)`.
(ii) `F_(m)=qvBsinthetaorvecF_(m)=q(vecvxxvecB)or|vecF_(m)|=qvBsintheta` which is vector product of velocity and magnetic field. So, if `theta=0^(@)ortheta=180^(@)`, then
`F_(m)=qvBsin0^(@)=0orF_(m)=qvBsin180^(@)=0`

4. The force acts in a direction perpendicular to both the velocity and the magnetic field. Its direction is given by the screw rule or right hand rule as illustrated in figure (a) and (b).
5. Diagram (a) is for positive charge and diagram (b) is for negative charge.
(iii) The magnetic force is zero if charge is not moving as then v = 0.
`therefore` In magnetic force `F_(m)=qvBsintheta" "v=0`, then
`thereforeF_(m)=0`
Thus, only a moving charge feels the magnetic force but static charge does not.