# Magnetic Fields and Electric Fields [duplicate]

The expression $$\,\mathbf F_\mathrm G\boldsymbol{=}m\, \mathbf G\,$$ and $$\,\mathbf F_\mathrm E\boldsymbol{=}q\, \mathbf E\,$$ make sense, but is there any derivation for $$\,\mathbf F_\mathrm B\boldsymbol{=}q\,\left(\mathbf v\boldsymbol{\times}\mathbf B\right)$$?