Magnetism is intimately related to special relativity. Maxwell’s equations are invariant under a Lorentz transformation; the electromagnetic wave equation gives the speed of light c. Many have explained magnetic force as a consequence of relativistic length contraction, for example Richard Feynman in page 13-8 of his ≪The Feynman Lectures on Physics, Volume II≫ and Steve Adams in page 266 in his ≪Relativity: An Introduction to Spacetime Physic≫. If magnetic force is really created by relativistic length contraction, we should be able to derive the expression for magnetic force from the length contraction formula. And indeed we can, as I will show below.

Please read the article at

PDF Relativistic length contraction and magnetic force http://pengkuanem.blogspot.com/2017/04/relativistic-length-contraction-and.html
or Word https://www.academia.edu/32664810/Relativistic_length_contraction_and_magnetic_force