# Is magnetic field a consequence of special relativity (length contraction and time dilation)

According to Lorentz force equation a charge moving in our frame experiences magnetic force but from the frame of reference of the charge it experiences only electric force. I have heard that magnetic phenomenon are due to special relativity but did not get it clearly. Can you help?

If you have two (say) positive free charges that start at rest, they will drift apart due to Coulomb repulsion. You can (if you want) measure the force between them by timing how long it takes them to travel a distance $s$ and then using $s={1 \over 2} a t^2$ and $F=ma$