This shows how the length-contracted Coulomb force is the cause of magnetic fields, and also the cause of magnetic forces on moving charges. Both of these result from (and act on) current-elements q"v"=IΔ"s", which include moving charges (that may also exert electrostatic forces) and currents in neutral wires (that exert no electrostatic forces). If the positive charge q in the figure moves to the right, it feels an upward Coulomb repulsion because to that moving charge protons (drawn red in the magnified circle) of atoms in the neutral wire below appear closer together due to length contraction than do the uncontracted electrons (drawn blue in the magnified circle) moving along with q.