  The torque on a moving electric or magnetic dipole in slow motion is deduced
using the Lorentz transformation of the fields to first order in v/c. It is
shown that the obtained equations are independent of the model adopted for the
dipole, whether it is of Amperian or Gilbertian type, thus showing the complete
validity of the Amp\`ere equivalence principle even in dynamical conditions.
The torque is made of three terms: beside that due to the direct torque on the
dipole there are two more terms: one due to the torque on the associated
perpendicular dual-dipole caused by motion, while the other is the inertial
torque due to the displacement of the dipole which carries with it the field
linear momentum, or the hidden momentum.
