We analyse the force acting on a moving dipole due to an external electromagnetic field and show that the expression derived in Vekstein (1997 "Eur. J. Phys." 18 113) is erroneous and suggest the correct equation for the description of this force. We also discuss the physical meaning of the relativistic transformation of current for a closed circuit and carry out the analysis of a number of particular physical problems, which are important from the educational viewpoint. (Contains 4 footnotes and 1 figure.)