Final answer:
The rotation of molecules due to changing polarity of eddy currents is known as the dipole effect. The Doppler effect, however, is related to changes in wave frequency due to relative motion, and is not involved with molecules or eddy currents.
Step-by-step explanation:
The rotation of molecules due to changing polarity of eddy currents is known as the dipole effect. Eddy currents can induce a temporary dipole in a molecule, aligning it with the external magnetic field. This is part of the broader phenomenon of induction, where a conductor moving in a magnetic field, or vice versa, causes currents known as eddy currents. These currents can produce significant drag, termed magnetic damping. In contrast, the Doppler effect refers to changes in the observed frequency, intensity, or timbre of a sound or other waves due to the motion between the source and the observer, which is unrelated to the rotation of molecules due to eddy currents.