The correct definition of electromagnetic momentum in matter, either Abraham’s g A = (1/4 π c) (
E × H ), or Minkowski’s g M = (1/4 π c) ( D × B ) has been a theme of controversy for a century.
Therefore, we can find those who favor one or the other of these proposals. We present here an
alternative view, considering that both of the aforementioned equations are equivalent since they
pertain to different balance equations derived from the macroscopic Maxwell equations. This is done
through their application to a device proposed by Lai in 1980, and recovering his results. Advanced
undergraduate and graduate students can find in this work an introduction to a controversial issue
and an alternative point of view about it.