Abstract: To judge whether the memristor can be interpreted as
the fourth fundamental circuit element, we propose a variable-relation
criterion of fundamental circuit elements. According to the criterion,
we investigate the nature of three fundamental circuit elements and the
memristor. From the perspective of variables relation, the memristor
builds a direct relation between the voltage across it and the current
through it, instead of a direct relation between the magnetic flux and
the charge. Thus, it is better to characterize the memristor and the
resistor as two special cases of the same fundamental circuit element,
which is the memristive system in Chua-s new framework. Finally, the
definition of memristor is refined according to the difference between
the magnetic flux and the flux linkage.