  A nonlinearly enhanced electrical reactance, $\Im Z$, under a large AC
current has been measured to explore emergent inductors, which constitute a new
class of inductors based on the spin-transfer torque effect. A nonlinear $\Im
Z$ has been observed in conducting magnets that contain noncollinear spin
textures and interpreted as the realization of an inductance due to
current-induced spin dynamics. However, curious behavior has concomitantly been
observed. For instance, the nonlinear $\Im Z$ always has a cutoff frequency of
$10^0$--$10^4$ Hz, which is much lower than the resonance frequency of a
ferromagnetic domain wall, $\sim$10$^7$ Hz; furthermore, the temperature and
magnetic field variations in $\Im Z$ appear to be considerably correlated with
those in the temperature derivative of resistance. This behavior appears to be
difficult to understand in terms of the current-induced spin dynamics, and
therefore, the earlier interpretation of the nonlinear $\Im Z$ should be
further verified. Here, we theoretically and experimentally show that
time-varying Joule heating and its impact on the AC electrical response can
naturally explain these observations. In the experimental approach, we study
the nonlinear AC electrical response of two conducting materials that exhibit
no magnetic order, CuIr$_2$S$_4$ and 1$T$'-MoTe$_2$. Under time-varying Joule
heating, a nonlinearly enhanced $\Im Z$ with the curious behavior mentioned
above is observed in both systems. Our study implies that the nonlinear $\Im Z$
previously observed in noncollinear magnets includes a considerable
contribution of the Joule-heating-induced apparent AC impedance.
