  Inflationary magnetogenesis has long been assumed to be the most promising
mechanism for producing large-scale magnetic fields in our universe. However,
generically, such models are plagued with either backreaction or strong
coupling problems within the standard framework. This paper has shown that the
reheating phase can play a crucial role in alleviating those problems along
with CMB. Assuming the electrical conductivity to be negligible during the
entire period of reheating, the classic Faraday electromagnetic induction
changes the magnetic field's dynamics drastically. Our detailed analysis
reveals that this physical phenomenon not only converts a large class of
magnetogenesis model observationally viable without any theoretical problem but
also can uniquely fix the perturbative average inflaton equation of state,
$\omega_{\phi} = (p+2)/(p+2)$ during reheating given a specific value of the
large scale magnetic field. This observation hints the inflaton to assume the
potential of form $V(\phi) \sim \phi^p$ near its minimum with $p \gtrsim 3.5$
if one considers the limit of the present-day strength of the large scale
magnetic field to be $\mathcal{P}_{B0}^{\frac{1}{2}} \gtrsim 10^{-18}$ G. Our
analysis opens up a new avenue towards constraining the inflationary and
magnetogenesis model together via reheating.
