  We investigate the low-frequency electrodynamics in the vortex state of two
type-II superconducting films, namely, a moderate-to-strongly pinned Niobium
Nitride (NbN) and a very weakly pinned amorphous Molybdenum Germanium (a-MoGe).
We employ a two-coil mutual inductance technique to extract the complex
penetration depth, $\tilde{\lambda}$. The sample response is studied through
the temperature variation of $\tilde{\lambda}$ in the mixed state, where we
employ a model developed by Coffey and Clem (CC model) to extract the different
vortex lattice (VL) parameters such as the restoring pinning force constant
(Labusch parameter), VL drag coefficient and pinning potential barrier. We
observe that a consistent description of the inductive and dissipative part of
the response is only possible when we take the viscous drag on the vortices to
be several orders of magnitudes larger than viscous drag estimated from the
Bardeen-Stephen model.
