Recent research in plasmonics demonstrated merging different materials and shapes to form complex geometries with improved optical response. One of the most extensively used nanostructure is the coated nanosphere (nanoshell), which finds its application in diverse fields of medical, science and engineering. In this paper, we propose a compact impedance model of metallic core nanoshell. The model is based on time-varying approach by solving full dipole equation for the metallic core and impedance of the dielectric shell is derived using near-field components of the dipole field. The expressions for the absorption and scattering cross-sectional areas, and their behavior with change in the dielectric function are derived for the first time for nanoshell using voltages, currents and circuit elements, with their equivalence compared with exact solution. Additionally, the effects of changes in nanoshell parameters (dielectric constants, thickness of shell layer and radii of core) on the resonance frequency predicted by the proposed impedance model are analyzed. The simplified impedance model is based on parallel resonance circuit and contributes to the better understanding the behavior of nanoshell and facilitate cost-effectiveness solution for the next generation nanoshell based metamaterials.