[en] For ohmically driven tokamak plasma, the total plasma current is composed of ohmic current and internal self-consistent component. For a simplified Spitzer resistivity model, the toroidal current profile is determined by the electron temperature profile and the effective charge number Z_eff profile at each time. The derivation of the fundamental equation to determine this equilibrium configuration is given. In the large aspect ratio approximation, analytic solution on equilibrium configuration with small non-circular deformations is obtained for sawtoothing plasma. (authors)