Generation of coherent radial electric fields in plasma by drift-wave turbulence driven by plasma inhomogeneities is ab initio studied using gyro-kinetic particle simulation for conditions of operational tokamaks. In particular, the effect of the electron-to-ion mass ratio on the entire evolution of the plasma is considered. It is found that the electric field can be increased, and the turbulence-induced particle transport reduced, by making smaller, in agreement with many existing experimental observations.