Velocities of charged cloud and precipitation particles in thunderclouds change because of the electrical forces acting on them. It is shown in this paper that this change in their velocities will cause a change in their concentrations in the regions of the cloud having intense electrification. These changes in the concentrations of cloud and precipitation particles have been calculated here in a simplified model. In accordance with the recent observations, small regions of the cloud having strong electric fields imbedded in large scale but comparatively weaker electric fields have been assumed to exist over short periods of time inside thunderclouds. No particular charge generating mechanism has been considered. However, cloud particles have been assumed to carry positive charge and the precipitation particles negative charge. A uniform and constant updraft has been assumed to exist for short periods of time in these small regions of the cloud. The results depict accumulation of the particles of certain sizes and charge densities in the regions of cloud having intense electrification. Dependence of this accumulation of particles on the electric field, charge and size of the particles, updraft velocity, and the size of the region of intense electrification has been studied. Variations of these accumulations with time have also been examined. Some possible consequences and implications of these calculations have been broadly discussed.