[en] The effect of additional cooling and heating of electrons on expansion of collisionless plasma plasmoids of different geometry and dimensions is numerically investigated. It is shown that parameters of expanding plasmoids following additional cooling or heating, to rather a high degree of accUracy, are described by the effective time tau* which is determined by the ratio 1/tau*=1/tau sub(0)+1/tau (where tau₀=characteristic time of electron cooling without additional cooling and heating, tau=characteristic time of additional heating and cooling)