Self-consistent fluid and particle-in-cell Monte Carlo (PIC-MC) models have been used to study the electrical characteristics of rf discharges in clean and dusty plasmas. Numerical results in pure helium and silane and in dusty argon are compared with experimental measurements. The presence of large concentration of dust particles in the plasma modifies considerably the electrical characteristics of the discharge. The discharge impedance becomes much more resistive in presence of dust particles. Depending on the geometry of the reactor the appearance of electrostatic traps for negatively charged particulates has been studied with a 2D fluid model.