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The theory of the scattering of electro-magnetic radiation by a nano-particle (NP) has been developed intensively during the last decades. Recent developments in this theory encompass the scenario of the interaction between a charged sphere and electromagnetic radiation. One of the interesting outcomes of this new development indicates that the extinction and scattering of a propagating light beam as a result of a charged sphere in the propagation path is higher than for a neutral sphere. We would like to use this phenomenon in order to manipulate light for applications such as a variable attenuator or an optical filter. The scheme under consideration comprises charged NPs located between two plates of capacitor. The NP position is controlled by the capacitor voltage. The NPs are also subject to gravitational force. Different positions of the NP provide different values of attenuation. In this paper we derive a mathematical model to describe the interaction between the propagating light and charged NP in the proposed scheme. Our results indicate that for the given parameters 10 dB variable attenuation is achievable.