The electrical interaction between a particle and a boundary in an electrolyte solution is of both fundamental and practical significance. We consider the case of a spheroid, which can be nonrigid, in a spherical cavity under both constant potential and constant charge density. The influences of the key parameters, including the valence of electrolyte, the level of surface potential, surface charge density, fixed charge density, and the sizes of cavity to particle, on the electrical interaction energy between the particle and the cavity are investigated. The results of numerical simulation reveal the following: (1) For the case of constant potential, if a particle is close to the cavity surface, the charge on the surface which has a lower potential may reverse its sign. (2) For the case of constant charge density, the electrical interaction energy between particle and cavity may change its sign from negative to positive as the charge density increases for the case of a rigid particle. In this case, both a dynamic equilibrium state and a static equilibrium state exist; the electrical interaction energy is negative in the former and is positive in the latter. These are not observed for a soft particle. (3) If the cavity surface remains at constant potential, the electrical repulsive force between particle and cavity for a rigid particle is greater than that for a soft particle, and the reverse is true if the cavity surface remains at constant charge density.