In this work the distribution of field quantities was numerically investigated using the finite element method. Besides the spatial distribution also the volumic frequency distribution of the field quantities was considered. For piezoelectric ceramic fibres the influence of annular electrodes on the measurement of the longitudinal piezoelectric coefficient was investigated. By changing the fibre dimensions and the electrode configuration within a wide range, the impact of these parameters was studied. According to the calculations the measurement is sufficiently exact for long and thin fibres. Moreover, dielectric 0-3-composites were investigated using simple unit cells. The effective dielectric permittivity and the frequency distribution of the electric field strength were calculated. The influence of volume fraction and shape of the embedded particles was investigated, and the impact of permittivity differences between matrix and particles was studied.