A two-dimensional finite difference time domain method was employed to investigate the electromagnetic field in a microwave applicator filled partially with a dielectric material, operating in the dominant TE10 mode at a frequency of 2.45 GHz. The power distributions developed in the applicator and inside a lossy material are calculated. Results show correlations between the power absorption ratio and physical parameters, e.g. the position of the dielectric in the applicator and permittivities of the dielectric, which are dominant in the heating process. In particular, the energy absorption ratio strongly depends on the position of the dielectrics. which shows a sharp maximum when the dielectric is located around the middle of the applicator. In addition, power absorption ratios are calculated according to the definition newly proposed in this study, and they are compared with those obtained experimentally.