Kobayashi & Suda (1994) proved that the ratio had a definite value determined by the frequencies used and that the ratio indicates the location of the file tip in the canal. The quotient of the two impedances is nearly 1 when the tip of the file is some distance from the canal terminus. When the file is not at the minor apical foramen, the distance between the two plates of the model capacitance is high. Therefore, according to equation 3, the magnitude of the capacitance is negligible. Hence, the ratio of equation 8 will turn