Detection Coil, Detection Apparatus, and Detection System

A detection coil includes a first group of coils, a second group of coils, and a third group of coils that are continuously wound and coaxial, and the second group of coils is located between the first group of coils and the third group of coils. A coil that generates the first magnetic field is coaxial with the first group of coils, the second group of coils, and the third group of coils. A sum of the induced electromotive forces of the first group of coils, the second group of coils, and the third group of coils is zero. When a metal foreign matter exists, a sum of the induced electromotive forces of the first group of coils, the second group of coils, and the third group of coils is not zero.