Embodiments herein describe a user device that includes a dual purpose coil (or inductor) used when performing inductive sensing and when transferring electrical power to the user device. When performing inductive sensing, the user device couples the coil to a sensing circuit which measures a resistivity of a lossy material inductively coupled to the coil. In one embodiment, the user device may be worn on the wrist of the user so that the sensing circuit measures the resistivity corresponding to the flow of blood in an artery or vein. By monitoring changes in the resistivity of the blood or artery, the user device can identify the heartbeat of the user. When transferring electrical power, the user device couples the coil to a charging circuit which receives the power provided by an external charging device that is inductively coupled to the coil.
