A current impedance device for routing a time-varying electrical current in a piping structure comprising an induction choke. The induction choke is generally concentric about a portion of the piping structure such that during operation a voltage potential forms between the piping structure and an electrical return when the time-varying electrical current is transmitted through and along the piping structure, and such that during operation part of the current can be routed through a device electrically connected to the piping structure due to the voltage potential formed. The induction choke may be unpowered and may comprise a ferromagnetic material. A system for defining an electrical circuit in a piping structure using at least one unpowered ferromagnetic induction choke, comprises an electrically conductive portion of the piping structure, a source of time-varying current, at least one induction choke, a device, and an electrical return. The system can have various configurations and embodiments to define a plurality of possible electrical circuits formed using at least one induction choke to route time-varying current. An electric power transformer can also be incorporated. The system is adapted to provide power and/or communications for the device via the piping structure. One possible application of the system is in a petroleum well where a downhole device can send or receive power and/or communication signals via a piping structure of the well.