Effect of electrically insulating materials on magnetically induced electrical currents in a tissue-like medium

Time varying magnetic fields can induce eddy currents in a conductor. Electrical currents also can be induced magnetically in the human body, and there has been considerable interest in the bioeffects of this phenomenon. We present an analytical model derived from Faraday's law and Coulomb's law that provides physical insight into how electrically insulating materials in a tissue-like medium redirect magnetically induced currents. The model shows that charge accumulates at the tissue-insulator interface to produce a secondary electric field. This field combines with the magnetically induced electric field to alter the net electric field in the vicinity of the insulator, causing the electric current to flow around the insulator. The model is supplemented by measurements of magnetically induced electric fields in a volume of physiologic saline solution. Good agreement is found among the model, the measurements, and a finite element analysis model of the experiment. © 2006 American Association of Physics Teachers.