A system and methods for drilling a well in a field having an existing well are provided. In accordance with one embodiment, a method of drilling a new well in a field having an existing well includes drilling the new well using a bottom hole assembly (BHA) having a drill collar divided by an insulated gap, generating a current on the drill collar of the BHA while drilling the new well, and measuring from the existing well a magnetic field caused by the current on the drill collar of the BHA. Using measurements of the magnetic field, the relative position of the new well to the existing well may be determined.