Homes and office buildings are full of electrical wiring. Why are fields not high everywhere?
Most of the wires that pass through walls, floors, and ceilings are actually cables containing two or more current carrying conductors. At any point in time, the current is flowing in one direction on one wire, and in the opposite direction on the other wire. Since these wires are very close together inside the cable jacket, the magnetic field around one wire is cancelled by the opposite magnetic field around the other wire. The field is negligible a few inches from the wire. Problems occur when this balance is destroyed by wiring errors .
