It is becoming standard practice to make electric blankets with minimal external magnetic field. Each wire is paired with another wire that carries current in the opposite direction. How does this reduce the external magnetic field? It is becoming standard practice to make electric blankets with minimal external magnetic field. Each wire is paired with another wire that carries current in the opposite direction. How does this reduce the external magnetic field? The two magnetic fields produced will be perpendicular, so the resultant vector will be very small. The two magnetic fields produced will be in the same direction, so they will not affect the baby at all. The two magnetic fields produced will be in opposite directions, so they will mostly cancel each other out.