How will you identify whether the magnetic field at a point is due to the earth or due to some current carrying conductor?

Explanation

We know that a freely suspended magnetic needle always pionts to north-south direction due to earth's magnetic needle always rests in north-south direction, the magnetic field is due to earth, and if this magnetic needle turns to some other direction and returns back to north-south when the current is switched off, then the magnetic field is due to a current carrying conductor.