Question

How can you find out whether the magnetic field at a point is due to some current carrying conductor or due to earth?

Answer 1

Place a compass needle at the given point. If it stays in the north-south direction, then the magnetic field is due to earth. If the needle points along any direction other than north-south direction, then the field is due to some current carrying conductor. If the current is switched off, the needle will orient itself along the north-south direction.

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