ABSTRACT
A compass needle itself consists of a North and South pole, it being a small magnet free to rotate on a spindle. A compass needle placed in the vicinity of the coil would tend to align itself with the field surrounding the coil. Now, outside the coil, the alignment results in the familiar observation that like poles repel and unlike poles attract. Inside the coil, the compass needle is still aligned with the field but we can no longer say that like poles repel and unlike poles attract. Rather, it is more scientifically appropriate to say that when two magnetic fields interact, they tend to align themselves. This tendency to alignment exerts a mutual torque (or moment) between the bodies producing the fields. This is another way of expressing the concept of a magnetic moment.
