Drag of Field

When a conductor is moved through a field so that a current is generated in it, the field due to that current blends with the other field and with its lines of force, distorting the field, thereby producing a drag upon its own motion, because lines of force always tend to straighten themselves, and the straightening would represent cessation of motion in the conductor. This tendency to straightening therefore resists the motion of the conductor and acts a drag upon it.