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quote:Originally posted by daveshortsIf the electric current is changing you can have non-circular electric currents, if you have a wire with a large metal sphere attached at either end and you apply an AC electric field you will get a small current with no return path
quote:Originally posted by McQueengsmollinThe whole point is that a force ordinarily acts in the direction of the field not orthogonally to it. This whole concept of orthogonality has arisen out of the fact that a part of the circuit (i.e ., the straight wire ) has been attributed with properties which it does not possess . Namely that , a moving charge results in a magnetic field orthogonal to it . In truth the orthogonality of the field is due to the fact that the current is circular. A ring magnet or to take my earlier example a horse shoe magnet displays exactly the same type of field , orthogonal to the poles. There are no moving charges , ( apart from aligned electron spin ) in the magnet , yet the field is orthogonal in this case and different in the case of a bar magnet , how do you account for this ? An examination of the facts can only lead to the conclusion , that yes , the field around a wire does in fact resemble in every respect the field around a circular magnet . Yet the magnetism exhibited by a wire through which a current is flowing is attributed to one cause , the flow of electrons in the wire , while the field around a permanent magnet is attributed to another cause. This in itself is suspect attributing identical phenomenon to two different causative factors. Why is it so difficult to admit that the field around a wire ( loops emanating perpendicularly to the wire ) is due to the fact that the current in question is always a circular current. Or are you claiming the fact that the current is circular has nothing at all to do with the shape of the field around the wire and that it is solely due to the fact that the charges are moving ?
quote:Originally posted by McQueenWould you agree that a permanent magnet contains only stationary charges , even if they are aligned to give a strong magnetic effect. There are no moving charges , in the sense of traveling electrons , in a permanent magnet , is that a given ? In other words there is only one field , the stationary field . Then why does the field around a horse shoe magnet exactly resemble the field around a wire carrying a current ? . The field around the poles of such a magnet are orthogonal to the poles , in exactly the same manner as the field around a straight wire , which also in reality happens to be not straight but part of a circle. Yet you have just stated that such a field is due to the complex interactions between stationary and moving magnetic fields.Further coming back to the original gist of the post , you must realize that when Ampere and Oersted formulated these laws , they had no idea of what a current was , and no inkling that such things as electrons even existed. It was not unreasonable for them to assume that when they mapped the field around a straight wire , they assumed that the mapped field truly represented that around a straight wire , never realizing that the current was also flowing through the battery making a complete circle. Otherwise , I am sure the terminology field around a straight wire would never have been used. Furthermore if they had realized that the current was flowing in a circular path , it is probable that they would have immediately seen the similarity between the field around a circuit and that of a ring shaped magnet , since permanents magnets of all shapes were probably an indispensable part of the laboratory equipment of those days (i.e late 1700 to early 1800’s ).