Physics
Oersted's Experiment
Oersted's Experiment demonstrated the relationship between electricity and magnetism. In 1820, Hans Christian Oersted observed that a current-carrying wire caused a nearby compass needle to deflect, indicating a magnetic field was produced by the current. This discovery laid the foundation for the development of electromagnetism and the understanding of the interplay between electricity and magnetism.
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eBook - PDF- Peter Graneau, Neal Graneau;;;(Authors)
- 1996(Publication Date)
- WSPC(Publisher)
CHAPTER 1 Evolution of the Nineteenth Century Newtonian Electrodynamics The Birth of Electromagnetism The concepts of electricity and magnetism have existed since the time of the ancient Greeks. Since then it has been believed that the attraction of iron by lodestone and of many kinds of matter by electrified amber had something in common. At least since the Middle Ages man had known that when lightning struck iron it could imbue this metal with magnetism. By the same token, the fire from heaven was capable of changing the polarity of a compass needle. Dibner [1.1] reported that in 1802, Romagnosi, a lawyer and physicist at the University of Parma in Italy, reversed the polarity of a compass by passing a galvanic current along the needle. This experiment came close to the discovery of electromagnetism which has been universally attributed to the Danish scientist Hans Christian Oersted (1777-1851), eighteen years later. Oersted, a professor of natural philosophy in Copenhagen, determined the direction in which a compass needle would turn when a straight wire with electric current flowing along it was brought near to the needle without touching it. One might ask why this particular experiment was singled out as the beginning of electromagnetism? Oersted felt so certain of the enthusiastic reception of his discovery that he had a paper printed for the occasion and sent to all scientists and journals of note. [1.2] The paper was dated July 21, 1820. It claimed that magnetic flux'encircled the current, but Oersted called this flux 'electric conflict'. Here was the missing link between electricity and magnetism. It has to be remembered that Oersted's explanation of the magnetic influence of an electric current came at a time when effluvia, ether, and ether vortices were not in vogue because of the success of Newton's and Coulombs action at a distance laws which avoided any reference to what was happening in the space between interacting bodies.
eBook - PDFFlash of the Cathode Rays
A History of J J Thomson's Electron
- Per F Dahl(Author)
- 1997(Publication Date)
- CRC Press(Publisher)
Grandly named the Royal Chemical Laboratory, it was indeed augmented by the king's contribution of own collection in 1815. As noted, a recurring theme of the German romantic movement was the unity of nature, and, in particular, of electricity and magnetism. Although skeptical of the more extreme views of Schelling and his followers, 0rsted's own belief in this unity, reinforced by his Wanderjahr contacts, determined his own scientific program and led straight to the experiments of 1820. As he himself wrote, 32 Electromagnetic Phenomena Unraveled Throughout his literary career, he adhered to the opinion, that the magnetical effects are produced by the same powers as the electrical. He was not so much led to this, by the reasons commonly alleged for this opinion, as by the philosophical principle, that all phenomena are produced by the same original power. [2-59] The years 1812-1813 saw him in Germany and France again. Though by now more critical of the philosophers, his guarded optimism in finding a relationship between electricity and magnetism by direct experiment surfaced at this time in an account of his own electrochemical system first published in Berlin [2-60] and extensively revised in a French version [2-61 ]: Magnetism exists in all the bodies of nature, as Bruckmann and Coulomb have proved. For this reason it is felt that magnetic forces are as general as electrical forces. One should test whether electricity in its most latent form has any action on the magnet as such. This experiment would offer some difficulty because electrical effects are always likely to be involved, making the observations very complicated. As to the circumstances of the actual experiments in the spring of 1820, 0rsted has left us several accounts, one written the following spring . . . . I was brought back to [experiments on the effects of an elec-tric current on a magnet] through my lectures on electricity, gal-vanism, and magnetism in the spring of 1820.
eBook - PDFEarly Electrodynamics
The First Law of Circulation
- R. A. R. Tricker, D. ter Haar(Authors)
- 2016(Publication Date)
- Pergamon(Publisher)
Part 2 This page intentionally left blank 1 A Oersted EXPERIMENTS ON THE EFFECT OF A CURRENT OF ELECTRICITY ON THE MAGNETIC NEEDLE* THE first experiments respecting the subject which I mean at present to explain, were made by me last winter, while lecturing on elec-tricity, galvanism, and magnetism, in the University. It seemed demonstrated by these experiments that the magnetic needle was moved from its position by the galvanic apparatus, but that the galvanic circle must be complete, and not open, which last method was tried in vain some years ago by very celebrated philosophers. But as these experiments were made with a feeble apparatus, and were not, therefore, sufficiently conclusive, considering the im-portance of the subject, I associated myself with my friend Esmarck to repeat and extend them by means of a very powerful galvanic battery, provided by us in common. Mr. Wleugel, a Knight of the Order of Danneborg, and at the head of the Pilots, was present at, and assisted in, the experiments. There were present likewise Mr. Hauch, a man very well skilled in the Natural Sciences, Mr. Reinhardt, Professor of Natural History, Mr. Jacobsen, Professor of Medicine, and that very skilful chemist, Mr. Zeise, Doctor of Philosophy. I had often made experiments by myself; but every fact which I had observed was repeated in the presence of these gentlemen. The galvanic apparatus which we employed consists of twenty copper troughs, the length and height of each of which was 12 in.; but the breadth scarcely exceeded 2 in. Every trough is supplied with two plates of copper, so bent that they could carry a copper Translation from Thomson's Annals of Philosophy, October 1820. Translated from a printed account drawn up in Latin by the author and transmitted by him to the Editor of the Annals of Philosophy. 114 EARLY ELECTRODYNAMICS rod, which supports the zinc plate in the water of the next trough.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
Maxwell's electromagnetic theory of light obviously involved the existence of electric waves in free space, and his followers set themselves the task of experimentally demonstrating the truth of the theory. In 1887, Prof. Heinrich Hertz in a series of experiments proved the actual existence of such waves. The discovery of electric waves in space naturally led to the discovery and introduction in the closing years of the 19th century of wireless telegraphy, various systems of which are now in successful use on shipboard, lighthouses and shore and inland stations throughout the world, by means of which intelligence is transmitted across the widest oceans and large parts of continents. ________________________ WORLD TECHNOLOGIES ________________________ Nikola Tesla, circa 1896 In 1891, notable additions to our knowledge of the phenomena of electromagnetic frequency and high potential current were contributed by Nikola Tesla. Amongst the novel experiments performed by Tesla was to take in his hand a glass tube from which the air had been exhausted, then bringing his body into contact with a wire carrying currents of high potential, the tube was suffused with a pleasing bright glow. Another experiment was to grasp a bulb that was suspended from a single wire attached to a high potential, high frequency current circuit, when a platinum button within the bulb was brought to vivid incandescence, the experimenter at this time standing on an insulating platform. The frequency and potential involved in the experiments made by Tesla at this time were of the order of one or more million cycles and volts. For further information relative to these experiments the reader may be referred to Tesla's Experiments with Alternate Currents of High Potential and High Frequency. End of the century The theories regarding electricity were undergoing change at the end of the 19th Century.
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