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History of Electromagnetic Waves

History of Electromagnetic Waves. Prof. Zbynek Raida Brno University of Technology. Contents. Radio waves: what’s that? Basic of electromagnetics Coulomb and charge invention Oersted, Biot, Savart and magnetism Ampere and currents Faraday and induction Maxwell and all together

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History of Electromagnetic Waves

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  1. History of Electromagnetic Waves Prof. Zbynek Raida Brno University of Technology

  2. Contents • Radio waves: what’s that? • Basic of electromagnetics • Coulomb and charge invention • Oersted, Biot, Savart and magnetism • Ampere and currents • Faraday and induction • Maxwell and all together • Hertz and electromagnetic waves • Towards applications (next lectures) raida@feec.vutbr.cz

  3. Introduction (1) raida@feec.vutbr.cz

  4. Introduction (2) raida@feec.vutbr.cz

  5. Electric Charge • 1777: Charles Augustin de Coulomb raida@feec.vutbr.cz

  6. Towards Magnetism (1) • 1820: • Opposite ends of a galvanic battery joined by a metallic wire: uniting conductor • The straight part of the wire placed horizontally above the magnetic needle, properly suspended, and parallel to it… Things begin in this state, the needle will be moved… Hans Christian Oersted • The effect of the uniting conductor passes to the needle through the glass, metals, wood, water, resin, stoneware, stones; … The effects, therefore, which take place in the conflict of electricity, are very different from the effects of either of the electricities. raida@feec.vutbr.cz

  7. Towards Magnetism (2) • 1820: Jean-Baptiste Biot raida@feec.vutbr.cz

  8. Towards Magnetism (3) • 1820: André-Marie Ampére raida@feec.vutbr.cz

  9. Towards Magnetism (4) • 1824: Magnet placed inside a helical coil but in no case did the magnet seem to affect the current. • 1825: Battery-connected wire put in parallel to another similar wire; the width of the separation gap was about two thicknesses of paper. The ends of the latter wire attached to a galvanometer exhibited no action. Michael Faraday • 1828: A copper ring was suspended by a threat and a bar magnet was placed inside the ring, but no induced current was detected. raida@feec.vutbr.cz

  10. Towards Magnetism (5) • 1831: He prepared a helical wire in a form of a cylinder, and then, a cylindrical bar magnet ¾ inch in diameter and 8.5 inches in length had one end inserted into the end of the helix cylinder – then it was quickly thrust in the whole length and the galvanometer needle moved – then pulled out and again the needle moved but in the opposite direction. This effect was repeated every time the magnet was put in or out and therefore a wave of electricity was so produced from mere approximation of a magnet and not from its formation in situ. Michael Faraday raida@feec.vutbr.cz

  11. Ampere versus Faraday raida@feec.vutbr.cz

  12. Maxwell (1) James Clerk Maxwell raida@feec.vutbr.cz

  13. Maxwell (2) • 1864: The agreement of the results seems to show that light and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws. James Clerk Maxwell raida@feec.vutbr.cz

  14. Electromagnetic Waves (1) • 1887: Heinrich Rudolf Hertz raida@feec.vutbr.cz

  15. . Thank you for your attention ! raida@feec.vutbr.cz

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