#### Transcript Brief History of electromagnetism Contents

Brief History of electromagnetism Contents 1. History 1. Ancient times. 2. Mid-times 3. Early modern times. 2. Unification. Ancient times Amber rubbed with fur attracts bits of dust and hairs. Static electricity - spikes on cold, dry days, lightening. Lode stone compass Mid-times 1600. English scientist, William Giber, publishes “De Magnete”. 1700. Lectures and demonstrations given by various scientists using electricity and entertain audiences Mid-times 1700.Ben Franklin(1706-1790) Two kinds of charges: positive and negative Like charges repel, unlike charges attract Conservation of Charges: an isolated system has constant total charge Mid-times 1785. Charles Austin de Coulomb The force between two charges Q1 and Q2 is proportional to their product divided by the separation distance r squared inverse square law. 1790. Alessandro Volta finds chemistry acting on two dissimilar metals generates electricity. He later invents the voltaic pile-the battery. Early Modern times 1820. Hans Christian Oersted. – electric current affects compass needle 1820. Adre Marie Ampere in Pairs finds that wires carrying current produce forces on each other. 1820. Michael Faraday at royal Society develops the idea of electric field and studies the effect of currents on magnets and magnets inducing electric currents. Early Modern times 1860. James Clerk Maxwell, a Scottish physicist and mathematician, puts the theory of electromagnetism on mathematical basis. 1873.Maxwell publishes "Treatise on Electricity and Magnetism" in which he summarizes and synthesizes the discoveries of Coloumb, Oersted, Ampere, Faraday, et. al. in four mathematical equations. Maxwell's Equations are used today as the basis of electromagnetic theory. Maxwell makes a prediction about the connections of magnetism and electricity leading directly to the prediction of electromagnetic waves. 1885. Hertz shows Maxwell was correct and generates and detects electromagnetic waves. 1895.Guglielmo Marconi puts the discovery to practical use by sending messages over long distances by means of radio signals. Maxwell’s Equations Gauss' law for electricity Gauss' law for magnetism Faraday's law of induction Ampere's law J 1 E B 2 2 0c c t Chaos Order Einstein’s Dream Is there an underlying simplicity behind vast phenomena in Nature? Einstein dreamed to come up with a unified description But he failed to unify electromagnetism and gravity (GR) History of Unification planets electric apple magnetic electromagnetiesm gravity atoms Quantum mechanics mechanics g-decay b-decay Special relativity GR Quantum ElectroDynamics Electroweak theory String theory? Weak force a-decay Strong force Grand Unification? The End Thank you!