Physics 2102 Gabriela Gonz lez James Clerk Maxwell 1831 1879 S S S S S S S S S S C very suspicious If we are charging a capacitor there is a current left and right of the capacitor Thus there is the same magnetic field right and left of the capacitor with circular lines around the wires There is an electric field inside the capacitor But no magnetic field there With a compass we can verify there is indeed a magnetic field equal to the field elsewhere But there is no current producing it Maybe we can make it right We calculate the magnetic field produced by the currents at left and at right using Ampere s law We can write the current as q CV C 0A d V Ed E EA Maxwell proposed it and it was confirmed B B B i i E Fields without sources A solution to the Maxwell equations in free space is a traveling wave 0 1 256 10 6 Tm A 0 8 854 10 12 C2 Nm2 0 0 Tm A C2 Nm2 TsC Nm Ns Cm sC Nm s2 m2 electric and magnetic forces can travel The velocity of the Maxwell waves is 3 108 m s The electric waves travel at the speed of light Light itself is a wave of electricity and magnetism First person to prove that electromagnetic waves existed Heinrich Hertz 1875 1894 First person to use electromagnetic waves for communications Guglielmo Marconi 1874 1937 1909 Nobel Prize first transatlantic commercial wireless service Nova Scotia 1909 Is there an ether they ride on Michelson and Morley looked and looked and decided it wasn t there How do waves travel Electricity and magnetism are relative Whether charges move or not depends on which frame we use This was how Einstein began thinking about his theory of special relativity We ll leave that theory for later maybe
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