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


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Amber rubbed with fur attracts bits of dust and hairs.
Static electricity - spikes on cold, dry days, lightening.
Lode stone compass
Mid-times
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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.
–
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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
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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
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Faraday's law of induction

Ampere's law
J
1 E
 B 
 2
2
 0c c t
Chaos
Order
Einstein’s Dream
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
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!