Brief History of electromagnetism

ContentsContents

1.1. HistoryHistory

1. Ancient times.1. Ancient times.

2. Mid-times2. Mid-times

3. Early modern times.3. Early modern times.

2. Unification.2. Unification.

Ancient times

AmberAmber 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-timesMid-times

1700.Ben Franklin(1706-1790)1700.Ben Franklin(1706-1790) Two kinds of charges: positive and Two kinds of charges: positive and

negativenegative

Like charges repel, unlike charges attractLike charges repel, unlike charges attract Conservation of Charges: an isolated system Conservation of Charges: an isolated system

has constant total chargehas constant total charge

Mid-timesMid-times

1785. Charles Austin de Coulomb1785. Charles Austin de Coulomb

The force between two charges Q1 and Q2 is The force between two charges Q1 and Q2 is proportional to their product divided by the proportional to their product divided by the separation distance r squared inverse square separation distance r squared inverse square law.law.

1790. Alessandro Volta finds chemistry acting on 1790. Alessandro Volta finds chemistry acting on two dissimilar metals generates electricity. He two dissimilar metals generates electricity. He later invents the voltaic pile-the battery.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

                         

     

                

                     

                              

        

t

E

cc

JB

22

0

1

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 UnificationHistory of Unification

gravity

electric magnetic

-decay

-decay

-decay

planets apple

electromagnetiesm

atoms

Quantum mechanicsmechanics

Special relativity

Quantum ElectroDynamics Weak force

Strong forceElectroweak theory

Grand Unification?

GR

String theory?

The EndThe End

Thank you!Thank you!