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Electromagnetics: Its History and

Importance

Electromagnetics - embraces both electricity and magnetism

Elektron Greek Word of amber 

- electricity, electron and electronics are derived from it

Loadstone

natural magnetic rock found at a place calledMagnesia,

- from w/c is derived the word magnet & magnetism

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P ioneers of Electromagnetics

Name Dates Role played units(if any)

Thales of Melitus 636 546 B.C. pioneered in electricity & magnetism

William Gilbert 1540-1603 A.D. recognized that the earth is a huge Gilbert (Gb)

magnet 

Benjamin Fraklin 1706 1790 established conservation of charge

Charles de Coulomb 1736-1806 measured electric & magnetic forces C

Karl F. Gauss 1777-1855 enunciated divergence theorem gauss (G)

Alessandro Volta 1745-1827 invented voltaic cell  volt (V)

Hans C. Oersted 1777-1851 discovered that electricity could  oersted (Oe)

 produce magnetism

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Cont.

Name Dates Role played units(if any)

Andre M. Ampere 1775-1836 invented solenoid  ampere ( A)

Joseph Henry 1797-1878 made experiments leading to henry (H)

electric telegraph

Georg S. Ohm 1787-1854 formulated Ohms Law  ohm()

Michael Faraday 1791-1867 demonstrated that magnetism

could produce electricity  farad (F)

James P. Joule 1818-1889 established that heating is joule(J)

proportional to the square of 

the current

James C. Maxwell 1831-1879 founded electromagnetic theory  maxwell ( Mx)

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Name Dates Role played units(if any)

HeirichHertz 1857-1894 father of radio hertz ( Hz)

Gugliemo Marconi 1874-1937 made radio practical

Thomas A. Edison 1847-1931 invented incandescent light bulb

& built first electric power systems

Nikola Tesla 1856-1943 demonstrated value alternating tesla(T)

current

Albert Eistein 1879-1955 made Maxwells equations universal

through his theory of relativity

Cont.

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Fundamental Dimensions:

length l

mass m

time t

electric current I

temperature T

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Applications:

electric motors

generators

electronics radar

remote sensing

stationary communications satellites

speakers

Cont.

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The Static Electric Field

AndCoulomb¶s Law

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Magnetic fields are produced by electric currents, which can

be macroscopic currents in wires, or microscopic currents

associated with electrons in atomic orbits.

Tesla - SI unit for magnetic field

(1 Tesla = 10,000 Gauss).

Electricity

phenomenon associated with the presence and motionof electrons and other charged particles.

Electric Current

the directional motion of electrons

Electromagnetic Field a field being any region in which electric and magnetic

forces act.

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FLUX DENSITY

1 Tesla (T) ± 1 Weber per square meter (Wb/m2 )

1 Gauss (G) ± 1 Maxwell per square centimeter (Mx/cm2 )

1 Gauss (G) ± 1 x 10-4 T

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electric charge is the source of electric field ,

the electric field at any point in space can be mathematicallyrelated to the charges present - an isolated point charge.

1. Electric charge is a fundamental property of matter, as is mass or

dimension.

2. Charge is quantized:

there exists a smallest quantity ( quant um) of charge that can

be associated with matter.

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3

. The charge quantum is associated with the smallest subatomicparticles, and these particles interact through electrical forces

matter is organized and arranged through electrical interaction

4. Electric charge is an invariant:the val ue of charge on a particle does not depend on

the speed of the particle. In contrast, the mass of a particle

increases with speed.

5. Charge acts as the source of an electromagnetic field;

the field is an entity that can carry energy and momentum

away from the charge via propagating waves.

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Magnetic Field of Current

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DIV ERT. Gate DivertersP OSI T I ON. Positioning applications can

range from a simple ratcheting device to

precise variable positioning.

K IC K. Solenoid snap-acting response

and electric operation are beneficial

for part rejection processes in which

electronic interfacing with a

photosensor or some other sensor

is required.

LOC K/ LAT CH 

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Electric Force Example

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Where:

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Coulomb's Law

Like charges repel, unlike charges attract.

The electric force acting on a point charge q1 as a

result of the presence of a second point charge q2 is given

by Coulomb's Law:

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Practice ! 

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