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8/8/2019 Electromagnetics ECE
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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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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: