Electromagnetism is a branch of Physics, deals with the electromagnetic force that occurs between electrically charged particles. The electromagnetic force is one of the four fundamental forces and exhibits electromagnetic fields such as magnetic fields, electric fields, and light. It is the basic reason electrons bound to the nucleus and responsible for the complete structure of the nucleus.
2. Contents
Introduction.
About Electromagnetism.
Few Important Laws.
Few Important Equations.
Application.
Electromagnetic Spectrums.
3. Electromagnetism is one of the
fundamental forces of nature. It is
responsible for all of the everyday
things we see, except gravity.
Introduction
Light, life, and the bonding of
atoms into molecules are all
due to electromagnetism.
4. • Since the dawn of humanity, people have
been aware of electricity in lightning.
• Electric fish and rays were known in
ancient times.
• The static electrical property of amber
was investigated by the ancient Greeks.
• These natural electrical phenomena were
thought to be due to the will of the gods.
Electricity
5. • Static electricity was
investigated extensively during
the 18th century
• The concepts of electrostatic
forces and charge were
discovered
• Volta discovered that electricity
could be generated by chemical
reactions, leading to the battery
and the idea of voltage, which
bears his name.
.
Electricity
6. Coulomb discovered that the force
between two charged particles is
inversely proportional to the square of
the distance between them.
Electricity
7. • Stories of magnetism from China and ancient
Greece date back over 2000 years.
Natural magnets, made of magnetite, were
considered to possess magical powers.
• People soon realized that magnetite, when
made into the shape of a pointer and floated
on water, always pointed in a north-south
direction, creating a primitive compass.
• This led to the name lodestone, or ‘leading
stone’.
Magnetism
8. The navigational compass was first
recorded in China, around 1100, and then
shortly afterwards in Europe.
Magnetism
9. • The development of the compass
led to vastly improved navigation
– especially far from land – and
led eventually to the Age of
Discovery.
• The first artificial magnets were
produced in 1740
• Modern magnets, based on rare
earth elements, can be very
powerful.
.
Magnetism
10. • The 19th century saw the first
concrete links between electricity
and magnetism.
• Øersted discovered that a wire
carrying electric current
produces a magnetic field.
• Ampere discovered the force
between two current carrying
wires.
The Golden Age
• Faraday discovered electromagnetic induction; the process by
which a changing magnetic field produces an electric field.
11. • The Scottish physicist, James Maxwell,
published "A dynamical theory of the
electromagnetic field," which linked
electricity, magnetism, and light.
• Maxwell’s theory was used to explain how
oscillating electric currents in wires
produce electromagnetic waves, such as
radio waves.
Electromagnetism
12. • Hertz clarified and expanded the
electromagnetic theory of light that had
been put forth by Maxwell.
• He was the first to satisfactorily
demonstrate the existence of
electromagnetic waves.
Electromagnetism
13. • Maxwell’s theory was used by Einstein to
develop his theory of special relativity.
• Einstein explained the photoelectric effect.
• In 1940, this led to quantum electrodynamics –
the part of quantum mechanics that deals with
electromagnetism.
Electromagnetism
16. in A2s4 kg-1m−3 or C2N−1m−2 or F m−1
1642-1727
Fax of a 1682 letter from Newton to
Dr William Briggs,
commenting on Briggs' "A New
Theory of Vision"
1736-1806
Newton & Charles Coulomb
1612/9/2019
21. • total electric flux through a closed surface is equal to the total charge
enclosed by the surface.
𝑀𝑎𝑡ℎ𝑒𝑚𝑎𝑡𝑖𝑐𝑎𝑙𝑙𝑦
∯ 𝐷. 𝑑𝑠 = Qen
Ψ = ∯ 𝐷. 𝑑𝑠 = Qen
Ψ = ε∯ 𝐸. 𝑑𝑠 = Qen
∯ 𝐵. 𝑑𝑠 = 0 or µ∯ 𝐻. 𝑑𝑠 = 0
Gauss law
2112/9/2019
22. • Used to calculate the magnetic field due to a current carrying
conductor.
• Magnitude of the magnetic field at any point P due to a small current
element I.dl ( I = current through the element, dl = length of the
element) is -
2
sin
.
4
1
r
Idl
dH
Biot - Savart Law
2212/9/2019
23. Comparison - Coulomb’s laws and Biot Savart laws
• Both the electric and magnetic field depends inversely on square of distance
between the source and field point.
• Charge element dQ producing electric field is a scalar whereas the current
element IdL is a vector quantity having direction same as that of flow of current.
• According to coulomb’s law ,the magnitude of electric field at any point P
depends only on the distance of the charge element from any point P.
• According to Biot savart law, the direction of magnetic field is perpendicular to
the current element as well as to the line joining the current element to the point
P.
2312/9/2019
24. Ampere’s circuital law
Ampere’s Circuital Law states that the line integral of H about any closed
path is exactly equal to the direct current enclosed by the path.
2412/9/2019
27. James Clerk Maxwell
Professor of Natural Philosophy – King’s College, London
Unified theory of Electricity, Magnetism & Light
in classical Physics
2712/9/2019
34. • In 1887, Heinrich Hertz demonstrated
the reality of Maxwell's electromagnetic
waves by experimentally generating radio
waves in his laboratory.
• Their frequencies range from 300GHz to
as low as 3kHz.
• Radiofrequency is a rate of oscillation in
the range of radio waves, it refers to
electrical rather than mechanical
oscillations.
• Radiofrequency energy is used in medicine
e.g. MRI and RFA.
Heinrich Hertz
RADIOWAVES
3412/9/2019
35. MRI and RF (Radio Frequency)
• Used to produce images of soft
tissues, fluid, fat and bone.
• Uses strong superconducting
magnet with a magnetic field
strength 40,000 x that of the
Earth’s.
• It is used to diagnose many
problems e.g. helps identify
tumors.
Diagram of an MRI scanner
3512/9/2019
38. In 1888, Heinrich Hertz was the first
to demonstrate the existence of
radio waves by building a spark gap
radio transmitter that produced 450
MHz microwaves.
Microwaves have typically 300GHz
to 300MHz
Heinrich Hertz38
12/9/2019
MICROWAVES
39. Hyperthermia therapy is a type of
medical treatment in which body
tissue is exposed to slightly higher
temperatures to damage and kill
cancer cells or to make cancer cells
more sensitive to the effects of
radiation and certain anti-cancer
drugs.
Cancer cells being targeted
by microwaves3912/9/2019
Microwave Heat Therapy
42. • Can be detected by the human eye.
• Wavelengths range from 750-400nm.
• In the 17th Century, Isaac Newton explained the
optical spectrum in his book ‘Opticks’. He
divided the spectrum into seven named
colours: ROYGBIV.
• The actual concept of a visible ‘spectrum’ was
defined in the early 19th century when light
outside the visible range was discovered e.g.
Johann Ritter with Ultraviolet Light.
Sir Isaac Newton
4212/9/2019
VISIBLE LIGHT
43. Allows us to look inside the human body
through a narrow, flexible scope.
It is mostly used to diagnose problems in
the oesophagus, stomach and intestines,
including ulcers, bleeding and tumours.
Typically optical fibres are used to transfer
light to the end of the endoscope and a
miniature video camera records the image,
and viewed on a video screen.
Endoscope inside the body
4312/9/2019
Endoscopy/ Keyhole Surgery
44. • Premature babies sometimes have
jaundice.
• This makes them look yellow and is due
to excess bilirubin, the yellow pigment
in bruises.
• It is usually harmless but can be treated
using blue light.
• The blue light breaks down the bilirubin
so that it can be excreted as urine.
4412/9/2019
Blue Light Jaundice Treatment
46. • EM radiation between 10-400 nm.
• Johaan Wilhelm Ritter- 1801.
• Primary source from Sun.
Sun over UV filter.
4612/9/2019
Ultraviolet Radiation
Ultraviolet light in treatment of Psoriasis and
Vitiligo
Psoriasis
Vitiligo
47. Ultraviolet light hardening a patient’s filling
Ultraviolet light waves produce free
radicals that activate the catalyst and speed
up polymerisation of the composite resin.
4712/9/2019
Ultraviolet light in Dental Care
Ultraviolet light against germs
• Microbial Sterilization- using mercury
vapour lamps, which at specific
wavelengths such as 254nm can
sterilize germs
Ultraviolet light’s effect on cell data.
49. They were discovered
serendipitously by German Physicist
Wilhelm Roentgen in 1895.
Roentgen was working with electron
beams in discharge tubes.
In the early days many patients and
doctors developed radiation sickness
since they were shining x-rays in all
directions for large amounts of time.
Wilhelm Roentgen
4912/9/2019
Discovery of X-Rays
50. The free electron collides with the
tungsten atom, knocking an
electron out of a lower orbital. A
higher orbital electron fills the
empty position, releasing its
excess energy as a photon.
The free electron is attracted to the
tungsten atom nucleus. As the
electron speeds past, the nucleus
alters its course. The electron
loses energy, which it releases as
an X-ray photon.
5012/9/2019
X-Ray photon emission from Tungsten
53. • EM Radiation high frequency
• High energy photon- kill cancer
cells
• Produced by decay from high
energy states of atomic nuclei
• Discovered in 1900 by Paul Villard.
(right)
Paul Villard 5312/9/2019
GAMMA RAYS
