Electromagnetic Theory
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
CONTENTS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Why EMF ?
What is EMF ?
Sources of EMF
Applications
Effects ( human, animals & plants)
Standards
Exposure levels and limits
Precautions &Recommendations
Why this Subject ?
Factors affecting EMF
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
1.Why a study on EMF ?
• Changes in social status &
behavior have increased the
electricity demand and invention
of advanced technologies
• To understand the happenings of
almost all the processes in the
universe.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
• EMF are present everywhere in our
environment .
• Everyone is exposed to a complex
mix of weak electric and magnetic
fields, both at home and at work.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
2. What is EMF ?
• Electric fields (E)
Due to static electric
charges
• Magnetic fields (H)
Due to motion of
electric charges
• Electromagnetic fields
Due to both time
varying E and H fields
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Electric Fields (E)
Magnetic fields (H)
Flux density (B)
Arises from
Voltage difference
Arises from current
flows, magnet
V/m
A/m, Magnetic flux
density T, G
Decreases with distance from the source
At higher frequencies ,
2
Power
Density
W/m
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
3.Sources of EMF
• Natural Sources
• Human made Sources
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Natural sources of EMF
•
•
•
•
Atmospheric fields
Geo magnetic field
Extra terrestrial fields
Living organisms
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Atmospheric fields
• Clouds getting charged, Lightning discharge
• Normal weather 200V/m (2V/cm)
• Lightning > 2-3MV/m
( 20kV/cm)
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Earth as a Capacitor
W = 7x 1012 J ( million fully charged 12V,
100AHr automobile storage batteries)
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Earth’s magnetic field
• Earth's static field 30µT ( equator)- 60µT
(poles)
• EM radiation 0.003 W/m2, up to 300kHz
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Extra terrestrial fields
RF radiation of cosmic origin observed
with Earth’s satellite
1.8 x 10-20 W/m2/Hz at 200 kHz to
8 x 10-20 W/m2/Hz at 10 MHz.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Human Generator
• Human body emits EMF 0.003 W/m2 up to
300kHz
( if the total body surface is 1.8 m2 , then the total
radiated power is 0.0054 W)
• walking slowly 0.1m/sec - 4µV/m
• Walking fastly
8m/sec - 400 µV/m
• A tilt of the head of 45 Deg. - 4µV/m at 0.2µT at
60Hz
• A fast nod in 0.16 sec.
- 40mV/m
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Heart Dipole
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Electric Fish
• Electric organ made up of modified
muscle or nerve cells
• Electric output of the organ Electric
organ discharge
(EOD) CEG,
Dr.S.Usa, Professor,DEEE,
AU Chennai
• Strong EOD- 10-500V, 1A - to stun the
prey - electric eel, electric catfish
• Weak EOD <1V - used for navigation,
electrolocation, electro communication
-Peter Elephentose Fish
• Wave shape of EOD -Cont. , Sinusoidal
• Brief, pulses with large gaps.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Human made sources Of
EMF
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
EMF sources
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
4. EMF Applications
Sl.
No
Frequency
Application
1
0.3-30 kHz Power line, electric appliances, medical
applications, electric furnaces, induction
heating, refining, VDUs
2
30-300 kHz Radio navigation, marine and aeronautic
communications, VDUs, power inverters
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
3
0.3-3
MHz
AM broadcasting,, sealing for
packaging, production
of
semiconductor material, medical
applications
medical
diathermy, magnetic
resonance imaging, dielectric heating,
wood drying and gluing
4
3-30
MHz
5
30-300 diathermy, magnetic resonance
MHz
imaging, dielectric heating, plastic
welding, food processing , particle
separation
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
6
0.3-3 UHF-TV, microwave ovens, medical
GHz diathermy, food processing, material
manufacture,
insecticide,
particle
acceleration, cellular
7
3-30 Radar,
satellite
communications,
GHz airborne weather radar, police, plasma
heating,
thermonuclear
fusion
experiments
8
30- Radar,
satellite
300 microwave relay
GHz
communications,
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
8/25/2022
24
VARIOUS VOLTAGE LEVELS
Low
Voltage
<1000 V
Medium
High
1000 V – 33 kV AC
33 kV – 220 kV AC
Extra high
220 kV – 765
kV
800 kV – 1000
kV
AC, DC
Valid Section
Secondary
Distribution
Primary Distribution
Secondary
Transmission
Primary Transmission
AC, DC
Primary Transmission
>1000 kV
HVDC
Primary Transmission
Ultra high
8/25/2022
System
AC
25
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
5. EFFECTS OF EMF
• on Human
• on animals
• on plants
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
EFFECTS ON HUMAN
• Tiny electrical currents exist in the
human body even in the absence of
external electric fields.
• Low-frequency E and H induce
circulating currents within the human
body, if sufficiently large could cause
stimulation of nerves and muscles or
affect other biological processes.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Effect on human health
Positive effects
• Medical diagnosis
• Restoration of movement in the limbs
• Termination of TB bacilli
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
On Human:
Negative effects
 Cancer
 Increased BP
 Depression
 Eye sight
 Brain cell damage
 Professional hazards
 Reproductive outcome
 Neurological (Alzheimer’s
disease) and psychiatric
diseases
• Cardiovascular
• Brain and behavior Hormonal
and immune systems
8/25/2022
Effects of ELF EMF
Electric field do not penetrate the body
significantly but they do built up a
charge on its surface
Magnetic field exposure to magnetic fields
cause circulating currents to flow in the
body
30
Effects of ELF EMF
On Humans:
Human body in a uniform electric field of 1 kV m-1 at 60 Hz showing
the external electric field and surface charge density on the body
surface: (a) in free space, and (b) in contact with perfect ground
(Stuchly & Dawson, 2000).
8/25/2022
31
Effects on animals
Effects of ELF EMF
• Neurological changes
systems in the brain
• night-time suppression
of melatonin etc.,
Cow- decreased milk yield and
shorter calving intervals
8/25/2022
32
Effects of ELF EMF
On Birds:
• mortality
• visibility is reduced
• orientation of birds is
affected
• Unable to pick grain
due to chattering
• Growth reduction
8/25/2022
Bees can be affected if the hive is
under (or close to) a power line and
they receive microshocks.
33
Threshold limits
•
•
•
•
•
•
•
•
Rats- 3 and 13 kV/m , 200 µT
Rabbits - 100 µT
Rodents - >50 kV/m
Baboons- 5–15 kV /m
miniature swine 30– 35 kV/m
Birds- 30 kV/m
Fruit flies- E> 1kV/m - 1.5 or 80 µT
Honey bees – sensitive to 0.025 µT (1000–7000µT,
found within 1m of the conductors, afects honey bee
olfactory learning, fight, foraging activity and
feeding)
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
On aquatic life
Undersea power cables could interfere
with the prey sensing or navigational
abilities of these animals in the
immediate vicinity of the sea cables.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
EFFECTS ON PLANTS
Application in agriculture
• Devitalisation and control of weed seeds
• Effective against soil borne pests and
pathogens
• In effective pollination
• Food processing
• Destruction of plant tumor without affecting
the plant
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
EFFECTS ON PLANTS (Negative)
• The growth characteristics like shoot length, root length, leaf area,
leaf fresh weight, specific leaf weight, shoot/root ratio, total
biomass content and total water content of the four crop plants
were reduced significantly
• Damage to trees is well known to occur at due to corona discharge at
the tips of the leaves.
• Reduced fruit yielding capacity
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Other effects
of EMF
Effects of ELF EMF
EMF Effects on Vehicles parked
near Line
EMF Effects on Pipe Line
/Fence/Cables
8/25/2022
38
EMF Effects Maintenance Worker
6.Standards for static electric
and magnetic fields
• 1994: the American Conference of
Governmental Industrial Hygienists (ACGIH)
• 1994: the International Commission on NonIonizing Radiation Protection (ICNIRP)
• 2010: ICNIRP (for limiting exposures to
Electric and Magnetic fields {1Hz-100kHz})
• 2004: A draft of new occupational exposure
guidelines from the European Union
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
STANDARDS FOR STATIC ELECTRIC AND MAGNETIC
FIELDS
• American Conference of Governmental Industrial
Hygienists (ACGIH)
• International Commission on Non-Ionizing Radiation
Protection (ICNIRP)
• Coupling mechanisms between fields and body
• Conclusion from the current scientific literature
• Guidelines for limiting EMF exposure
• Reference levels
 Precautionary approaches
 Communication
 WHO recommendations
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
The standards are based on the
foll. considerations.
•
To keep the electrical currents
induced by movement through the
static magnetic field to a level less than
those that occur naturally in the body.
• To keep the electrical currents
induced in large blood vessels by
blood flow to a level that will not
produce
hemodynamic
or
cardiovascular effects.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
• The pacemaker and prosthetic device
restrictions are considered
• Typical tolerances provided are 10% for
professionals of this field and 50% for
public.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
7.REFERENCE LEVELS FOR OCCUPATIONAL
EXPOSURE & GENERAL PUBLIC EXPOSURE
AS PER ICNIRP (2010)
Frequency
range Hz
Occupational
Exposure
General Public
Exposure
E- field
strength
E (kV m-1)
Magnetic
field strength
H (A m-1)
E- field
strength
E (kV m-1)
Magnetic
field strength
H (A m-1)
1–8
20
1.63 x 105 / f2
5
3.2 x 104 / f2
8 – 25
20
2 x 104 / f
5
4 x 103 / f
25 – 300
5 x 102 / f
8 x 102
2.5 x 102 / f
1.6 x 102
300 – 3 k
5 x 102 / f
2.4 x 105 / f
2.5 x 102 / f
6.4 x 104 / f
3 k – 10 M
1.7 x 10-1
80
8.3 x 10-2
21
ICNIRP exposure guidelines
European
power
frequency
Frequency
50 Hz
Mobile phone
base station
frequency
50 Hz 900 MHz 1.8 GHz
E (V/m) B (µT)
Public
exposure
limits
5 000
100
Power
density
(W/m2))
4.5
Occupation
al exposure
limits
10 000
500
22.5
Microwav
e oven
frequency
2.45 GHz
Power
density
(W/m2)
Power
density
(W/m2)
9
10
45
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Table of power density,E and time to
heat 10ltr of water 100C
Category
Power
E
density W/m2
Time
MW
transmitter
2.4x106
30.0 kV/m
18 min
IEEE safe
level for
human
2
27.5 V/m
5.8 hrs
100 µV/m
53X106 Years
FCC level for 27X10 -12
equipment
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Typical B of household appliances at
various distance
3cm
distance(
(µT)
6-2000
30cm
distance
(µT)
1m distance
(µT)
0.01-7
0.01-0.03
Electric
shaver
15-1500
0.08-9
0.01-0.03
Computer
0.5-30
<0.01
Electric
appliance
Hair dryer
Microwave
73-200
4-8
oven
Vacuum
200-800
2-20
cleaner
Limit at 30 cm distance
µT CEG,
Dr.S.Usa,<100
Professor,DEEE,
AU Chennai
0.25-0.6
0.13-2
WHO recommendations
• More bio-effects research is needed
• Need to pay careful attention to the
need for careful planning and quality
control of the research.
• The potential environmental effects of
EMF
should
be
reviewed
by
independent agencies.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
8.Precautionary approaches
• Strict adherence to existing national
or international safety standards
• Simple protective measures
• Consultation with local authorities
and the public in siting new power
lines or mobile phone base stations
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
• Communication: an effective system
of
health
information
and
communication among scientists,
governments, industry and the public
• This level of communication can
help raise general awareness of
programs dealing with exposure to
electromagnetic fields and reduce
any mistrust and fears.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Why this Subject ?
• To understand the working principle &
design
• To enhance & optimize the design
• EMI / EMC
• Invention of new applications
• Protect our environment
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
CODES OF ETHICS
• Engineering is a profession that makes
significant contributions to the economic
and social well-being of people all over the
world. As members of this important
profession, engineers are expected to
exhibit the highest standards of honesty
and integrity.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
As per IEEE
• To accept responsibility in making engineering decisions
consistent with the safety, health, and welfare of the
public, and to disclose promptly factors that might
endanger the public or the environment
• To avoid real or perceived conflicts of interest whenever
possible, and to disclose them to affected parties when
they do exist;
• To be honest and realistic in stating claims or estimates
based on available data;
• To reject bribery in all its forms;
• To improve the understanding of technology, its
appropriate application, and potential consequences
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
• To maintain and improve our technical competence and
to undertake technological tasks for others only if
qualified by training or experience, or after full disclosure
of pertinent limitations;
• To seek, accept, and offer honest criticism of technical
work, to acknowledge and correct errors, and to credit
properly the contributions of others;
• To treat fairly all persons regardless of such factors as
race, religion, gender, disability, age, or national origin;
• To avoid injuring others, their property, reputation, or
employment by false or malicious action;
• To assist colleagues and co-workers in their professional
development and to support them in following this code
of ethics.
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
PIONEERS OF
ELECTROMAGNETICS
Thales of Miletus 636-546 B.C
Pioneered in
electricity and
magnetism
William Gilbert
1540-603
A.D
Recognized that earth
is a huge magnet
Benjamin
Franklin
1706-1790
Established
conservation of
charge
Charles A de
Coulomb
1736-1806
Measured electric and
magnetic forces
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Karl F Gauss
1777-1855
Divergence theorem
Hans C Oersted
1777-1851
E
H
Michael faraday
1791-1867
H
E
James C Maxwell 1831-1879
Electromagnetic
theory
Heinrich Hertz
Radio waves
1857-1894
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Organization of EM Theory
Electro
statics
Magneto
statics
Electro
dynamics
Maxwell’s
Equations
Dr.S.Usa, Professor,DEEE, CEG,
AU Chennai
Electro
Magnetic
Waves