An electromagnetic field is produced by moving electrically charged objects and affects other charged objects near it. It is one of the fundamental forces of nature and results from a combination of electric and magnetic fields. Electromagnetism underlies many daily phenomena and is governed by four main laws. Electric fields arise from voltage while magnetic fields arise from current flow. Electromagnets have many uses including in electric bells, sorting scrap metal, and speakers. Transformers change voltage levels in power transmission lines to reduce energy losses. Exposure to electromagnetic fields is increasing due to modern technology but typically does not pose health risks.

1. ELECTROMAGNETIC FIELD (EMF)

2. PRESENTED BY
GROUP NO: (B)
STUDENTS NAMES:
1. DIPANKAR PAIK D192012409
2. HABIB SARDAR D192012411
3. ISHAN ADAK D192012412
4. LOKNATH MRIDHA D192012415
5. MRIGANGA BAIDYA D192012417
6. NAZMUL HAQUE MOLLAH D192012418

3. ELECTROMAGNETIC FIELD
• An electromagnetic field (also EMF or EM
field) is a physical field produced by moving
electrically charged objects.
• It affects the behavior of charged objects in
the vicinity of the field.
• The electromagnetic fiekd extends
indefinitely throughout space anddescribes
the electromagnetic interaclion.
• It is one of the four fundamental forces of
nature (the others aregravitation, the weak
interaction, and the strong interaction).
• Tha field can be viewed as the combination
of an electric field and a magnetic field.

4. ELECTROMAGNETISM
• Electromagnetism is one of the fundamental
phenomenon in nature. Itis responsible for
almost all the phenomena in our daily life.
• Electromagneti sm spans both electric tlelds
and magnetic flelds
• These are Gauss's laws in Electrostatics,
Gauss's law inMagnetism, Ampere's law and
Faraday's law
• In order to fuly undersland Electromagnetism,
we have to look at thefour laws that govern
electricity and magnetlsm.

5. ELECTIC FILEDS AND MAGNETIC FIELDS
ELECTRIC FIELDS
1. Electric lields arise
tromvaltage
2. Their strength is
maasuredIn Wolts per
meter (V/m)
3. Field strength
docreases with
distance ftrom the
source.
4. Most building materials
field electric fields to
some extent.
MAGNETIC FIELDS
1. Magnetic fields a rise
from current flow
2. Their strength is
measured in amperes
per meter (a/m)
3. Magnetic fields exits as
soon as a devices is
switched on and
current flows
4. Field strength
decreases with
distance from the
source

6. USE FOR ELECTROMAGNETS
• An electromagnet does all the things that
ordinary magnets can do, but you can switch
them on and off.
• An electric bell – uses an electromagnet to
rapidly pull the hammer over to the gong then
release it.
• For sorting scrap – an electromagnet can be
used to pick up and put down magnetic
materials, sorting them from non-magnetic
scrap.
• In speakers – an electromagnet is used to
move a cone very rapidly, causing sound
waves.

7. USE FOR ELECTROMANETIC
Diagram of an
electric bell

8. USE FOR ELECTROMAGNETS
AN ELECTROMAGNET
BEING USED TO PICK
UP SCRAP

9. THE MOTOR EFFECT
“A CONDUCTOR CARRYING AN ELECTRIC CURRENT MAY EXPERIENCE A FORCE WHEN PLACED
IN TO A MAGNETIC FIELD”
To increase this force:
▪ Increase the current
▪ Increase the number of coils
▪ Increase the strength of the
magnet
▪ Increase the length of
conductor in
the field
To reverse this force:
▪ Reverse the direction of the
current
▪ Reverse the direction of the
(permanent) magnetic field

10. A SIMPLE DYNAMO
 If the conductor forms part of
a
circuit, a current will flow.
 In a dynamo, a coil is rotated
inside a magnetic field, causing
an
alternating current to flow.
 You can use the right hand
rule to
prove to yourself that a current
will
flow all the way around the coil
of
wire when the coil is rotated.

11. TRANSFORMERS
 A coil of wire is wound on to
one
side of a soft iron core. This coil is
called the primary coil.
 When an alternating current
flows
through this wire, an alternating
electromagnetic field is set up in
the
core.

12. TRANSFORMERS AND MAINS SUPPLY
• Electricity is generated at the
power station at about
33,000V.
• A step-up transformer steps
this up to about 400,000V for
transmission in overhead cables.
• This is then stepped down for
use in homes, to 230V (or for
industrial uses, to 11,000V).

13. TRANSFORMERS AND MAINS SUPPLY
• When the potential difference is
stepped up, the current is stepped
down.
• So there is a lower current flowing
through the wires.
• This means that less energy is lost
to heat (P=I2
R)
• So more of the power supply’s
energy gets to the appliance, rather
than being lost in the wires.

14. WHAT HAPPENS WHEN YOU ARE EXPOSED TO
ELECTROMAGNETIC FIELDS?
➢ Exposure to electromagnetic fields is not a new phenomenon.
➢ However, during the 20th century, environmental exposure to man-made
electromagnetic fields has been steadily increasing as growing electricity
demand, ever-advancing technologies and changes in social behavior have
created more and more artificial sources.
➢ Everyone is exposed to a complex mix of weak electric and magnetic
fields, both
at home and at work, from the generation and transmission of electricity,
domestic appliances and industrial equipment, to telecommunications and
broadcasting.
➢ Tiny electrical currents exist in the human body due to the chemical
reactions
that occur as part of the normal bodily functions, even in the absence of
external electric fields.

15. ELECTROMAGNETIC FIELDS AT HOME
❖ Electricity is transmitted over long distances via high
voltage power lines.
❖ Transformers reduce these high voltages for local
distribution to homes and businesses.
❖ Electricity transmission and distribution facilities and
residential wiring and
appliances account for the background level of power
frequency electric and
magnetic fields in the home.
❖ In homes not located near power lines this background field
may be up to about 0.2 µT.
❖ Directly beneath power lines the fields are much stronger.
❖ House walls substantially reduce the electric field levels
from those found at similar locations outside the house.

16. NON IONISING REDIATION AND IONISING RADIATION

17. TYPICAL ELECTRIC FIELD STRENGTHS MEASURED NEAR
HOUSE HOLD APPLIANCES

18. SUMMARY OF THE ICNIRP EXPOSURE
GUIDELINES

19. ELECTROMAGNETIC AND GRAVITATIONAL
FIELDS
 Sources of electromagnetic fields consist of two
types of charge
–> positive and negative.
 This contrasts with the sources of the
gravitational field, which Are masses.
 Masses are sometimes described as gravitational
charges, the Important feature of them being that
there is only one type (no Negative masses), or,
in more colloquial terms, 'gravity is always
attractive'.

20. Electromagnetic and gravitational fields

21. REFERENCES
❑ Google Search
❑ Some Books:
1. Electromagnetic Fields (2nd Edition)
(intermediate level textbook)
2. Schaum's outline of theory and
problems of electromagnetics (2nd Edition)
(Examples and Problem Practice)

22. THANK YOU