Course code- Applied Electromechanics
2.3 Revision of Electromagnetism
Faculty Name
name.surname@vit.edu
(An Autonomous Institute affiliated to Savitribai Phule Pune University)
BRACT’S, Vishwakarma Institute
(NBA and NAAC accredited, of Technology,
ISO 9001:2015 certified) Pune-37
(An Autonomous Institute affiliated to Savitribai Phule Pune University)
(NAAC accredited, ISO 20001:2018 certified)
Learning Outcomes
Relevant course outcome Session outcomes
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After completion of this unit, After this session, students will be
students will be able to:
able to
CO2. Distinguish and analyze
Use basic terms related to
working mechanisms of
electromagnetism.
different actuators in
Elaborate working of
electromechanical systems.
magnetic circuits in
electrical actuators.
Syllabus of Unit 2: Actuators
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Actuators: Pneumatic, Hydraulic, Electrical –
Solenoid coil, Relay, Construction, Working
principle of DC, BLDC, Stepper and Servo
motors, Merits and Demerits, applications, and
selection of actuators.
The origin of Magnetism
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Electron Spin
The number of unpaired electrons and their Clockwise or
Counter clockwise spins are mainly responsible for the
Magnetism along with the crystal structure.
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S
N
N
S
Orientation of Magnetic Flux in a material
N
Properties of Magnetic Lines of Force
1) Magnetic lines are invisible, imaginary lines which are somewhat
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elliptical in shape which never cross each other.
2) Magnetic lines are closed loops that are supposed to travel from North
pole of a bar magnet towards the South pole external to the magnet and
from South pole towards the North pole internally.
3) Magnetic lines that are parallel and travelling in the same direction,
REPEL each other.
4) Magnetic lines act like stretched rubber band which always try to
contract.
5) Magnetic lines prefer a path of minimum reluctance.
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Electromagnetism
Right Hand Thumb Rule
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Which one of the above is correct ??
Thumb is for Current or Field ??
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Cross conductor Dot conductor
Will the two conductors attract or repel ?
…. And what about this …?
Attraction or Repulsion is a property of the direction of
magnetic lines
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Cross conductor Dot conductor
The
Lines that are conductors
travelling will get
in the same repelled
direction REPEL each other
The conductors
Lines that are travelling will get
in the opposite attracted
direction ATTRACT each other
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Revision of Basic Laws of Electromagnetism
Reflection spot
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The working principle of a DC generator ,
alternator (AC generator) and transformer is
same. Do you know what is that working
principle?
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Faraday’s laws of electromagnetic induction
[The working principle of a DC generator , alternator (AC generator) and transformer]
Faraday’s laws of electromagnetic induction
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• First law • Second law
• “When the magnetic • “The magnitude of the
flux linking a emf induced in a
conductor or coil conductor or coil is
changes, an emf is directly proportional to
induced in that the rate of change of
conductor or coil.” flux linkages with it.”
E (dø/ dt)
E= -N (dø/ dt) (V)
Magnitude of emf induced
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• Magnitude:
By using Faraday’s law,
E= - N (dø/ dt) (V)
• Why negative sign?
Polarity of E.M.F. induced
• Lenz’s Law:
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“The induced current (or polarity of induced emf) in
a conductor flows in such a direction so as to
oppose the cause producing it ( e.g. movement of
magnet in above figure )”.
Working principle of a motor
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“ When a current carrying conductor is
placed in a magnetic field, it experiences a
mechanical force.”
Magnitude of force experienced
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• F= B I Lsinθ ( Newton)
• When θ=0 , F=0
• When θ= 900, F=Fmax= B I L (N)
Direction of force experienced
• Fleming’s Left Hand Rule
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“If first three fingers of left
hand held mutually
perpendicular to each
other; Forefinger showing
magnetic Field , seCond
finger showing Current ;
then thuMb indicates
direction of Mechanical
force on conductor.”
Summary
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In this session, we have discussed,
1. Basic revision of magnetism
2. Terms of electromagnetism
3. Fundamental laws governing working of electrical
actuators
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To be
next time
discussed
2.4 DC
brushed motors
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Thank You
