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## Electromagnetic Induction-ppt-N.V.V.S.Murty

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### Electromagnetic Induction-Faraday's laws-Lenz's law-Self and Mutual Induction. – PowerPoint PPT presentation

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Title: Electromagnetic Induction-ppt-N.V.V.S.Murty

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Power point presentation By
• NEMANI.V.V.S.N.MURTY, M.Sc.,
• Lecturer in Physics
• S.K.B.R.College , AMALAPURAM
• E-mail vvsmnemani_at_gmail.com

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Topic
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ELECTROMAGNETIC INDUCTION
The phenomenon of inducing a current by changing
the magnetic field in a coil of wire is known
as ELECTROMAGNETIC INDUCTION.
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(No Transcript)
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If a magnetic field is applied to a surface of
area A, and the component of that magnetic field
that is perpendicular to the surface is B, then
the flux is given by the expression
Magnetic flux
The SI unit of magnetic flux is the WEBER, Wb.
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• Induced EMF
• Almost 200 years ago, Faraday looked for
evidence that a magnetic field would induce an
electric current with this apparatus

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Induced EMF
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• He found no evidence when the current was
steady but did see a current induced when the
switch was turned on or off.

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• Induction
• 1. "When the magnetic flux linked with a circuit
is changed, an induced EMF is set up in the
circuit.
• 2. "The magnitude of the induced emf in a coil is
the negative of the rate of change in magnetic
flux through that coil multiplied by the number
of turns in that coil.
• So, for a coil with N turns
• the average induced emf will be

(1791- 1867) England
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Lenz's law
Lenz's law enables us to determine the direction
of the induced current The direction of the
induced current is such as to oppose the change
that causing it.
Russian physicist who in 1833 formulated Lenz's
law
The above diagram shows the north pole of a bar
magnet approaching a solenoid. According to
Lenz's law, the current which is thereby
generated in the coil must cause an effect which
opposes the approaching magnetic field.
This diagram shows the north pole of a bar magnet
withdrawing from a solenoid. According to Lenz's
law, the current which is thereby generated in
the coil must cause an effect which opposes the
departing magnetic field.
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Self Induction
When a current passes through a coil of wire is
changed an Induced EMF is set up in the coil.
This Phenomenon is called Self Induction. Magneti
c flux Ø Li , where L is the coeff. of self
Induction and Induced EMF e -L di/dt
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• A solenoid is a long wire wound as a helix
to produce a reasonably uniform magnetic field B
in the interior of the solenoid coils when the
solenoid carries a steady current I.
• When the coils (turns) are closely spaced,
each turn can be approximated as a circular loop
and the net magnetic field B is the vector sum of
the fields resulting from all of the turns.
• Magnetic field B µoni
• Magnetic flux Ø BA µoniA
• Flux through N turns µoniAN µon2 iAl
• Where N nl
• Self Inductance L µon2 Al

solenoid
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Mutual Induction
When a current passes through a primary coil an
Induced EMF is developed in the secondary coil.
This phenomenon is called Mutual Induction.
Magnetic flux Ø Mi , where M is the coeff. of
Mutual Induction and Induced EMF e - M di/dt
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Experimental arrangement for Mutual Induction
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Henry
• Henry is the unit used for both Coefficient
of self Induction and Coefficient of Mutual
Induction.
• Henry is the bigger unit and hence two
smaller units were introduced. They are milli
henry (mH) and micro henry(µH).
• 1 mH 10-3 henry and
• 1 µH 10-6 henry

Joseph Henry (1797-1878) American
scientist
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If there are any suggestions or comments feel
free to write to my mail in the first slide
Thank you all