Transcript mutual induction

ELECTRO MAGNETIC INDUCTION
OBJECTIVES :
• IT ENABLES THE STUDENTS TO
• a ) DEVELOP SCIENTIFIC INTEREST
• b) ACQUIRE MORE KNOWLEDGE
•
ABOUT ELECTRO MAGNETIC
•
INDUCTION
• c) DEVELOP PRACTICAL SKILL
ELECTRICITY !
Imagine a world where there is No ELECTRICITY
!
No lights , No trains , No personal computers.
The pioneering experiments of FARADAY & HENRY have
lead
Directly to development of modern day generators &
transformers .
Civilisation as it exists today owes a great deal to the
discovery
Of ELECTRO MAGNETIC INDUCTION
INTRODUCTION

The experiments of
Michael Faraday in
England and of Joseph
Henry in U S A
.conducted around 1830
demonstrated
conclusively that the
changing magnetic field
produces Electrical
fields and Electric
currents .
THE EXPERIMENT OF FARADAY
&HENRY
• When a bar magnet is
pushed towards the coil
the galvanometer
deflects.This remarkable
fact implies that a current
has been set up in the coil
in the absence of a battery.
The deflection stops when
the magnet is made
stationary and reverses
while the magnet is being
pulled away from the coil
• This experiment works just
as well when the coil is
moved towards the
magnet. .
ELECRO MAGNETIC
INDUCTION
 It
is the phenomenon
of production of
induced emf in a coil
whenever there is a
change in flux linked
with the coil changes
.
LAWS OF ELECTROMAGNETIC
INDUCTION
• 1)Whenever magnetic flux passing
through a circuit changes ,an
induced emf is produced whose
magnitude is equal to rate of
change of magnetic flux,and it lasts
as long as there is a change in flux .
• 2) The direction of the induced emf
is such that it always opposes the
cause which produces it .
•
d
E 
dt
ENERGY CONSERVATION
_ELECTRO MAGNETIC INDUCTION
As the current starts flowing in the coil in one direction,the increase in
magnetic flux induces an opposite current in the ring, The magnetic field set
up by the induced current in the ring opposes the field of the coil & the
repulsion between the like poles throws the ring upwards . When the
current in the coil reverses its direction , the induced current in the ring aiso
reverses ,& again there is a repulsion .
Self induction
• The phenomenon
of production
induced emf in a
circuit due to
change of current
in the circuit it self
is called self
induction .
MUTUAL INDUCTION
• The production of
induced emf in a coil
,whenever there is a
change in flux in the
neighbouring coil .
EDDY CURRENT(FOUCAULT’S
CURRENT)

The production
of induced
current in a
solid metal
blocks ,when
the flux
threading
through them
changes .
ELECTRO MAGNETIC
DEVICES
»GENERATOR
»TRANSFORMER
A.C.GENERATOR
• It is a device which converts
mechanical energy in to electrical
energy .
• PRINCIPLE :Electro magnetic
induction
• Direction of induced current :
Fleming’s Right hand rule.
A.C. GENERATOR
FLEMING ‘S RIGHT
HAND RULE
• Stretch the thumb , fore
finger and middle finger of
your right hand such that
they are perpendicular to
each other ,if the thumb
represents the direction of
motion of the coil ,fore
finger represents direction
of magnetic field then the
middle finger represents
direction of the induced
current .
THEORY
• Let ‘N’ be the number of turns of the
coil,
• ‘B’ be the strength of the magnetic
field,
• ‘A’ be the area of the coil ,
• Then flux associated with the coil =
N B.A
=NBACOS
=NBACOSt
• Induced emf
=d/dt NBACOSt
BA  NSIN  t
TRANS FORMER
It isan electrical device which convert
• High voltage Low current to Low
voltage High current & viceversa .
• PRINCIPLE :Electro magnetic
induction(MUTUAL INDUCTION)
• Types of trans former : 1)step up
•
2)step down
n
u
TRANS FORMER
 A transformer consists of two
coils of insulated copper wire
containing different
Number of turns wound on a soft iron core . The coil to
which electrical energy is fed is called primary and the coil
from which the energy is drawn is called secondary .The
entire magnetic flux coming out of the primary coil due to
the current in it remains confined practically within the iron
core and hence passes fully through the secondary.
STEP UP
TRANSFORMER
• LOW VOLTAGE
HIGH CURRENT TO
HIGH VOLTAGE
LOW CURRENT
STEP DOWN TRANS FORMER
HIGH VOLTAGE LOW CURRENT TO LOW
VOLTAGE HIGH CURRENT
TEST YOUR KNOWLEDGE
1)What is electromagnetic induction ?
2) State the laws of electro magnetic induction ?
3)What is the principle of trans former ? What
are the two types of transformer ?
4)What are eddy currents ? Write any three
applications ?
5)With the help of neat diagram explain the
principle,construction and working of an
a.c.generator ?
OUR SINCERE THANKS
TO
N.V.S.
• THE DIRECTION OF INDUCED EMF IS
GIVEN BY
• a) FARADAY’ LAW
• b) LENZ’LAW
• c) BIOT-SAVART LAW
• WHAT IS THE PRINCIPLE OF
GENERATOR
• a) SELF INDUCTION
• b) MUTUAL INDUCTION
• C) ELECTRO MAGNETIC INDUCTION
Q1
Q2
Q1
Q2