ELECTROMAGNETIC
INDUCTION
PRESENTED BY:
PARAG KONWAR
ABHOY KUMAR SING
KAUSHIK PHUKAN
CONTENT
. INNTRODUCTION
• FARADAY‘S EXPERIMENT
• FARADAY’S LAW
• LENZ‘S LAW
• EDDY CURRENT
• SELF INDUCTANCE
• MUTUAL INDUCTANCE
• APPLICATION OF EMI
•
WHAT IS ELECTROMAGNETIC
INDUCTION?
• ELECTROMAGNETIC INDUCTION REFERS TO THE
GENERATION OF AN ELECTRIC CURRENT BY PASSING A
METAL WIRE THROUGH A MAGNETIC FIELD
• ELECTROMAGNETIC OR MAGNETIC INDUCTION IS THE
PRODUCTION OF AN ELECTROMOTIVE FORCE ACROSS AN
ELECTRICAL CONDUCTOR
• WHEN AN INDUCED CURRENT IS PRODUCED BECAUSE OF
VOLTAGE PRODUCTION (E.M.F) DUE TO A CHANGING
MAGNETIC FIELD, IT’S CALLED ELECTROMAGNETIC
INDUCTION
BRIEF HISTORY OF
ELECTROMAGNETIC INDUCTION
• IN 1820 , OERSTED FIRST DISCOVERED
THAT A MAGNETIC FIELD IS ALWAYS
ASSOCIATED WITH AN ELCTRIC CURRENT
• IN 1831,AUGUST 29 , FARADAY DISCOVERED
ELECTROMAGNETIC INDUCTION BY HIS FAMOUS
INDUCTION RING EXPERIMENT
FARADAY’S EXPERIMENT - 1
Observe:
i) When bar magnet was at rest, the galvanometer
showed no deflection
ii) When the bar magnet with its North Pole facing
the coil moved towards the coil, galvanometer
showed deflection, indicating flow of current in
the coil
iii) When the bar magnet with its North Pole facing
the coil moved away, galvanometer again
showed deflection but now on opposite
direction, indicating flow of current in the coil
but in opposite direction
IV) THE DEFLECTION OF THE GALVANOMETER WAS
LARGE, WHEN THE BAR MAGNET WAS MOVED FASTER
TOWARDS OR AWAY FROM THE COIL
V) WHEN THE BAR MAGNET WITH SOUTH POLE
FACING THE COIL WAS BROUGHT NEAR THE COIL, OR
WAS MOVED AWAY FROM THE COIL , THE
GALVANOMETER SHOWED DEFLECTION IN THE
OPPOSITE DIRECTION AS COMPARED TO THAT SHOWN
WITH THE SIMILAR MOVEMENTS OF THE MAGNET
MENTION IN (II) AND (III)
FARADAY’S EXPERIMENT-2
When the primary circuit is
closed current grows from zero
to maximum value. During this
period changing, current
induces changing magnetic flux
across the primary coil.This
changing magnetic flux is
linked across the secondary
coil and induces e.m.f (current)
in the secondary coil.Induced
e.m.f (current) and hence
deflection in galvanometer
lasts only as long as the
current in the primary coil and
hence the magnetic flux in the
secondary coil change.
WHEN THE PRIMARY CIRCUIT IS OPEN CURRENT
DECREASES FROM MAXIMUM VALUE TO ZERO.
DURING THIS PERIOD CHANGING CURRENT
INDUCES CHANGING MAGNETIC FLUX ACROSS THE
PRIMARY COIL.THIS CHANGING MAGNETIC FLUX IS
LINKED ACROSS THE SECONDARY COIL AND
INDUCES CURRENT (E.M.F) IN THE SECONDARY
COIL.
HOWEVER, NOTE THAT THE DIRECTION OF
CURRENT IN THE SECONDARY COIL IS REVERSED
AND HENCE THE DEFLECTION IN THE
GALVANOMETER IS OPPOSITE TO THE PREVIOUS
CASE.
FARADAY’S LAW S OF
ELECTROMAGNETIC INDUCTION
I LAW WHEN THE FLUX OF MAGNETIC
INDUCTION THROUGH A CIRCUIT IS CHANGING AN
ELECTROMAGNETIC FORCE IS INDUCED IN THE
CIRCUIT
II LAW THE MAGNITUDE OF THE EMF IS EQUAL
TO THE NEGATIVE RATE OF CHANGE OF THE
MAGNETIC FLUX
THIS EQUATION IS KNOWN AS FARADAY’S LAW OF
INDUCTION
LENZ’S LAW THE DIRECTION OF THE INDUCED EMF OR INDUCED
CURRENT IS SUCH THAT IT OPPOSES THE CHANGE THAT IS
PRODUCING IT.
I.E. IF THE CURRENT IS INDUCED DUE TO MOTION OF THE MAGNET,
THEN THE INDUCED CURRENT IN THE COIL SETS ITSELF TO STOP
THE MOTION OF THE MAGNET.
IFTHE CURRENT IS INDUCED DUE TO CHANGE IN CURRENT IN THE
PRIMARY COIL, THEN INDUCED CURRENT IS SUCH THAT IT TENDS
TO STOP THE CHANGE.
ACCORDING TO FARADAY’S LAW OF ELECTROMAGNETIC
INDUCTION, INDUCED EMF IN A CLOSED CIRCUIT IS GIVEN BY
LENZ‘S LAW EXPLAIN THE SIGNIFICANCE OF NEGATIVE SIGN.
NEGATIVE SIGN SHOWS THAT INDUCED EMF OPPOSES THE RATE OF
CHANGE OF MAGNETIC FLUX IN A CLOSED CIRCUIT. IT WAS
EXPLAINED BY LENZ
CONSIDER A BAR MAGNET MOVING TOWARDS A CLOSED
LOOP . AS THE BAR MAGNET MOVES TOWARDS THE LOOP,
THE MAGNETIC FLUX LINKED WITH THE LOOP INCREASE
WITH INCREASE IN MAGNETIC FIELD . THEN
INDUCED EMF IS SET UP IN THE CLOSED LOOP
CAUSING INDUCED CURRENT TO FLOW IN THE
LOOP, ACCORDING TO LENZ’S LAW DIRECTION
OF INDUCED CURRENT IN THE LOOP IS ANTI
CLOCK WISE. AND IF THE BAR MAGNET
IS MOVED AWAY FROM THE LOOP CURRENT IN
THE LOOP IS ANTI CLOCK
SOME APPLICATIONS OF EMI
• INDUCTION SEALING
• INDUCTION MOTORS
• ELECTRICAL GENERATORS
• TRANSFORMER
• CONTACTLESS CHARGING OF RECHARGEABLE BATTERIES
• INDUCTION WELDING
THANK YOU
