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(FOUCAULTS 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 : Flemings 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 Induced emf BA NSIN t
=NBACOS =NBACOSt =d/dt NBACOSt 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) LENZLAW c) BIOT-SAVART LAW WHAT IS THE PRINCIPLE OF GENERATOR a) SELF INDUCTION b) MUTUAL INDUCTION C) ELECTRO MAGNETIC INDUCTION Q1
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