2. WELCOME TO THE PHYSICS PROJECT

3. ELECTRO MAGNETIC INDUCTION

4. OBJECTIVES : IT ENABLES THE STUDENTS TO a ) DEVELOP SCIENTIFIC INTEREST b) ACQUIRE MORE KNOWLEDGE ABOUT ELECTRO MAGNETIC INDUCTION c) DEVELOP PRACTICAL SKILL

5. 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

6. 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 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.

7. 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..

8. 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.

9. 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.

10. 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.

11. 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.

12. MUTUAL INDUCTION The production of induced emf in a coil,whenever there is a change in flux in the neighbouring coil.The production of induced emf in a coil,whenever there is a change in flux in the neighbouring coil.

13. EDDY CURRENT(FOUCAULT’S CURRENT) The production of induced current in a solid metal blocks,when the flux threading through them changes.

14. ELECTRO MAGNETIC DEVICES »G»GENERATOR »T»TRANSFORMER

15. 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.

16. A.C. GENERATOR

17. 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.

18. 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

19. 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

20. TRANS FORMER A transformer consists of two coils of insulated copper wire containing different nunu 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.

21. STEP UP TRANSFORMER LOW VOLTAGE HIGH CURRENT TO HIGH VOLTAGE LOW CURRENT

22. STEP DOWN TRANS FORMER HIGH VOLTAGE LOW CURRENT TO LOW VOLTAGE HIGH CURRENT

24. 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 ?

25. OUR SINCERE THANKS TO N.V.S.

26. THE DIRECTION OF INDUCED EMF IS GIVEN BY a) FARADAY’ LAWFARADAY’ LAW b) LENZ’LAWLENZ’LAW c) BIOT-SAVART LAWBIOT-SAVART LAW

27. WHAT IS THE PRINCIPLE OF GENERATOR a) SELF INDUCTIONSELF INDUCTION b) MUTUAL INDUCTIONMUTUAL INDUCTION C) ELECTRO MAGNETIC INDUCTIONELECTRO MAGNETIC INDUCTION

28. Q 1 Q 2

29. Q 1 Q 2