Electromagnetic induction is the process of generating an electric current from a magnetic field. Michael Faraday discovered induction in 1831 through experiments showing that a current was induced in a coil of wire when a magnet was moved in and out of the coil. The magnitude of the induced current depends on factors like the strength of the magnetic field, the speed and direction of motion, and the number of turns in the coil. This principle is applied in electric generators to produce electricity.

1. Electromagnetic Induction

4. Definition
 The process of generating an electromotive force by
moving a conductor through a magnetic field is known as
electromagnetic magnetic induction.
 In simpler words we can say that production of electricity
from magnetism is called electromagnetic induction.

5. Discoverer!!!
 Michael Faraday is
generally credited with the
discovery of induction in
1831 though it may have
been anticipated by the
work of Francesco
Zantedeschi in 1829.
Around 1830 to 1832
Joseph Henry made a
similar discovery, but did
not publish his findings until
later.

7. Verifying Faraday’s Experiment
 Wind an insulated
wire over a hollow
cylinder to make a
coil.
 Connect a
galvanometer to the
coil.

8. Cont….
 Move a powerful
magnet in and out of
the coil.

9. Observation
 When the magnet is
moved in, the
galvinometer needle
deflects towards the left.
 When the magnet is
moved out, the
galvinometer needle
deflects towards the
right.

10. Cont…
 When the magnet is
stationary, the
galvanometer needle
returns to zero.

11. Result
 The deflection of the needle,
when the magnet is moved
in or out, indicates that a
current has been induced in
the coil.
 An emf is induced in the coil
due to the movement of the
magnet.
 A moving magnetic field is
necessary for
electromagnetic induction.

12. Inducing emf

13. Inducing emf using two coils
 In this case a coil is
connected to a
battery and a switch.
 Then a second coil
is taken which is
connected to the
galvanometer.

14. Cont…
 When the current is
allowed to flow in the
primary coil, a magnetic
field is generated around
it.
 The magnetic field
associated with the
second coil also
increases equally.
 This induces emf in the
secondary coil.

16. Direction of motion of the Magnet
 The direction of the
motion of the magnet
determines the
direction of the
induced current.
 The direction of the
induced emf changes
according to the
motion.

17. Orientation of the magnet
 The direction of the
induced emf changes
if the magnet is
inserted with the
reverse pole.

18. Speed of the magnet
 The speed of the
magnet determines
the strength of the
induced emf.
 Higher the speed,
higher the emf
induced.

19. Strength of the magnet
 The strength of the
magnet also
determines the
amount of emf
induced.
 The amount of emf
induced is directly
proportional to the
strength of the
magnet.

20. Number of turns in the coil
 The number of turns
in the coil also
determines the
induced emf.
 Higher the number of
turns, higher the emf
induced.

21. Faraday’s Law
 The magnitude of
induced emf, E, in
any closed circuit is
directly proportional to
the rate of change of
magnetic flux, through
the circuit.

22. Fleming’s Right Hand Rule
(The Generator rule)
 Stretch the thumb, the
forefinger and the
middlefinger of your hands
in mutuallly perpendicular
directions.
 Then the thumb represents
the motion of charge and
the forefinger and middle
finger represent the
magnetic field and the
electric current respectively.

23. Example
 Now consider a
conductor AB
connected to a
galvanometer and
placed in a magnetic
field.

24.  When we move
the conductor
downwards in the
magnetic field,
the galvanometer
needle deflects
towards left.
 This indicates
the direction of
the current in the
conductor from B
to A.

25. Electric Generators
 Generators work on
the principle of
electromagnetic
induction.
 They are used to
generate electricity.

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