Electromagnetic induction PPT Physics Class 12

 Page 1


ELECTROMAGNETIC INDUCTION
1. Magnetic Flux
2. Faraday’s Experiments
3. Faraday’s Laws of Electromagnetic Induction
4. Lenz’s Law and Law of Conservation of Energy
5. Expression for Induced emf based on both laws
6. Methods of producing induced emf
a) By changing Magnetic Field
b) By changing the Area of the Coil (Motional emf)
c) By changing the Relative Orientation of the coil with 
the Magnetic Field
7. Eddy Currents
8. Self Induction and Self Inductance
9. Mutual Induction and Mutual Inductance
10. Additional Information
Page 2


ELECTROMAGNETIC INDUCTION
1. Magnetic Flux
2. Faraday’s Experiments
3. Faraday’s Laws of Electromagnetic Induction
4. Lenz’s Law and Law of Conservation of Energy
5. Expression for Induced emf based on both laws
6. Methods of producing induced emf
a) By changing Magnetic Field
b) By changing the Area of the Coil (Motional emf)
c) By changing the Relative Orientation of the coil with 
the Magnetic Field
7. Eddy Currents
8. Self Induction and Self Inductance
9. Mutual Induction and Mutual Inductance
10. Additional Information
?
Magnetic Flux (F):
Magnetic Flux through any surface is the number of magnetic lines of force 
passing normally through that surface.
It can also be defined as the product of the area of the surface and the 
component of the magnetic field normal to that surface.
ds
n
B
B cos ?
dF = B . ds cos ?
F = B . A = B.A.n
F = B . A cos ?
Positive Flux:                                                                                                
Magnetic Flux is positive for 0° = ? < 90° & 270° < ? = 360°
Zero Flux: 
Magnetic Flux is zero for ? = 90° & ? = 270°
Negative Flux: 
Magnetic Flux is negative for 90° < ? < 270°
Direction of ds is 
along the normal to 
the surface and           
is unit normal 
vector.
n
n
dF = B . ds = B.ds.
Flux is maximum 
when ? = 0° and is
F = B . A
Page 3


ELECTROMAGNETIC INDUCTION
1. Magnetic Flux
2. Faraday’s Experiments
3. Faraday’s Laws of Electromagnetic Induction
4. Lenz’s Law and Law of Conservation of Energy
5. Expression for Induced emf based on both laws
6. Methods of producing induced emf
a) By changing Magnetic Field
b) By changing the Area of the Coil (Motional emf)
c) By changing the Relative Orientation of the coil with 
the Magnetic Field
7. Eddy Currents
8. Self Induction and Self Inductance
9. Mutual Induction and Mutual Inductance
10. Additional Information
?
Magnetic Flux (F):
Magnetic Flux through any surface is the number of magnetic lines of force 
passing normally through that surface.
It can also be defined as the product of the area of the surface and the 
component of the magnetic field normal to that surface.
ds
n
B
B cos ?
dF = B . ds cos ?
F = B . A = B.A.n
F = B . A cos ?
Positive Flux:                                                                                                
Magnetic Flux is positive for 0° = ? < 90° & 270° < ? = 360°
Zero Flux: 
Magnetic Flux is zero for ? = 90° & ? = 270°
Negative Flux: 
Magnetic Flux is negative for 90° < ? < 270°
Direction of ds is 
along the normal to 
the surface and           
is unit normal 
vector.
n
n
dF = B . ds = B.ds.
Flux is maximum 
when ? = 0° and is
F = B . A
*  Magnetic flux is a scalar quantity.
*  SI unit of magnetic flux is weber or tesla-metre
2
or ( wb or Tm
2
).
*  cgs unit of magnetic flux is maxwell.
*  1 maxwell = 10
-8
weber
*  Magnetic flux (associated normally) per unit area is called Magnetic  
Flux Density or Strength of Magnetic Field or Magnetic Induction (B).
Magnetic Flux across a coil can be changed by changing :
1) the strength of the magnetic field B
2) the area of cross section of the coil A
3) the orientation of the coil with magnetic field ? or
4) any of the combination of the above
F = B . A cos ?
Page 4


ELECTROMAGNETIC INDUCTION
1. Magnetic Flux
2. Faraday’s Experiments
3. Faraday’s Laws of Electromagnetic Induction
4. Lenz’s Law and Law of Conservation of Energy
5. Expression for Induced emf based on both laws
6. Methods of producing induced emf
a) By changing Magnetic Field
b) By changing the Area of the Coil (Motional emf)
c) By changing the Relative Orientation of the coil with 
the Magnetic Field
7. Eddy Currents
8. Self Induction and Self Inductance
9. Mutual Induction and Mutual Inductance
10. Additional Information
?
Magnetic Flux (F):
Magnetic Flux through any surface is the number of magnetic lines of force 
passing normally through that surface.
It can also be defined as the product of the area of the surface and the 
component of the magnetic field normal to that surface.
ds
n
B
B cos ?
dF = B . ds cos ?
F = B . A = B.A.n
F = B . A cos ?
Positive Flux:                                                                                                
Magnetic Flux is positive for 0° = ? < 90° & 270° < ? = 360°
Zero Flux: 
Magnetic Flux is zero for ? = 90° & ? = 270°
Negative Flux: 
Magnetic Flux is negative for 90° < ? < 270°
Direction of ds is 
along the normal to 
the surface and           
is unit normal 
vector.
n
n
dF = B . ds = B.ds.
Flux is maximum 
when ? = 0° and is
F = B . A
*  Magnetic flux is a scalar quantity.
*  SI unit of magnetic flux is weber or tesla-metre
2
or ( wb or Tm
2
).
*  cgs unit of magnetic flux is maxwell.
*  1 maxwell = 10
-8
weber
*  Magnetic flux (associated normally) per unit area is called Magnetic  
Flux Density or Strength of Magnetic Field or Magnetic Induction (B).
Magnetic Flux across a coil can be changed by changing :
1) the strength of the magnetic field B
2) the area of cross section of the coil A
3) the orientation of the coil with magnetic field ? or
4) any of the combination of the above
F = B . A cos ?
N S
Faraday’s Experiment - 1:
G
N S
G G
G
N S N S
N S N S
Page 5


ELECTROMAGNETIC INDUCTION
1. Magnetic Flux
2. Faraday’s Experiments
3. Faraday’s Laws of Electromagnetic Induction
4. Lenz’s Law and Law of Conservation of Energy
5. Expression for Induced emf based on both laws
6. Methods of producing induced emf
a) By changing Magnetic Field
b) By changing the Area of the Coil (Motional emf)
c) By changing the Relative Orientation of the coil with 
the Magnetic Field
7. Eddy Currents
8. Self Induction and Self Inductance
9. Mutual Induction and Mutual Inductance
10. Additional Information
?
Magnetic Flux (F):
Magnetic Flux through any surface is the number of magnetic lines of force 
passing normally through that surface.
It can also be defined as the product of the area of the surface and the 
component of the magnetic field normal to that surface.
ds
n
B
B cos ?
dF = B . ds cos ?
F = B . A = B.A.n
F = B . A cos ?
Positive Flux:                                                                                                
Magnetic Flux is positive for 0° = ? < 90° & 270° < ? = 360°
Zero Flux: 
Magnetic Flux is zero for ? = 90° & ? = 270°
Negative Flux: 
Magnetic Flux is negative for 90° < ? < 270°
Direction of ds is 
along the normal to 
the surface and           
is unit normal 
vector.
n
n
dF = B . ds = B.ds.
Flux is maximum 
when ? = 0° and is
F = B . A
*  Magnetic flux is a scalar quantity.
*  SI unit of magnetic flux is weber or tesla-metre
2
or ( wb or Tm
2
).
*  cgs unit of magnetic flux is maxwell.
*  1 maxwell = 10
-8
weber
*  Magnetic flux (associated normally) per unit area is called Magnetic  
Flux Density or Strength of Magnetic Field or Magnetic Induction (B).
Magnetic Flux across a coil can be changed by changing :
1) the strength of the magnetic field B
2) the area of cross section of the coil A
3) the orientation of the coil with magnetic field ? or
4) any of the combination of the above
F = B . A cos ?
N S
Faraday’s Experiment - 1:
G
N S
G G
G
N S N S
N S N S
Magnetic flux linked with the coil changes relative to the 
positions of the coil and the magnet due to the magnetic lines of 
force cutting at different angles at the same cross sectional area 
of the coil.
N S
N S
G