ELECTROMAGNETIC INDUCTION

 ELECTROMAGNETIC INDUCTION

Magnetic Flux :

Magnetic Flux through any surface is the number of magnetic lines of force passing normally through that surface.




mathematically,

magnetic flux given by dot product of strength of magnetic field B and area of surface ds. 
dΦ = B . ds

dΦ = B . ds cos θ

for a coil ,

Φ = B . A
 

Φ = B . A cos θ

 SI unit of magnetic flux is weber or tesla-metre2 or ( wb or Tm2) and cgs unit of magnetic flux is maxwell. (1 maxwell = 10-8 weber).

 Magnetic flux is a scalar quantity.

 Magnetic Flux across a coil can be changed by changing following quantities:

1)By  the strength of the magnetic field B.
2) By the area of cross section of the coil A or area of surface .
3)By the orientation of the coil with magnetic field (cos θ).

 Faraday’s Laws of Electromagnetic Induction:

 Faraday’s I Law:
Whenever there is a change in the magnetic flux linked with a circuit, an induced emf is produced and as a result  current is induced in the circuit. However, it lasts untill magnetic flux is changing.
 Faraday’s II Law:
The magnitude of the induced emf is directly proportional to the rate of change of magnetic flux linked with a circuit.
E α dΦ / dt
E = k dΦ / dt
(where k is a constant and units are chosen such that k = 1)
E = dΦ / dt
or
 E = (Φ2 – Φ1) / t