FARADAYS LAWS



On changing the magnetic flux through a loop, an electromotic force (e.m.f.) i.e. induced in the loop which lasts as long as the magnetic flux keeps on changing. The magnitude of this e.m.f. is equal to the negative rate of change of flux, that is,

Induced e.m.f. = E =  
where   = N  


     = Magnetic Induction.

           = Area element.

         N = Number of turns of loop.
Thus, if the resistance of the loop is R then current through it will be given by:

Iinduced =  

    
Iinduced = -  







Direction of Induced E.M.F.



The steps to decide the direction are:



(1) Define a positive direction for the area vector  



(2) From the directions of  and the magnetic field   , determine the sign of B and its rate of change  b.



(3) Determine the sign of the induced current. If   is positive, that is, flux is inerseasing, sign of induced current is negative and ......



(4) Finally determine the direction of induced current using your right hand. Curl the fiugers of your right hand around   , with your thumb in the direction of  . If the induced current is positive, it is in the same direction as your curled fiugers and if it is negative it is in the opposite direction.