A  wire  88cm  long bent into a circular loop is placed  perpendicular to the magnetic field of   flux density 2.5Wb/m(sq.).  Within , 0.5s the loop  is changed  into a square of each side 22cm, and flux density  is increased to 3Wb/m(sq). Calculate the value of emf induced .                

Induced emf is given by

 

e = -d/dt  = - (₂ -₁)/t    ....(1)

 

where  = BA

 

Initially  B₁ = 2.5wb/m²

 

and A₁ = r² , where 2r =0.88 m or r = 0.88/2

 

so ₁ = B₁A₁  ....(2)

 

Also, B₂ = 3 wb/m²  

 

 A₂= (side)²  = 0.22*0.22

 

so, ₂ = B₂A₂ ......(3)

 

here t = 0.5 s .......(4)

 

Substitute (2), (3) and (4) in (1) to obtain induced emf