NEET Class neet Answered

By Faraday's law of induction, we get Induced EMF  E = - ( dΦ / dt )

where Φ = B × A , is flux of magnetic field , B is magnetic field induction and A is area of loop .

When the shape of loop chages from square to circle change in area gives induced EMF .

Square loop area A_s = 0.22 × 0.22  m² . = 4.840 × 10^-2 m²

Circumference of circular loop = circumference of square loop

Let R be the radius of circular loop

2π R = 0.22 × 4 m = 0.88 m

R = 0.88 / (2π) m = 0.14 m

Area of circular loop = π (0.14)² = 6.162 × 10^-2 m² 

Induced EMF E = - ( dΦ / dt ) = -d/dt (  B × A ) = - B × (dA/dt) .

E = -  { 0.2 × [ 6.162 - 4.840 ] × 10^-2 } / 0.4  V = - 6.61 × 10^-3 V