A square loop of side 22 cm is changed to a circle in time 0.4 s. The magnetic field present is 0.27 T. Find the average emf induced in the circular loop?
Area of square loop = 484 cm^2 and 22x4 = length of square = length of circle= 2pi r. Hence find r and you got the change in area in 0.01 s. 0.27 T is B per unit area. Change area in m^2. Now change in area x B/ total time taken = E induced. As Eind= d phi/dt and phi = B.A so B is constant and A is changing