CBSE Class 12-science Answered

Average induced emf = -Change in magnetic flux/time.

change in magnetic flux = final flux - initial flux = BAcosθ_f - BAcosθ_i

The initial angle is 0, since the magnetic field and area point in the same direction, but the final angle is 180 since the area vector is flipped to other side.

change in magnetic flux = final flux - initial flux = BAcos180 - BAcos0 = -2BA

Average induced emf = -2BA/time

= 2B(0.02)²/0.20 = 20x10^-3

B = 5 T.

Regards,

Team,

TopperLearning.