AIPMT 2010 Physics and Chemistry Paper

Here,
Magnetic field B=0.025T
Radius of the loop, r=2‌cm=2×10−2m
Constant rate at which radius of the loop shrinks
‌

dr

dt

=1×10−3ms−1
Magnetic flux linked with the loop is
φ=BA‌cos‌θ=B(πr2)‌cos‌0∘=Bπr2
The magnitude of the induced emf is
|ε|=‌

dφ

dt

=‌

d

dt

(Bπr2)=Bπ2r‌

dr

dt

=0.025×π×2×2×10−2×1×10−3
=π×10−6V=πµV