Explanation

(b) In a constant magnetic field conducting ring oscillates with a frequency of $100\ Hz$
$i.e.,\ T = \frac{1}{100}s,\ $ in time $\frac{T}{4}$ flux links with coil changes from $BA$ to zero $\Rightarrow$ Induced emf $= \frac{change\ in\ flux}{time}$
$= \frac{BA}{T/4} = \frac{4BA}{T} = \frac{4B \times \pi r^{2}}{T} = \frac{4 \times 0.01 \times \pi \times 1^{2}}{1/100} = 2\pi V$
Induced electric field along the circle, using Maxwell equation $\oint_{}^{}{E.dl = - \frac{d\phi}{dt}} = A\frac{dB}{dt} = e$
$\Rightarrow E = \frac{1}{2\pi r} \times \left( \pi r^{2} \times \frac{dB}{dt} \right) = \frac{e}{2\pi r} = \frac{4\pi}{2\pi r} = 2V/m$