A thin semicircular conducting ring of radius \( R \) is falling wi...

A thin semicircular conducting ring of radius \( R \) is falling with its plane vertical in a horizontal magnetic induction \( B \). At the position \( M N Q \), the speed of the ring is \( V \) and the potential difference developed across the ring is
\[
\begin{array}{|ccccc|}
\hline \times \vec{B} & \times & \times & \times & \times \\
\times & \times & N & \times & \times \\
\times & \times & \times & \times & \times \\
\times & \times & \times V \downarrow^{\times} & \times \\
\times & \times & \times & \times & \times \\
\hline M & & \\
\hline
\end{array}
\]
(1) Zero
(2) \( B v \pi R^{2} / 2 \) and \( M \) is at higher potential
(3) \( \pi R B V \) and \( Q \) is at higher potential
(4) \( 2 R B V \) and \( Q \) is at higher potential