A thin semicircular conducting ring of radius `R` is falling with its plane verticle in a horizontal magnetic inducting `B`. At the position `MNQ`, the speed of the ring is `V` and the potential difference developed across the ring is

Options

A. 2 RBv and Q is at higher potential
B. `Bv pi R` and M is at higher potential
C. RBv and Q is at higher potential
D. Zero

Answer

A

Explanation

Induced emf depends only on the separation between two ends of wire and is independent of the shape of wire. In this case semicircular ring will be treated as rod of length 2R. Hence Bv(2R) will be the induced emf. Direction of `vec v xx vec B` is towards Q and hence point Q will be at positive potential. Hence, option (a) is correct.