A thin semicircuilar conducting ring (PQR) of radius `r` is falling with its plane vertical in a horizontal magnetic field B, as shown in Fig. The potential difference developed across the ring when its speed is `upsilon`, is

Options

A. zero
B. `B upsilon pi r^(2)` and P is at higher potential
C. `pi r B upsilon` and R is at higher potential
D. `2 r B upsilon` and R is at higher potential

Answer

D

Explanation

Induced emf `e = B L_(eff^(upsilon))`
Here, `L_(eff)` = diameter of ring = 2 r
`:.e = b 2 r upsilon`
Here, R will be at higer potential. Thus, option (d) is ture.