question_answer

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

A)  Zero

B)  \[Bv\pi {{r}^{2}}/2\]and P is at higher potential

C)  \[\pi rBv\]and R is at higher potential

D)  2rBv and R is at higher potential

Correct Answer: D

Solution :

 The semicircular conducting ring (PQR) can be replaced with a straight rod of length 2r. Hence motional emf induced across the rod