Two long parallel conducting horizontal rails are connected by a conducting wire at one end. A uniform magnetic field B (directed vertically downwards) exists in the region of space.

A light uniform ring of diameter d which is practically equal to separation between the rails is placed over the rails as shown in Fig. If resistance of ring be `(lambda)` per unit length
The force required to pull the ring with uniform velocity v is

Options

A. `83^(X)^(214)`
B. `84^(X)^(218)`
C. `84^(X)^(220)`
D. `87^(X)^(223)`

Answer

A

Explanation

Due to emission os `3alpha` particles, the mass number is reduced by 12 while atomic number is decresed by 6. Due to emission of `beta` particle the atomic number is increased by one while there is no change in mass number is decreased by 5. so isotope X is is `X^(214)`