Two concentric and coplanar coils have redii a and `b ( gt gt a)` as shows in Fig. Resistance of the inner coil is `R`. Current in the outer coil in increased from `0` to `i`, then the total charge circulating the inner coil is

Options

A. `(mu_(0)ia^(2)pi)/(2Rb)`
B. `(mu_(0)iab)/(2R)`
C. `(mu_(0)iab)/(2a) (pib^(2))/(R )`
D. `(mu_(0)ib)/(2piR)`

Answer

A

Explanation

`Deltaq = (Delta phi)/(R )`
`phi_(i) = 0`
`phi_(f) = (mu_(0)/(2) (i)/(b)) (pia^(2)) = (mu_(0)ia^(2)pi)/(2b)`
`:. Delta phi = phi_(f) - phi_(i) = (mu_(0)ia^(2)pi)/(2b)`
So, `Deltaq = (mu_(0)ia^(2)pi)/(2Rb)`