A long slenoid of radius 2 cm has 100 turns/cm and carries a current of 5A. A coil of radius 1 cm having 100 turns and a total resistance of 20 `Omega` is placed inside the solenoid coaxially. The coil is connected to a galvanometer. If the current in the solenoid is reversed in direction, find the charge flown through the galvanometer.

Options

A. `2xx10^(-4)C`
B. `3xx10^(-4)C`
C. `2xx10^(-5)C`
D. `4xx10^(-4)C`

Answer

A

Explanation

`phi_(1)=NBAcos0=NBA`
`phi_(2)=NBAcos180^(@)=-NBA`
`|Deltaphi|=phi_(2)-phi_(1)=2NBA`
`Deltaq=(|Deltaphi|)/(R)=(2NBA)/(R)=(2N(mu_(0)ni)A)/(R)`
`=2xx100(4pixx10^(-7)xx100xx10^(2)xx5)(pixx10^(-4))/(20)`
`=2xx10^(-4)C`