A galvanometer of resistance `50Omega` is connected to a battery of 3V along with a resistance of `2950Omega` in series. A full scale deflection of 30 division is obtained in the galvanometer. In order to reduce this deflection to 20 division, the resistance in series should be:-

Options

A. `2a = b`
B. `3a = 2b`
C. `a = 2b`
D. `a = b`

Answer

A

Explanation

`x_(cm) = (int xdm)/(int dm)`
`rArr (7L)/(12) = (int_(0)^(L)x(a + (bx)/(L)) dx)/(int_(0)^(L) (a + (bx)/(L)) dx)`
Solving we get `2a = b`