The deflection in galvanometer falls to `((1)/(4))^(th)` when it is shunted by `3Omega`. If additional shunt of `2Omega`is connected to earlier shunt in parallel, the deflection in galvanometer falls to

Options

A. `(1)/(2)`
B. `((1)/(3))^(rd)`
C. `((1)/(4))^(th)`
D. `((1)/(8.5))^(th)`

Answer

D

Explanation

In galvanometer,
`(l_(g))/(l)=(S)/(S+G)`
where, S is shunt resistance, G is resistance of galvanometer,
`rArr" "(1)/(4)=(3)/(3+G)`
`or" "G=9Omega`
In new condition,
`(l_(g))/(l)=((6)/(5))/((6)/(5)+9)`
`["Effective shunt resistance "=(3xx2)/(3+2)=(6)/(5)Omega]`
`=((1)/(8.5))^(th)`