Two tangent galvanometers A and B are identical except in their number of turns . They are connected in seris . On passing a current through them, deflections of `60^(@)and30^(@)` are produced . The ratio of the number of turns in A and B is

Options

A. `1 : 2`
B. `2 : 1`
C. `1 : 3`
D. `3 : 1`

Answer

D

Explanation

`MB_(H)sinphi=MB_(C)sin(90^(@)-phi)` where `B_(C)=(mu_(0))/(4pi)*(2piNi)/(R)`.

i.e., `N=Ktanphi` . Where K is a constant as I is the same. Here K is not the tangent galvanoment constant as in this case it is i which is the same and N is different for the two coils .
`N_(1)ootan60^(@),N_(2)proptan30^(@)`
`therefore(N_(1))/(N_(2))=(sqrt(3))/(1//sqrt(3))=(3)/(1)`.