A moving coil galvanometer of resistance `100Omega` shows full scale deflection when a current of `100muA` passes through it. If is intended to show full scle deflection when a current of 1mA passes through it the value of shunt resistance in ohm to be connected to the galvanometer is

Options

A. `(9)/(4)`
B. `(10)/(3)`
C. `(100)/(9)`
D. `(900)/(7)`

Answer

C

Explanation

Equivalent resistance of each piece ,` R' = (R)/(20)`
10 pieces are joined I sereies , `R_e= R'_1+R'_2+….+R'_10`
`R_S= 10R'`
10 Pieces are joined in parallel ,
`(1)/(R_e) = (1)/(R'_1)+(1)/(R'_2+….+(1)/(R'_10)`
`(1)/(R_e) = (10)/(R')`
`Rightarrow R_p = R'/10`
`R_S` and `R_P` are connected in series
Reffective `= 10R'+ (R')/(10) = 10(R/10)+ (R)/(200) = (101R)/(200)`