A galvanometer of resistance `G` is shunted by a resistance `S` `ohm`. To keep the main current in the circuit uncharged, the resistance to be put in series with the galvanometer

Options

A. `(G^(2))/((S+G))`
B. `(SG)/((S+G))`
C. `(S^(2))/((S+G))`
D. `(G)/((S+G))`

Answer

A

Explanation

Refer to keep the current `I` in the circuit unchanged, a resistance R is connected in series of shunted galvanometer, figure (b). It will be so if

`G=(GS)/(G+S)+R`
or `R=G-(GS)/(G+S)=(G^(2))/(G+S)`