(a) Define current sensitivity of a galvanometer. Write its expression.
(b) A galvanometer has resistance and shows full scale deflection for currently `I_(g)`.
(i) How can it be converted into an ammeter to measure current up to `I_(0) (I_(0) gt I_(g))`
(ii) What is the effective resistance of this ammeter ?

Explanation

(a) Current sensitivity of a galvanometer is defined as deflection per unit current flowing through it.
Current sensitivity `=phi/I=(NAB)/(k)`
(b) A galvanometer of resistance G and full scale deflection current `I_g` can be converted into an ammeter of range `l_(0)` by joining a shunt resistance `r_(s)` in parallel to galvanometer, where
`r_(s)=(I_(g))/(I-I_(g)) .G`
(ii) The effective resistance of the ammeter is `(G.r_(s))/(G+r_(s))`