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(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 ? |
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Answer» Solution :(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))` |
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