A galvanometer, having a resistance of $$50$$ Ω gives a full scale deflection for a current of $$0.05$$ A. The length in metre of a resistance wire of area of $$cross-section$$ $$2.97x$$ $$10-2$$ $$cm2$$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $$5$$ A current is (specific$$ resistance of wire $$=$$ $$5$$ x $$10-7$$ Ω$$m)

Question

A galvanometer, having a resistance of $$50$$ Ω gives a full scale deflection for a current of $$0.05$$ A. The length in metre of a resistance wire of area of $$cross-section$$ $$2.97x$$ $$10-2$$ $$cm2$$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $$5$$ A current is (specific$$ resistance of wire $$=$$ $$5$$ x $$10-7$$ Ω$$m)

Infinity Learn · Accepted Answer

We know that i−$$igS=igG$$∴ $$i=(G+S)SigTherefore$$ $$5=50+RR$$×$$0$$⋅$$05or$$ $$R=2$$⋅$$54$$⋅$$95Further$$ $$R=$$ρlA  or  $$l=AR$$ρor $$l=2$$⋅$$97$$×$$10$$−$$6$$×$$(2$$⋅$$5)5$$×$$10$$−$$7$$×$$4$$⋅$$95=3m$$

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