A galvanometer, having a resistance of $$50$$Ω, gives a full sale deflection for a current of $$0.05$$ A. The length in metre of a resistance wire of area of $$cross-section$$ $$2.97x$$ $$10-6$$ $$cm2$$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $$5$$ A current is (specific$$ resistance of the wire $$=$$ $$5$$ x $$10-7$$Ω $$m)

Question

A galvanometer, having a resistance of $$50$$Ω, gives a full sale deflection for a current of $$0.05$$ A. The length in metre of a resistance wire of area of $$cross-section$$ $$2.97x$$ $$10-6$$ $$cm2$$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $$5$$ A current is (specific$$ resistance of the wire $$=$$ $$5$$ x $$10-7$$Ω $$m)

Infinity Learn · Accepted Answer

Here $$i=G+SSigor$$ $$5=50+RR$$×$$0$$⋅$$05$$∴ $$R=(50/99)Now$$, $$R=$$ρlA  or  $$l=RA$$ρ∴ $$l=(50/99)$$×$$2.97$$×$$10$$−$$65$$×$$10$$−$$7=3m$$

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