Two resistances are connected in two gaps of a metre bridge. The balance point is $$20$$ cm from the zero end. A resistance of $$15$$ ohm is connected in series with the smaller of the two. The null point shifts to $$40$$ cm. The value of the smaller resistance in ohm is

Question

Two resistances are connected in two gaps of a metre bridge. The balance point is $$20$$ cm from the zero end. A resistance of $$15$$ ohm is  connected in series with the smaller of the two. The null point shifts to $$40$$ cm. The value of the smaller resistance in ohm is

Infinity Learn · Accepted Answer

Let S and fi be two resistances connected in the twogaps of metre bridge and S > R. We $$haveS=100$$−$$llR=100$$−$$2020R=4R$$……….(1)When$$ $$15$$ Ω is added to resistance R, $$thenS=100$$−$$4040(R+15)=64(R+15)………(2)From$$ eqs. $$(1) and [$$2)$$, we $$get4R=64(R+15)Solving$$ , we get R $$=9$$ Ω

Two resistances are connected in two gaps of a metre bridge. The balance point is 20 cm from the zero end. A resistance of 15 ohm is connected in series with the smaller of the two. The null point shifts to 40 cm. The value of the smaller resistance in ohm is

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