Current Electricity

JEE Main level, single correct, medium

302 of 380

Question 302 of 380

In a meter bridge, as shown in the figure, it is given that resistance Y=12.5ΩY=12.5 \Omega and that the balance is obtained at a distance 39.5 cm39.5 \mathrm{~cm} from end AA (by jockey J). After interchanging the resistances XX and YY, a new balance point is found at a distance l2l_2 from end AA. What are the values of XX and l2l_2 ?

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Answer: (B) 8.16Ω8.16 \Omega and 60.5 cm60.5 \mathrm{~cm}

For a balanced meter bridge,
X39.5=Y(100−39.5)⇒Y=39.5=X×(100−39.5)or…X=12.5×39.560.5=8.16Ω\begin{aligned} &\frac{\mathrm{X}}{39.5}=\frac{\mathrm{Y}}{(100-39.5)} \\ &\Rightarrow \mathrm{Y}=39.5=\mathrm{X} \times(100-39.5) \\ &or \ldots \mathrm{X}=\frac{12.5 \times 39.5}{60.5}=8.16 \Omega \end{aligned}
When X\mathrm{X} and Y\mathrm{Y} are interchanged l1l_1 and (100 −l1-l_1 ) will also interchange so, l2=60.5 cml_2=60.5 \mathrm{~cm}

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