Current Electricity

JEE Main level, numerical answer, medium

135 of 380

Question 135 of 380

The ratio of the equivalent resistance of the network (shown in figure) between the points aa and bb when switch is open and switch is closed is x:8x:8. The value of xx is

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Answer: 9

When switch is closed
R1=2R3+2R3=4R3{R}_{1}=\dfrac{2R}{3}+\dfrac{2R}{3}=\dfrac{4R}{3}
When open R2=3R⋅3R3R+3R=3R2{R}_{2}=\dfrac{3R\cdot 3R}{3R+3R}=\dfrac{3R}{2}
R1R2=4R3×23R=89=8x\dfrac{{R}_{1}}{{R}_{2}}=\dfrac{4R}{3}\times \dfrac{2}{3R}=\dfrac{8}{9}=\dfrac{8}{x}

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