In a meter bridge, null point is found at a distance of 25, cm from A . If now a resistance of 10,Ω

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3.Current Electricity

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In a meter bridge, the null point is found at a distance of $25\, cm$ from $A$ . If now a resistance of $10\,\Omega $ is connected in parallel with $S$, the null point occurs at mid point of $AB$. The value of $R$ is .............. $\Omega$

A

$6.67$

B

$1.67$

C

$2.67$

D

$4.67$

Solution

Case $-$ $1$

$\frac{\mathrm{S}}{\mathrm{R}}=\frac{75}{25}\left(\frac{100-\ell}{\ell}\right)$

$\frac{S}{R}=3$

$S=3 \,R$ …….$(1)$

Case $-$ $2$

$\frac{S \times 10}{(S+10) R}=\frac{50}{50}$

$\mathrm{S} \times 10=(\mathrm{S}+10) \mathrm{R}$

$3 \mathrm{R} \times 10=(3 \mathrm{R}+10) \mathrm{R}$

$30=3 R+10$

$3 \mathrm{R}=20$

$R=\frac{20}{3}=6.67 \mathrm{\,ohm}$

Standard 12

Physics

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