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3.Current Electricity
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A resistance of $2 \Omega$ is comnected across one gap of a metre-bridge (the length of the wire is $100 \mathrm{~cm}$ ) and an unknown resistance, greater than $2 \Omega$, is connected across the other gap. When these resistance are interchanged, the balance point shifts by $20 \mathrm{~cm}$. Neglecting any corrections, the unknown resistance is
A
$3 \Omega$
B
$4 \Omega$
C
$5 \Omega$
D
$6 \Omega$
(IIT-2007)
Solution
$ \frac{2}{\mathrm{x}}=\frac{\ell}{100-\ell} $ ……………$(I)$
$ \frac{\mathrm{x}}{2}=\frac{\ell+20}{80-\ell}$ ……………$(II)$
Solving $(i)$ and $(ii)$ $x=3 \Omega$
Standard 12
Physics
Similar Questions
A student obtained following observations in an experiment of meter bridge to find the unknown resistance of the circuit The most accurate value of unknown resistance is ………… $\Omega$
| S.No. | $R$ | $l$ | $100-l$ | $S = \left( {\frac{{100 – l}}{l}} \right)R$ |
| $1$ | $20\,\Omega $ | $43$ | $57$ | $26.51\,\Omega $ |
| $2$ | $30\,\Omega $ | $51$ | $49$ | $28.82\,\Omega $ |
| $3$ | $40\,\Omega $ | $59$ | $41$ | $27.80\,\Omega $ |
| $4$ | $60\,\Omega $ | $70$ | $30$ | $25.71\,\Omega $ |
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