Current Electricity Ques 80
- A resistance of $2 $ $\Omega$ is connected across one gap of a meter-bridge (the length of the wire is $100 $ $ cm$ ) and an unknown resistance, greater than $2 $ $\Omega$, is connected across the other gap. When these resistances are interchanged, the balance point shifts by $20$ $ cm$. Neglecting any corrections, the unknown resistance is
(2007, 3M)
(a) $3 $ $\Omega$
(b) $4 $ $\Omega$
(c) $5 $ $\Omega$
(d) $6 $ $\Omega$
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Answer:
Correct Answer: 80.(a)
Solution:
Formula:
- $R>2 \Omega \quad \Rightarrow \quad \therefore \quad 100-x>x$
Applying, $\quad \frac{P}{Q}=\frac{R}{S}$
We have $\quad \frac{2}{R}=\frac{x}{100-x}$ $\quad$ …….(i)
$ \frac{R}{2}=\frac{x+20}{80-x} $ $\quad$ …….(ii)
Solving Eqs. (i) and (ii), we get, $R=3 \Omega$
$\therefore$ Correct option is (a).
BETA
