Current Electricity Ques 20
20. In a metre-bridge, the balancing length from the left end when standard resistance of $1 \Omega$ is in right gap is found to be $20 cm$. The value of unknown resistance is
[1999]
(a) $0.25 \Omega$
(b) $0.4 \Omega$
(c) $0.5 \Omega$
(d) $4 \Omega$
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Answer:
Correct Answer: 20.(a)
Solution:
- (a) Let unknown resistance be $X$. Then condition of Wheatstone’s bridge gives
$\frac{X}{R}=\frac{20 r}{80 r}$, where $r$ is resistance of wire per $cm$.
$\therefore X=\frac{20}{80} \times R=\frac{1}{4} \times 1=0.25 \Omega$
BETA
