Current Electricity - Result Question 97

102. The resistances in the two arms of the meter bridge are $5 \Omega$ and $R \Omega$, respectively. When the resistance $R$ is shunted with an equal resistance, the new balance point is at $1.6 l_1$. The resistance ’ $R$ ’ is :

[2014]

(a) $10 \Omega$

(b) $15 \Omega$

(c) $20 \Omega$

(d) $25 \Omega$

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Answer:

Correct Answer: 102. (b)

Solution:

  1. (b) This is a balanced wheatstone bridge condition,

$\frac{5}{R}=\frac{\ell_1}{100-\ell_1}$ and $\frac{5}{R / 2}=\frac{1.6 \ell_1}{100-1.6 \ell_1}$

$\Rightarrow R=15 \Omega$