JEE Mains · Physics · STD 12 - 3. current electricity
In a metre-bridge when a resistance in the left gap is \(2\ \Omega\) and unknown resistance in the right gap, the balance length is found to be \(40\ \mathrm{cm}\). On shunting the unknown resistance with \(2\ \Omega\), the balance length changes by _______.
- A \(22.5 \mathrm{~cm}\)
- B \(20 \mathrm{~cm}\)
- C \(62.5 \mathrm{~cm}\)
- D \(65 \mathrm{~cm}\)
Answer & Solution
Correct Answer
(A) \(22.5 \mathrm{~cm}\)
Step-by-step Solution
Detailed explanation
First case \(\frac{2}{40}=\frac{X}{60} \Rightarrow X=3 \Omega\) In second case \(X^{\prime}=\frac{2 \times 3}{2+3}=1.2 \Omega\) \(\frac{2}{\ell}=\frac{1.2}{100-\ell}\) \(200-2 \ell=1.2 \ell\) \(\ell=\frac{200}{3.2}=62 . \mathrm{bm}\) Balance length changes by…
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