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MHT CET · Physics · Current Electricity

A cell balances against a length of 150 cm on a potentiometer wire when it is shunted by a resistance of \(5 \Omega\). But when it is shunted by a resistance of \(10 \Omega\), then balancing length increases by 25 cm . The balancing length when the cell is in an open circuit is

  1. A 200 cm
  2. B 225 cm
  3. C 210 cm
  4. D 250 cm
Verified Solution

Answer & Solution

Correct Answer

(C) 210 cm

Step-by-step Solution

Detailed explanation

\(\begin{array}{ll} & \mathrm{r}=\mathrm{s}\left(\frac{l-l_{\mathrm{b}}}{l_{\mathrm{b}}}\right) \\ \therefore \quad & 5\left(\frac{l-150}{150}\right)=10\left(\frac{l-175}{175}\right) \\ \therefore & \frac{l-150}{6}=2\left(\frac{l-175}{7}\right) \\ \therefore & 7 l-1050=12 l-2100 \\ \therefore & 5 l=1050 \\ \therefore \quad & l=210 \mathrm{~cm}\end{array}\)