TS EAMCET · Physics · Current Electricity
In a potentiometer experiment for the determination of the internal resistance of a cell, when an external resistance of R is connected parallel to the cell, the balancing length decreases by \(10 \%\). The internal resistance of the cell is
- A \(\frac{\mathrm{R}}{9}\)
- B \(\frac{R}{7}\)
- C \(\frac{\mathrm{R}}{5}\)
- D \(\frac{\mathrm{R}}{11}\)
Answer & Solution
Correct Answer
(A) \(\frac{\mathrm{R}}{9}\)
Step-by-step Solution
Detailed explanation
\(L_2 = L_1 - 0.1 L_1 = 0.9 L_1\) \(r = R \left( \frac{L_1}{L_2} - 1 \right) = R \left( \frac{L_1}{0.9 L_1} - 1 \right) = R \left( \frac{1}{0.9} - 1 \right) = R \left( \frac{10}{9} - \frac{9}{9} \right) = \frac{R}{9}\)
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