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 In a potentiometer experiment, the balancing length of a cell is 560 cm. When an external resistance of 10 Ω is connected in parallel to the cell, the balancing length changes by 60 cm. The internal resistance of a cell is 

Answer:

Explanation:

 Let us consider a cell of emf E and balancing length l₁

 E=kl₁

 potential difference is balanced by length  l₂ , V= kl₂

 $r= \left(\frac{E-V}{V}\right)R= \left(\frac{E}{V}-1\right)R= \left(\frac{l_{1}}{l_{2}}-1\right)R$

 $r= \left(\frac{560}{560-60}-1\right)10= \left(\frac{56}{50}-1\right)10= \frac{6}{5}=1.2 $ Ω