JEE PYQ: Current Electricity Question 30
Question 30 - 2020 (07 Jan 2020 Shift 2)
The balancing length for a cell is 560 cm in a potentiometer experiment. When an external resistance of $10,\Omega$ is connected in parallel to the cell, the balancing length changes by 60 cm. If the internal resistance of the cell is $\frac{N}{10},\Omega$, where N is an integer then value of N is ____.
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Answer: 12
Solution
$E \propto l$ so $E = k(560)$. When external resistance connected: $\frac{E}{r+10} \times 10 = k(500)$. Dividing: $\frac{r+10}{10} = \frac{56}{50}$. $50r + 500 = 560$. $r = \frac{60}{50} = \frac{6}{5} = \frac{12}{10},\Omega$. $N = 12$.
BETA
