Question

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 60cm. The internal resistance of the cell in ohms is

• A. 1.6
• B. 1.4
• C. 1.2
• D. 0.12

Answer 1

Answer: (C)

1.2

$\Rightarrow r=R(\frac{l_1}{l_2}-1)$
$=10(\frac{560}{500}-1)=10\times 0.12=1.2\Omega$