In an experiment of potentiometer for measuring the internal resistance of primary cell a balancing length $$\ell$$ is obtained on the potentiometer wire when the cell is open circuit. Now the cell is short circuited by a resistance $$R$$. If $$R$$ is to be equal to the internal resistance of the cell the balancing length on the potentiometer wire will be

A

$$\ell$$

B

$$2\ell$$

C

$$\ell/2$$

D

$$\ell/4$$