Question

$8$ identical cells, each of emf $E$ and internal resistance $r$, are connected in series. If polarity of two cells is reversed then the total internal resistance in the circuit will be

• A. $8r$
• B. $6r$
• C. $4r$
• D. $2r$

Answer 1

Answer: (A)

Here, emf of each cell $=E$
Internal resistance of each cell $=r$
Total internal resistance of $8$ cells are connected in series is
$r_{series}=8r$
If the polarity of two cells are reversed, then the total internal resistance of the cells is
$r_{series}^{\prime }=8r$
i.e., there is no effect on the total internal resistance of the cells