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)

$8r$

Answer 2

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 $r'_{series} =8r$ i.e., there is no effect on the total internal resistance of the cells