Question

Four identical cells of emf $E$ and internal resistance $r$ are to be connected in series. Suppose if one of the cell is connected wrongly, the equivalent emf and effective internal resistance of the combination is

• A. 4E and 4r
• B. 4E and 2r
• C. 2E and 4r
• D. 2E and 2r

Answer 1

Answer: (C)

Total internal resistance does not change
$\therefore R^{\prime }=4r$
Net emf is $E^{\prime }=E[n-2m]$
Here, n = total number of cells = 4
m = wrong connection = 1
$E^{\prime }=E[4-2]$
i.e. $E^{\prime }=2E$