Question

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

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

Answer 1

The correct option is A

2E and 4r

Total internal resistance does not change.

$\therefore R^{‘}=4r$

$E^{\prime }=E[n–2m]$ n = Total number of cells, m = Wrong connection

$E^{\prime }=E[4–2]=2E$