Four identical cells of emf E and 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

Options

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

Answer

D

Explanation

When all cells are connected correctly , then equivalent emf of the combbination is
` E_(eq) = 4E`
and effective internal resistance of the combination is ` r_("ef" = 4r`
As one wrongly connected cell decreases the equivalent emf by 2E whereas effective internal resistance remains the same . So
`E_(eq) = 4E - 2E = 2E and r_"eff") = 4r`