CBSE Class 12-science Answered

. E.M.F of each cell, E = 2.0 V
Terminal voltage of cell, V = 1.5 V
Let r' be the internal resistance of each cell. As the two cells are connected in parallel, so the total internal resistance say 'r' of the cells is given by
r = (r'/2)
Total external resistance R is given by
R = 4ohms
Using equation for internal resistance
r = [(E - V)/V]R
We have, r = [(2.0 - 1.5)/1.5]4 = (0.5/1.5)4 ohm = (4/3) ohms
So, internal resistance of each cell,
r' = 2r = (4 x 2)/3 = (8/3) = 2.666 ohm