Five identical cells each of emf 2 V and internal resistance r are connected in parallel and the combination is connected to external resistance `R = 9Omega` . If the terminal voltage across the combination is 1.5 V, find the internal resistance of each cell.

Explanation

Number of cells = n = 5
emf of each cell = 2 V
External resistance `= 9Omega`
V = 1.5
r = internal resistance of each cell.
`:.` Cells are in parallel combination
`:. 1/(r_("eff"))=1/r +1/r +1/r+1/r+1/r`
`1/(r_("eff"))= 5/r`
`r_("eff") = (E/V-1)R`
`r/5 = (2/(1.5) -1) 9`
`r/5 = 3`
`r = 15 Omega`