Five cells each of emf E and internal resistance r send the same amount of current through an external resistance R whether the cells are connected in parallel or in series. Then the ratio ( R r ) is

Step-by-step solution

Given : Number of cells, n=5 , emf of each cell =E Internal resistance of each cell =r In series, current through resistance RI= n E n r+R = 5 E 5 r+R In parallel, current through resistance RI^ = E r n +R = n E r+n R = 5 E r+5 R According to question, I=I^ 5 E 5 r+5 R = 5 E r+5 R 5 r+R=r+5 R or R=r R r =1