A battery is made of 12 cells having emf 5 ~V each. If three cells are unknowingly connected wrong, the resultant emf of the battery will be:

Step-by-step solution

The total number of cells is n = 12 . Each cell has an emf E = 5 V . When all cells are connected in series correctly, the total emf is nE = 12 5 = 60 V . If x cells are connected with wrong polarity, these x cells will cancel out the emf of x correctly connected cells. Effectively, the number of cells that contribute to the net emf is (n - x) minus the x cells that are opposing, which results in (n - x) - x = n - 2x effective cells. Given x = 3 cells are connected wrongly, the number of effective cells is 12 - 2(3