∴ Seven identical cells each of emfE and internal resistance r are connected as shown in the figure below.
∵ VAB=E−Ir ........(i) Applying KVL in the loop, −E+Ir−E+Ir−E+Ir−E +Ir−E+Ir−E+Ir−E+Ir=0 ⇒E=Ir .......(ii) From Eqs. (i) and (ii), we get VAB=Ir−Ir=0