A potentiometer wire is 100 cm long and a constant
potential difference is maintained across it. Two
cells are connected in series first to support one
another and then in opposite direction. The balance
points are obtained at 50 cm and 10 cm from the
positive end of the wire in the two cases. The ratio
of emf's is :-
(1) 5 : 1
(2) 5 : 4
(3) 3 : 4
(4) 3 : 2