Two cells of unequal emfs, ℰ1 and ℰ2, and internal resistances r1 and r2 are joined as shown. VA and VB are the potentials at A and B respectively.
(a) One cell will continuously supply energy to the other.
(b) The potential difference across both the cells will be equal.
(c) The potential difference across one cell will be greater than its emf.
(d) VA - VB = ℰ1r2 + ℰ2r1 / (r1 + r2).