Two cells of emfs E1 and E2 and internal resistances r1 and r2 when connected in series and across an external resistance R give a current of 2A. When the polarity of one of the cells is reversed, the current through R is 1A. The ratio E1/E2 =
3
We have,
2=E1+E2R+r1+r2And 1=E1+E2R+r1+r2⇒2(E1−E2)=E1+E2E1=3E2E1E2=3