Find the emf and internal resistance of a single battery which is equivalent to a combination of three batteries as show in figure.

Explanation

Battery (B) and (C) are in parallel combination with opposite polarity. So, their equivalent
`epsilon=(10/2+ -4/2)/(1/2+1/2)=(5-2)/1=3V`
`rArr r_(BC)=1Omega`
Now,
`epsilon_(BC)=6-3=3V`
`r_(ABC)=2Omega` Ans.