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
`epsi_(BC)=(10/2+(-4)/2)/(1/2+1/2)=(5-2)/1=3VrArrr_(BC)=1 Omega.`

Now, `epsi_(ABC)=6-3=3V`
`r_(ABC)=2Omega`