Two cells of emf 2V and 4V and internal resistance `1Omega` and `2Omega` respectively are connected in parallel so as to send the current in the same direction through an external resistance of `10Omega`. Find the potential difference across `10Omega` resistor.

Explanation

Given `E_(1)=2V,r_(1)=1Omega`
`E_(2)=4V,r_(2)=2Omega`
We know that `E_("eq")=(E_(1)r_(2)+E_(2)r_(1))/(r_(1)+r_(2))`
i.e. `E_("eq")=(2xx2+4xx1)/(1+2)=(8/3)` volt
and `r_("eq")=(r_(1)r_(2))/(r_(1)+r_(2))=(1xx2)/(1+2)=(2/3)Omega`
Terminal pd=`((E_("eq"))/(R+r_("eq")))R`
`=(8/3)/((10+2/3))xx10` volt
Terminal Pd = 2.5 V.