કુલ \({\text{e}}{\text{.m}}{\text{.f }}{{\text{E}}_{{\text{eq}}}}{\text{  =  2V}}\)

કુલ બાહ્ય અવરોધ \(R\,\, = \,\,\frac{{15\,\, \times \,\,15}}{{15\,\, + \;15}}\,\, = \,\,\frac{{15}}{2}\,\, = \,\,7.5\,\,\Omega  \)

સમતુલ્ય કોષમાથી વહેતો વિધુતપ્રવાહ \(\,\,I\,\, = \) (ટર્મિનલ વોલ્ટેજ) / (બાહ્ય અવરોધ)

\(\,\, = \,\,\frac{{1.6}}{{7.5}}\,\,A\)

\(\because \,\,E\,\, - \,\,I\,\,\left( {\frac{r}{4}} \right)\,\, = \,\,1.6\)

\(\,\therefore \,\,2\,\, - \,\,\frac{{1.6}}{{7.5}}\,\,\left( {\frac{r}{4}} \right)\,\, = \,\,1.6\)

\(\, \Rightarrow \,\,r\,\, = \,\,7.5\,\,\Omega \)