(i) Current in circuit \(I=\frac{\epsilon}{R+r}\)
Terminal potential difference
\(V=IR=(\frac{\epsilon}{R+r})R\)
= \(\frac{\epsilon}{(R+r)/R}=\frac{\epsilon}{1+\frac{r}{R}}\)
When R increases r/R decreases, so terminal potential difference increases with the increase of R.
When R = 0, V → 0
When R = r, V = \(\frac{\epsilon}{2}\)
When R → ∞ (open circuit), V = ε
The graph of terminal potential difference V versus R is shown in figure.
(ii) V = E - Ir \(\Rightarrow I=\frac{E\,-\,V}{r}\)
