Question

A cell emf of (E) and internal resistance (r) is connected across a variable load resistance (R). Draw plots showing the variation of terminal voltage V with

(i) R 

(ii) the current (I) in the load

Answer 1

The given situation is shown in figure

VA – VB = V \(\Rightarrow\) Terminal voltage of the battery

\(I = \frac{E}{R+ r} \) ...(i)

(I) Variation of V with R

\(V= E- Ir \Rightarrow V = E - \left(\frac{E}{R+r}\right) r\)

\(V= \frac{ER}{r +R}\) 

(II) Variation of V with I

V = E – Ir