Question

The diagram besides shows a circuit used in experiment to determine the emf and internal resistance of the cell $C$. A graph was plotted of the potential difference $V$ between the terminals of the cell against the current $I$, which was varied by adjusting the rheostat. The graph is shown on the right : $x$ and $y$ are the intercepts of the graph with the axes as shown. What is the internal resistance of the cell?

• A. $x$
• B. $y$
• C. $x/y$
• D. $y/x$

Answer 1

The correct option is D $y/x$

The potential difference V between the terminals of the cell is given by,
$V=E-Ir$
$\therefore r=\frac{V-E}{R}$
Hence, from graph the internal resistance of the cell is $\frac{y}{x}$