The graph shows potential difference $V$ across terminals of a cell...

Question

The graph shows potential difference $V$ across terminals of a cell against load current $I$. How do you find emf and internal resistance from this graph?

Accepted Answer

From $V = E - Ir$, the $V$-$I$ graph is a straight line.
- emf $E$ = y-intercept (value of $V$ when $I = 0$)
- Internal resistance:
$$r = \left|\frac{\Delta V}{\Delta I}ight| = |	ext{slope}|$$
- Short-circuit current = x-intercept $= E/r$

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