Question

A student measures the terminal potential difference (V) of a cell (of emf $\varepsilon$ and internal resistance r) as a function of the current $(I)$ flowing through it. The slope, and intercept, of the graph between V and I, then, respectively, equal

• A. $-r$ and $\varepsilon$
• B. $r$ and $-\varepsilon$
• C. $-\varepsilon$ and $r$
• D. $\varepsilon$ and $-r$

Answer 1

Answer: (A)

$-r$ and $\varepsilon$

Answer 2

According to Ohm's law, $\frac{dV}{dl}=-r$
and $\varepsilon \,f\,I=0$ [As $V=Ir=e$]
$\therefore$ Slope of the graph $= - r$ intercept $=\varepsilon$