Question

A cell of emf $\epsilon$ and internal resistance $r$ is connected across a variable load resistance $R$. The graph drawn between its terminal voltage and resistance $R$ is

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

According to the question, circuit diagram of a cell is given below,

As, $Ir=E-V$
$\Rightarrow \frac{V}{R}r=E-V$
$\Rightarrow V\left[1+\frac{r}{R}\right]=E$
$\Rightarrow V=\frac{E}{R+r}\cdot R$
General equation of a straight line passing through the origin,
$y=mx$
Here, $y=V,m=\frac{E}{R+r}=$ slope of the line
and $x=R$
As this line is passing through the origin and has a slope which reduces as $R$ increases. Hence, the graph is