Q77 / 120 · NEET 2012 (Mains) · Physics

A cell having an $\operatorname{emf} \varepsilon$ and internal resistance $r$ is connected across a variable external resistance $R$. As the resistance $R$ is increased, the plot of potential difference $V$ across $R$ is given by

  • A
    Figure
  • B
    Figure
  • Correct answer
    C
    Figure
  • D
    Figure

Solution

Here, $E=I(R+r) \Rightarrow E=I R+I r$ and $$ \begin{aligned} & E=V+I r \\ & E=V+\frac{E r}{R+r} \\ & V=E-\frac{E}{R+r} \times r \\ & y=c-\frac{1}{x} \end{aligned} $$ This equation represents option (3).

Hence, the correct answer is option: 'C'.

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