Question

For a cell, the graph between the potential difference V across the terminals of the cell and the current I drawn from the cell is shown in figure. The emf and the internal resistance of the cell are-

• A. 2v,0 4$\Omega$
• B. 2v,0,5$\Omega$
• C. >2v,0,4$\Omega$
• D. <2v,0,4$\Omega$

Answer 1

The correct option is A 2v,0 4$\Omega$

$Given:$ Graph is given above.

$Solution:$ As we know that, the emf of a cell having internal

resistance $r$ is given by

$V=E-Ir$

Where,

$V=$ potential difference

$E=e.m.f$

I=current

$r=$ internal resistance

Now, we put values from graph in the above

equation in order to find emf of cell and resistance

Take $V=2V$ and $I=0$ from the graph

$V=E-Ir$

On putting the values we get

$2=E-\left(0\right)r$

On solving we get

$E=2V$

Here, the current is zero so the maximum potential

difference is equals to emf. So, the value of emf is

$2V$.

Now, put $V=0,E=2V$ and $I=5A$ in the formula of emf

of cell we have

$V=E-Ir$

$0=2-5r$

$r=\frac{2}{5}=0.4\Omega$

So, the value of $E=2V$ and $r=0.4\Omega$

$So,the$ $correct$ $option:A$