Question: Q. 6. Distinguish between emf $(E)$ and terminal voltage $(V)$ of a cell having internal resistance $r$. Draw a plot showing the variation of terminal voltage $(V) V s$. the current (I) drawn from the cell. Using this plot, how does one determine the internal resistance of the cell?
U [O.D. Comptt. I, II, III 2014]
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Solution:
Ans. Difference between emf $(E)$ and terminal voltage $(V)$
| S.No. | emf $(E)$ | Terminal voltage $(V)$ |
|---|---|---|
| (i) | It is an open circuit potential difference. |
It is a closed circuit potential difference. It is an effect. |
| (ii) | It a cause. | $\mathbf{1}$ |
(Any one) or any other relevant difference
The negative of slope gives internal resistance. $\mathbf{1}$
As per the relation $V=E-I R$, between $V$ and $I$, the emf is shown by the intercept on vertical axis. From the plot, the internal resistance is given by the line slope.
[CBSE Marking Scheme 2014]
