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Question
A variable resistor R is connected across a cell of emf ε and internal resistance r as shown in the figure. Draw a plot showing the variation of
(i) Terminal voltage V and
(ii) the current I, as a function of R.
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Solution
(i) Terminal voltage across a cell as a function of R
As resistance R increases current (I) in the circuit decreases and terminal voltage (V) increases.
We know V = ε –Ir; Where ε is emf of the cell
(ii) Current I as a function of R.
The current across a cell is given by `"I" = epsilon/("R"+"r")`
When R increases I decreases
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