A cell of emf `E` and internal resistance r is connected across an external resistance `R`. Plot a graph showing the variation o `P.D`. Across `R`, verses 'R`.

Explanation

To solve the problem of plotting the variation of potential difference (P.D.) across an external resistance \( R \) versus \( R \) when connected to a cell of EMF \( E \) and internal resistance \( r \), we can follow these steps:

### Step 1: Understand the Circuit
We have a cell with EMF \( E \) and internal resistance \( r \) connected to an external resistance \( R \). The total resistance in the circuit is \( R + r \).

### Step 2: Write the Expression for Potential Difference
The potential difference \( V \) across the external resistance \( R \) can be expressed using Ohm's law and the formula for the total current \( I \) in the circuit:
\[
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