Which of the following graphs for a cell correctly shows the relation between the terminal potential difference (V) and current (I) flowing through it.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1)
The terminal potential difference of a cell of emf \( E \) and internal resistance \( r \) depends on the direction of the current through it. When the current is driven into the cell (the cell is being charged), the potential drop \( Ir \) across the internal resistance adds to the emf.
\( V = E + Ir \)
This is a straight line with positive slope \( r \) and a positive intercept \( E \) on the V-axis, which is the graph of Option (1). The graph does not pass through the origin, since the terminal voltage is \( E \) even when \( I=0 \).