Choose the wrong statement:

The correct answer is Option (2) → Internal resistance of the cell decreases with decrease in temperature of electrolyte.

A real cell has an internal resistance \( r \), the resistance offered by its electrolyte to the flow of current. When a current \( I \) flows out of the cell, part of the emf is used up across \( r \):

    \( \displaystyle V = E - I r \)

The electrolyte conducts by the motion of ions, and the ions move more slowly in a colder electrolyte. So the internal resistance increases when the temperature of the electrolyte decreases.

Option (1) Potential difference across the terminals of the cell in a closed circuit is less than its emf. — True statement. On discharge \( V = E - Ir \), so the terminal potential difference is less than the emf whenever a current flows.

Option (2) Internal resistance of the cell decreases with decrease in temperature of electrolyte. — Wrong statement. Cooling the electrolyte raises its resistance, so the internal resistance increases, not decreases, as the temperature falls. This is the answer.

Option (3) Terminal potential difference versus current graph for a cell is a straight line with a negative slope. — True statement. \( V = E - Ir \) is a straight line in \( I \) with intercept \( E \) and slope \( -r \), which is negative.

Option (4) Terminal potential difference when cell is being charged V = E + Ir. — True statement. While charging, the charger drives current into the cell against its emf, so it must supply \( E \) plus the drop across \( r \): \( V = E + Ir \).