A resistor connected to a battery is heated due to the current. The quantity which does not change is

number of free electrons

The correct answer is Option (2) → number of free electrons

Explanation:

When a resistor is heated, its temperature increases, causing:

• Drift speed of electrons to change (due to change in resistance).

• Conductance to change (since it depends on temperature).

• Resistivity to change (it increases with temperature for metals).

However, the number of free electrons in the conductor remains constant because it depends only on the material and its atomic structure, not on temperature.