Question

How do you verify that resistance of a conductor is proportional to the length of the conductor for constant cross-section area and temperature?

Answer 1

Resistance of a conductor means the hindrance produced in the flow of electrons or in current flow. So, naturally the more the length of the conductor the more will be the resistance offered keeping area of conductor constant and at the same temperature.

For verifying this, take a wire of length $l$ of some area and find its resistance $R$ at some temperature and again take a $2l$ length of the same wire at same temperature, the resistance will come as $2R$.

Hence, $R\propto l$ at constant temperature.