A metal conductor carries a steady direct current. Answer the following questions related to the flow of charge carriers in the conductor.
(i) Define electric current.
(ii) Explain, without performing any numerical calculation, what a constant value of current implies about the rate at which electrons cross any fixed cross–section of the conductor.
(iii) Discuss qualitatively how the number of electrons crossing the cross–section in one second depends on the magnitude of the current and on the elementary charge e. What would happen to this rate if the value of e were hypothetically doubled while keeping the current unchanged?