If the current carried by a conductor is doubled, what...

If the current carried by a conductor is doubled, what happens to the (a) charge carrier density? (b) current density? $(c)$ electron drift velocity? (d) average time interval between collisions?

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Key Concepts

Average Time Interval Between Collisions

Also known as the mean free time, this is the average time between collisions of electrons with the lattice ions in a conductor. It is a material-specific parameter that depends on the interactions within the material and is independent of the magnitude of the current, so it remains unchanged when the current is doubled.

Electron Drift Velocity

Electron drift velocity is the average velocity at which electrons move through a conductor due to an applied electric field. In the relation I = n q v_d A, if current I is doubled, while n (carrier density), q (charge), and A (area) remain fixed, the drift velocity v_d must double accordingly.

Current Density

Current density is defined as the current per unit cross-sectional area of a conductor. Since the area remains constant, if the current is doubled, the current density also doubles.

Charge Carrier Density

This is the number of free charge carriers (like electrons) per unit volume in a conductor. It is an intrinsic property of the material and does not depend on the current flowing through it, so doubling the current does not alter the charge carrier density.

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