A conventional current of 12 A runs to the right in a...

A conventional current of 12 A runs to the right in a horizontal metal wire. (a) How many electrons pass some point in the wire per second? (b) In what direction are the electrons moving? (c) The electron mobility in this metal is $2.1 \times 10^{-4}$ $(\mathrm{m} / \mathrm{s}) /(\mathrm{N} / \mathrm{C})$ and the electric field in the wire is $0.15 \mathrm{N} / \mathrm{C}$. What is the average drift speed of the electrons?

Key Concepts

Conventional Current vs Electron Flow

Conventional current is defined as the flow of positive charge, while in conductors, the actual charge carriers are negatively charged electrons. This means that while the current is considered to flow in one direction, the electrons themselves move in the opposite direction. Understanding this distinction is crucial when solving problems involving current direction and electron motion.

Charge of an Electron

The concept of the elementary charge is pivotal when relating the amount of current to the number of electrons flowing. Each electron carries a fixed charge, and using this value, it is possible to determine the number of electrons that constitute a given current by dividing the total charge per second by the charge of one electron.

Drift Velocity and Electron Mobility

Drift velocity is the average velocity attained by charged particles, such as electrons, due to an electric field. Electron mobility quantifies the ease with which electrons can move through a material under the influence of an electric field. The drift velocity can be calculated by multiplying the electron mobility by the electric field strength, linking the material properties to the observed current flow.

Electric Field Influence on Charge Carriers

The electric field within a conductor applies a force on the charge carriers, causing them to drift in a direction opposite to the field if they are negatively charged. The magnitude of the electric field directly affects the drift speed, as higher fields result in greater acceleration of electrons, within the limits imposed by the material's properties such as mobility.

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