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Current and Drift Velocity

Electrons are moving around randomly in the metallic lattice at very high speed. When a potential difference is applied all the free electrons drift slowly towards the positive terminal at once.

A formula for electric current in a metal is:

I = A n e vwhere I = current, n = number density, v = drift velocity of electrons, A = cross-sectional area of the conductor and e = charge on an electron 1.6 × 10^-19C.

The narrower the cross-sectional area of the wire the greater the drift velocity must be for the same current.

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Specification: OCR Physics A (H156), AS-level, 4.1.2 Mean drift velocity. Topic: Electricity.

Key terms in this lesson

energy: The capacity of a system to do work.
kinetic energy: The energy an object possesses due to its motion.
power: The rate at which work is done, or the rate of transfer of energy.
progressive wave: An oscillation that travels through a medium or space, transferring energy from one place to another without transferring matter.
amplitude: The maximum displacement of a particle or wave from its equilibrium position.

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